# Anti ventilation plate height



## scoobeb (Jun 15, 2015)

Ok,I have a question here,need some advice please. I have noticed my anti ventilation plate height is around 1 -1/2 inches below the bottom of my 1648 flat bottom jon boat. Is this correct? I'm fairly certain every jon boat has been the same that I owned but I have read were it should maybe be higher. I have seen like 50/50 jon boats were some were like mine and some were a bit higher as in close to even with the bottom of the boat. Does anyone else's outboard do this. I'm sure I'm just over analyzing the situation and it's probably no biggie unless it was a speed boat or performance boat but any info would be helpful,thanks.


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## DaleH (Jun 15, 2015)

Through the years I have found the info that is well described in this link to be spot on:

https://www.veradoclub.com/index.php?topic=137.0

The post shows pictures of larger V6 motors, but the info applies to all boats and OBs. It should be a sticky!

FYI - *if the post doesn't link automatically *... copy and paste it into your browser to connect.


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## Bowhunter1661 (Jun 15, 2015)

I have a Lowe 1440. My current motor is a 1988 Johnson 25. At this time my motor is raised off the transom a 1/2". This puts my anti vent plate dead even with the bottom of the hull. I have not been able to check where the motor rides on the water when cruising due to the fact last time I was out there were 3' waves on Lake Michigan so I couldn't really turn to look. (Though I did turn back to the harbor shortly after spearing a few waves..) . IMO, it is more a matter of on plane cruising and where your anti vent plates sits while on plane. If you have a stern heavy boat you may need to have it higher up due to the stern sagging deeper into the water. My boat sits almost perfectly level with the TM battery under my front deck.


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## scoobeb (Jun 15, 2015)

Well I just read my manual and it says around an inch below the keel is fine. I will just have to see how it performs on the water first. If I get near 30mph with one or two people and gear then it's riding right,I will also try to keep an eye on the anti ventilation plate while going wot to see were it rides,I'm betting it will be ok. I just double checked,it's around an inch and a half at the most,like I said,I still need to run it first,it maybe fine. I see tons of flat bottom jon boats like this and they run great.


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## DaleH (Jun 15, 2015)

Bowhunter1661 said:


> IMO, it is more a matter of on plane cruising and where your anti vent plates sits while on plane.


That is *the superior method* for setting an OB motor height ... 

And I'll add, provided that your boat is properly pitched to boot! That link I provided also tells one how to make sure they are wearing the right prop by testing the rig at WOT ...even if you never run it there. _It's akin to driving a car with the transmission set into the proper gear._

My biggest boating pet peeves are:

*1) *Most boat dealers rig the OBs too deep

*2)* Most OBs are rigged with the wrong (stoo steep) a pitch prop


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## scoobeb (Jun 15, 2015)

I went to my local marina and asked the same question there i did here.They said there should be no issue with an inch to even 2 inches below the keel on a light aluminum flat bottom jon boat.It's roughly around 1.5 inches under the keel give or take a mm.He told me most jon boats he has seen that he's come across his marina are that way.He told me i could move it up to make it even on the bottom if i wanted but the performance gained would be so minimal i probably wouldn't even notice.He said i should be near 30mph or better with this new motor with the 12 pitch prop i'm running.I take his word for it.He said just play with the tilt and get the best performance out of it.He said i'm over thinking it and it's no issue at all.Almost all the small outboards he said they install always sit a bit below the keel.He said if were talking inches as in 4 or 5 then we have an issue but a inch will not hurt it a bit.


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## DaleH (Jun 15, 2015)

scoobeb said:


> ... said if were talking inches as in 4 or 5 then we have an issue but a inch will not hurt it a bit.


Yes, the probability is that it won't hurt ... but for those of us who tweak our rigs, we're seeking optimal performance! 

Might not matter on light tin boats, but I know that when I ran a 3-ton rigged tuna boat, I was able to tweak out > 20% fuel economy and performance vs. other comparably equipped, but not optimally tuned rigs. 

A 10 to 20% improvement, when you're talking 100+ gallons of fuel per trip, is major $$$ when fuel is at $4+ per gallon _on-the-water_ co$t.


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## Skiffing (Jun 15, 2015)

Another consideration for better engine height is fuel consumption.

If you are cruising any distance having the engine height correct will save considerable fuel.

Boat stays on plane at lower RPM w/ similar speed.


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## huntinfool (Jun 15, 2015)

DaleH said:
 

> Through the years I have found the info that is well described in this link to be spot on:
> 
> https://www.veradoclub.com/index.php?topic=137.0
> 
> ...


Thank you for this. I've had issues and had just posted a pic of mine. Now I know.


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## scoobeb (Jun 15, 2015)

Yes,that makes perfect sense with fuel consumption on a rig using hundreds of gallons of gas. I use a six gallon fuel tank and never go over a mile offshore. I do go like 5-10 miles down the shore line but never out in deeper water. 3-4 foot is my average depth. I will gps it to see what my wot speed is. If I get near or at 30mph that is plenty fast enough in a tiller jon boat. I will see how it runs,if it's dragging bad then I need to raise it up for sure. I have had many jon boats and they all were like this and ran fast. I just never put any thought into it like now. If it's dragging it will be slower than I expect and run like crap. I got this motor for running all over the place and to get on plane with 3-4 people if I ever have that many on board which is rare.


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## Charger25 (Jun 16, 2015)

scoobeb said:


> Ok,I have a question here,need some advice please. I have noticed my anti ventilation plate height is around 1 -1/2 inches below the bottom of my 1648 flat bottom jon boat. Is this correct? I'm fairly certain every jon boat has been the dame that I owned but I have read were it should maybe be higher. I have seen like 50/50 jon boats were some were like mine and some were a bit higher as in close to even with the bottom of the boat. Does anyone else's outboard do this. I'm sure I'm just over analyzing the situation and it's probably no biggie unless it was a speed boat or performance boat but any info would be helpful,thanks.




All mine are like that 1 to 1.5 below the bottom of the boat. Its not that big of a deal. I must say though I have been kicking the idea around of getting a jack plate for the 16' All I need is about 2 more mph to out run a couple of friends boats, we're all running 25's and run the same speed :mrgreen:


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## scoobeb (Jun 16, 2015)

What kind of wot speed are you getting Charger25 with the 25hp? I just got the new 25hp efi suzuki and it's a cherry. It's a state of the art outboard,light and from the videos I have seen extremely powerful. I can't wait to get it on the water next week. I'm putting a new removable 1/2 -3/4 inch thick carpeted floor in it. I'm going to wait till fall to mod it out,to hot here in Florida to work,fishing ok but work forget it now.


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## huntinfool (Jun 16, 2015)

scoobeb said:


> What kind of wot speed are you getting Charger25 with the 25hp? I just got the new 25hp efi suzuki and it's a cherry. It's a state of the art outboard,light and from the videos I have seen extremely powerful. I can't wait to get it on the water next week. I'm putting a new removable 1/2 -3/4 inch thick carpeted floor in it. I'm going to wait till fall to mod it out,to hot here in Florida to work,fishing ok but work forget it now.


Adding that much carpet and floor will add a lot of weight. Just saying.


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## scoobeb (Jun 17, 2015)

Every jon boat I've ever owned I put a thick carpeted plywood floor in and it never effected the wot speed ever. It may add around 50lbs for the floor,give or take a little weight,that won't slow a flat bottom boat down imo at all at least in my experience.


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## scoobeb (Jun 17, 2015)

Well after reading and reading I'm going to get a 1x1 piece of wood to put under the outboard to lift it at least an inch orso. II'm wondering if the wood will rot out,I never had to do this before so it's all trial and error. Plus it will be sitting off the transom so will the clamps hold it down the same? If the motor runs good like that then I plan on bolting it in but for now I'm using just the clamps. Will the wood work ok and the way I plan on doing this,please any help on this chime in,thanks.


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## Charger25 (Jun 17, 2015)

scoobeb said:


> What kind of wot speed are you getting Charger25 with the 25hp? I just got the new 25hp efi suzuki and it's a cherry. It's a state of the art outboard,light and from the videos I have seen extremely powerful. I can't wait to get it on the water next week. I'm putting a new removable 1/2 -3/4 inch thick carpeted floor in it. I'm going to wait till fall to mod it out,to hot here in Florida to work,fishing ok but work forget it now.




The 16' is a semi-V . V bow ending in a flat stern with rounded chines. It's a bare bones boat,the bench seats are carpeted with clamp on style jon boat seats. If im running solo the motor is trimmed all the way in, if some one else is in it i'll trim it out a hole or two. Either way it will run a solid 30 mph according to the gps.
One of the guys has a new 25hp 4 stroke electric start Suzuki on a 14' dbl wide mod -v , Thats the fella I wanna out run


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## Bowhunter1661 (Jun 17, 2015)

I currently have my motor level, using one 1/2" shim. My anti vent plate still digs in the water. Personally, I do not feel comfortable raising the motor more than an inch to a half inch. The clamps start getting too close to the top of the transom for my comfort. Therefore, I made a jack plate to raise it to aprox 1-1/2" off the transom. Also, with the 4.5 inches of setback I may be able to go up to 2-2 1/2" off the transom.


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## scoobeb (Jun 17, 2015)

Well Charger25 that is funny I have the same motor. Maybe I'm just over thinking this and should leave it alone if I get near 30mph. My boat is the 1648 flat bottom alumacraft with the 25hp efi suzuki tiller. The boat is light at only 290lbs and I know it doesn't take much to move them. I guess it makes sense to see how it performs first,after all 30 mph is fast in a tiller flat bottom jon boat. The main thing is if I leave it the way it is will it hurt anything? Now if I go out and do like 15-20mph then I know it's just plowing and needs to be raised. If your rig is doing 30mph then I would think mine would also. I called the place were I bought the boat and they told me near even with the bottom of the boat of a bit under is ideal but he said the way I have it won't hurt a thing but it could pull to one side and ride a bit weird,other then that it would be ok. Like I said if it runs like crap I will put a 1x1 shim under it to fix it.


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## scoobeb (Jun 17, 2015)

I figured i would just post pictures,that would give everyone the exact height it's at.The issue i have is i'm not working with to much more movement on the clamps.I can probably move it up a half inch or so but there is not much room for allot of movement as you can see.I have the clamps holding it on now as well as 4 zip ties so the clamps won't ever turn to loosen it up.I was going to put a long lock in the holes of the plastic turn handles but i remember how annoying the vibration was so i decided to go with zip ties with no noise.Here are the pictures and please let me know if i'm just to paranoid over this and it will be fine or i do have something to worry about.My manual says from even with the bottom of the boat to a inch is fine,i'm about a half inch off the mark as i measured it.It's around 1 1/2 inches under.This is a light jon boat at around 290lbs so i would think this motor should scoot this boat every bit of 30+mph.Ok, please let me know what you think,thanks.


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## Bowhunter1661 (Jun 17, 2015)

Personally I would say you have nothing to loose by raising the motor and only more to gain. Though it likely performs good at that height it very well may perform even better if the height is raised. Possibly a couple mph, maybe only 1 mph? Possibly better fuel consumption? Ods are at that height your anti vent plate is plowing, if that is the case I personally would suggest raising your motor. Many may say leave it. But I am a perfectionist. If my boat isn't in perfect tune i am not happy. That is why I am at this very moment installing my homemade jack plate, to perfectly fine tune the height of both my 15 hp and 25. Without the fear of my motor falling off because it is too high on the transom.


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## Skiffing (Jun 17, 2015)

FWIW

As soon as the water clears the stern it rises up.

The cav plate is submerged 1.5" - 2" in the best conditions.

That's a lot of unnecessary dag & resistance. 

If you do use a jack plate as Bowhunter has done you will have to raise the engine even higher to gain performance.

The performance is not just speed. It is lower drag - rpm, better fuel efficiency and prop clearance, etc.....


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## turbotodd (Jun 17, 2015)

DaleH said:


> My biggest boating pet peeves are:
> 
> *1) *Most boat dealers rig the OBs too deep
> 
> *2)* Most OBs are rigged with the wrong (stoo steep) a pitch prop



Ever wonder why dealers do that? Liability. And I have been down that road. Rigged a customer's brand new duck boat the exact same way that mine is, which is conservative but performs well (but not as well as it "could" ). Guy owns it about a week, calls me says it runs like poo after a few minutes of run time. He drops it off, I run it over to the lake, ran it about 15 minutes at full throttle 6000-6050 RPM and never missed a beat. Checked all fluids, checked impeller and key, etc. Found nothing. Told him I couldn't find anything wrong. It's duck season, guy runs it. Brings it back, low compression on top cylinder. Been hot/overheated. I start asking questions and find out that he's running 4 people in the boat, him in the back and 3 in the front. At full throttle it was pulling the foot up out of the water far enough to let the water pump ventilate but he keeps running it because it's duck season and the world will end if they don't have a boat to hunt out of. So in short, we ended up buying the guy a new powerhead. After installing, I dropped the motor back down on the transom (from a 3" lift), which put the AV plate at zero. Trying to get the guy the best performance possible ended up costing us about $1500.

Agree with most guys putting too much pitch in the prop on initial setup. Even Yamaha sometimes suggests more prop than that particular rig can handle. I see it listed on their performance bulletins and sometimes they'll list RPM tested at 5600 or something like that. An inch less pitch would help a ton, IMO, in cases like that. Those performance bulletins are real-world tests that dealers have supplied the info for. Other reason is that if a boat builder/rigger puts an inch more pitch than he knows is optimal, he more or less reduces the chances of over-rev, say, if Mr. Customer decides to ditch a battery or two, the trolling motor, etc...to see how fast it'll go. In the case of 99% of the boats that I've sold, nary a tach gets installed so guys can very easily twist the motor up well beyond what it's designed for. So lot of times we'll suggest using 12" pitch where an 11" would be optimal. Or if they choose 11" we'll tell them that it's optimal with a certain load. Less load=more pitch and more load=less pitch. One prop won't do it all but a lot of people will try. Props are, after all, kind of expensive. I have two. A 11" SS that I normally run, or if my GF and I go together, I'll put a stocker 10.5" pitch back on. Gets out of the hole faster, which is kind of important because she has to take everything (including the kitchen's sink) with her when we go fishin. It don't matter to me much...I'm just happy that she enjoys going.


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## scoobeb (Jun 18, 2015)

Ty all for the info,helps allot. What I did was go back to look at pictures of were my other motors were mounted on the back of my other jon boats,what I found was interesting. All,I mean all my outboards were at the same level or even lower than mine is now and they all performed well like that. I always hit a great over all top end speed and hole shot was superb. Honestly if I'm losing a mph or two I'm not overly concerned about that,if I get near 30mph like I said that is extremely satisfying to me,any faster on a tiller motor is scary anyway. I may just be over thinking this as it should perform great as all my others did. If it doesn't than I will worry about it. I was going to move it up an inch till I saw I had little clamp movement left. If I must do a jack plate then I will. I don't need perfect,it's not a speed boat,lol. I would like it to perform good though and if it does as it sits I will leave it.


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## scoobeb (Jun 18, 2015)

Here are some pics of one of my other boats i had,look closely at the anti vent plate here,it's near as low if not lower then the one i have now and that was a 15hp as all i needed to do was change out the reed valve from the 9.9 to the 15 reed valve to make it a 15.This boat with me and my ex wife and my child did over 22mph and the hole shot was good for a under powered boat rated for a 25.No problem with this one.I looked at all my boats i took pics of and they all hang below the bottom of the keel on all 5 of them at least an inch or 2 and all performed extremely well.I think it will be fine as is but again if it doesn't work as it should then i will at least know what the issue is.I'm putting a 12 pitch prop on it to.It came with a 11pitch prop but from all i have read this motor has mega power and will more then likely over rev with the standard prop so i went up a size.I will report back as soon as i take it out to test run it.My local lakes ramp is closed due to making it better so i'm going to have to wait for a nice windless day to test it out right.Here is the pics i'm talking about,thanks.


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## scoobeb (Jun 19, 2015)

turbotodd said:


> DaleH said:
> 
> 
> > My biggest boating pet peeves are:
> ...


So with all that your telling me to leave it as be and enjoy my boat. If I get good performance were everything is I'm leaving it as be. From all I read it won't hurt anything like it is. I don't need to gain a mph or two if it performs well already. I will test it here soon and if It really suffers on performance then I will do what needs to be done to correct it. I realize it's not a speed boat,lol.


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## Bowhunter1661 (Jun 19, 2015)

You can make what ever end decision you like. My boat performs fantastic with my current engine height. It runs 32 MPH turning 5400 rpm WOT on a 1440 Lowe, 1988 Johnson 25. Also it sips fuel now with the anti vent plate completely out of the water.


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## scoobeb (Jun 19, 2015)

Would you mind posting good pictures of the whole homemade Jack plate you made so I can get a idea how to put it together if I need to do so? Your boat is a hair over 200lbs,I was going to buy one a while back and had I known how crappy this alumacraft was built I would have bought a new lowe 1648. I've had awesome luck with all the alumacraft jon boats I have purchased until this one. My boat is I believe 290-310lbs so with this 25hp I should get near or close to 28-30mph with one or two people in the boat. If I hit that I'm completely satisfied,if I hit say like 22-25mph then I know there is a problem with the way it's set up and needs height adjustment.


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## Bowhunter1661 (Jun 20, 2015)

At the top of page two there are two pics. Unfortunately those are the only ones I have at the moment. I went to the local steel supply company. Bought 4 feet of 3"x3"X1/4" aluminum angle. I had them cut it into four sections 12" long. Though I did end up cutting them down to 10" each. 

Here is where I got my idea. This guy did a great job showing the build process.
https://www.theonlinefisherman.com/forum/index.php/topic/13203-how-to-build-your-own-jackplate/


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## scoobeb (Jun 20, 2015)

Your running your anti ventilation plate dead even with the bottom of the boat while getting your current speed? I can just use a wood shim and move it up darn close to where the anti ventilation plate is level with the keel. I am going to get a shim today to see how it sets. I can probably move the motor up at least 3/4 to 1" if needed. First is first,I need to test run it before I do anything because it may run awesome as is,you never know.


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## Bowhunter1661 (Jun 20, 2015)

I have mine set approximately 1.5-2" above the transom. But, I have the jack plate. With the the plate it gives your motor setback, aprox 4 1/2" on mine. This allows me to raise the motor even more that is it were raised on the transom because as the water flows under your boat it starts to rise immediately. Allowing higher motor placement. Since this pic I have actually raised the motor anoth 1/2".


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## Bowhunter1661 (Jun 20, 2015)

Never mind all the crap in the background. I live in a condo and my neighbors think their garage is a scrap yard.


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## scoobeb (Jun 22, 2015)

Well,here is what I'm deciding to do,makes logical sense since I'm going to keep this boat for many yrs. I'm going to sell this motor since it's brand new abd buy the same outboard. This time though I'm getting the whole package,electric tilt and trim,electric start this way no need for a jack plate and not thinking how hard it will be to tilt a 136lb outboard is worth the upgrade. The price difference of $400 is well worth it to me. No a question,how much trim do these outboards really go? If I was say were I'm at now 1-2 inches below the keel would a power trim system move me up at least the couple inches I need? If it wouldn't then this would be worth the money. I guess what I'm asking is how many inches up or down does a power tilt and trim system give you?


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## Bowhunter1661 (Jun 22, 2015)

If you really want tilt trim I would say that would be a good route to go. However, IMO (and I'm sure others will vary) that is not going to be your saving grace when it comes to the motor height. If you simply trim up with incorrect motor height it will cause more drag as your anti vent plate is now angled down below the surface of the water. It is a combination of engine height and tilt. For example, my AV plate sits exactly where you want it when cruising (level and out of the water), however, when accelerating I get a slight bit of ventilation with the motor in the third pin from the transom. If if had tilt/trim I could trim the motor all the way down, get on plane, then trim it up to get the anti vent plate out of the water. That is the optimal situation. 

With your current motor height I feel your anti vent plate will still be submerged even with your motor tilted with Hyd tilt/trim. 

Now, say you go the route you are speaking and trade the motor in for a Hyd tilt trim model. I would still suggest you either buy or make a jack plate. The way I see it is your leaving chips on the table. You have invested a lot of money in a little Jon boat, why not make it perform as best it can. The marketed plates aren't all that expensive, I just love building things. That's why I made my own.

I do plan on building my own tilt trim unit so I can take of fully trimmed down to eliminate ventalation, then once on plane trim up to get the plate even with the water. If I run with my trim down, even with my current elevated motor height, the anti vent plate digs in. I have to be trimmed in the third hole so the anti vent plate is level when on plane.


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## scoobeb (Jun 22, 2015)

So you don't think power trim would move my motor up far enough to at least be even with the keel,I'm only 1-2 inches from being even with the keel,I don't see how that wouldn't do it. What's the purpose of selling an outboard with power tilt and trim if it wouldn't trim to the right height,that would be useless.


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## JL8Jeff (Jun 22, 2015)

Power trim only tilts the motor, it does not raise the motor height when running. You would need a jack plate to raise the motor higher while running.


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## scoobeb (Jun 22, 2015)

Ok,now I'm really lost here. I thought trim was up and down for engine height and tilt was tilting the motor up and down out of the water. How can they advertise power trim and tilt if they are the same thing. That wouldn't make any sense,you know what I mean?


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## Bowhunter1661 (Jun 22, 2015)

Trim is what you use when on plane or taking off from a stop. It adjusts about 1-3" I would say depending on model and engine size. 

Tilt is used when removing boat from water to get the motor up high, or when installing a transom saver. Tilt kicks in when trim is at the top of the trim ram stroke, so aproximatley 1-2" -6-8" high. 

Here is a hydraulic tilt/trim for a larger outboard. The trim raises, once that is maxed out the tilt raises the rest of the way. On a smaller out board I believe they only have one cylinder, this would be a combination tilt/trim. Likely to raise the motor from 0"-6" depending on length of the cylinder rod.


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## scoobeb (Jun 22, 2015)

You know what's funny,what's the point in a short shaft outboard on a short shaft transom if it doesn't work right. That is extremely pointless. Almost all the boats I have watched on YouTube bigger and smaller have most of the av plates riding under the water,no I don't doubt for a minute it does cause drag but how much is really is unknown especially ona jon boat. I watched a few ppeople who got the height exactly right on their boats and they posted it made only a slight difference in speed and fuel consumption but they did say it helped very little. I know now that it won't hurt it any,it may knock a mph or two of my top end which is not a big deal. But I'm starting to understand the whole drag issues. I can see how it would help on a boat with a larger outboard that takes allot of fuel to run through out the day but imo if my boat does well what's the point in modifying the transom for so little gain. Like I said if it's a big issue andIit performs like poop then I will fix the issue. Still to me spending the extra money is worth it just to save my back.


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## Bowhunter1661 (Jun 22, 2015)

This is a small outboard tilt/trim cylinder. Likely similar to what the outboard you are looking will come with.


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## Skiffing (Jun 22, 2015)

Trim is going to change the angle of the prop THRUST in relation to the hull. It's not going to compensate for too long or too short a shaft.

You'll still have the same issues you have now. Wouldn't rather have the prop pushing the boat forward instead of lifting or burying the bow? 

Power trim is a good thing, though. Among other things - it will allow you to trim up and find the sweet spot for cruising, trim down if you porpoise in a chop, get a better hole shot, etc, etc.


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## scoobeb (Jun 22, 2015)

This is what I do know,I can put a 3/4-1 inch shim under my motor now to get the av plate almost close to level with the keel,I think I would be comfortable there. I won't go any higher because I don't want to chance the motor over heating even it may never over heat with it higher. I can't see how this motor wouldn't perform well if the av plate was really close to dead even of the keel give or take a cm. I know my manual says do not go any higher then level with the keel. It says anything from level to one inch down is were it needs to be to perform at it's best,that is in my manual. Maybe I will just deal with the motor the way it is and put just a shim under it. I figured a small wood shim would do it,then I will clamp it down hard and go test it out,if it works well I will just bolt it down. One more thing,when I opened the box there was only two bolts for mounting the motor,is there any advantage to using the top or bottom holes? I guess two is enough because they supplied the hardware.


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## Skiffing (Jun 22, 2015)

scoobeb said:


> snip// ..... I watched a few ppeople who got the height exactly right on their boats and they posted it made only a slight difference in speed and fuel consumption but they did say it helped very little.// snip.



It may not be worth it for you to do anything!

Speed performance gains on boats like ours will be minimal. Fuel efficiency will be increased though. I doubt most guys in small boats meter their fuel use or know what the GPH consumption is at any RPM. It's not like you've got twin 454's that gulp 35 gallons per hour [EACH] 

In my case - I tweaked the engine height a few times and can now cruise at 24mph @ 4700 RPM. WOT is 29mph @ 5600 RPM. Fully loaded boat is 1360 lbs. Fuel burn is 7.5 miles per gallon. Merc publishes 4.8 gallons / hour @ 6000 RPM for my engine. This tells me I'm getting good efficiency.

Lots of guys could care less about this - they want to fish and enjoy. For some of us, though, this is part of the fun.


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## scoobeb (Jun 22, 2015)

I will make 1/2. 3/4 1. Inch shims to see what works for the best height without going higher then the keel,I just hope I have enough transom left to clamp . I found quite a few forums I just read were guys just lifted their motor with wood shims like I want to and just used the clamps and never bolted it down and they never had any issues. Now of course if I do this I will still have that cable lock to make sure if it ever popped up it would get caught by the cable. When I clamp it down,I clamp it down,it would take some extremely serious force to pop the motor off the transom.the good part is if I move the motor up the clamps will be actually be sitting under the lip of the top of the transom for extra security. So all in all I believe I will try that first,shims.


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## scoobeb (Jun 22, 2015)

I'm one of those people who loves watching the boat videos on YouTube,I love watching them. Almost all the small jon boats like ours run with the av plate under the water and they still run fast. I never said that was right but most If nit all those people are not educated like myself being uneducated on how to perfectly tune an outboard. I see your point though,I'm only going to get so much speed and performance out of a jon boat. I'm not to overly concerned about losing a mph like I said but it would be nice to have electric start and power trim and tilt for only few hundred more. I should just say screw it,mount the sucker on and go fishing,but this is in my head now and my ocd is kicking in,lol.


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## Bowhunter1661 (Jun 22, 2015)

I am just one of those crazy fellows that loves to tinker with my boat. If there is even one thing I can POSSIBLY make better, I m doing it! To each his own, this is just my .02 cents. My boat performed well when I had zero adjustments made to it, now it performs great. I get a lot of enjoyment and satisfaction out of perfecting my setup.


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## Skiffing (Jun 22, 2015)

^^^

If you're not anal you're not a good hunter


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## scoobeb (Jun 22, 2015)

Well here is my plan,buy 1/2-3/4-1 inch shims,use the one that gets me dead even with the keel of the boat which should give me the best performance,clamp on the engine as much as I can,stop thinking about this anymore,enjoy my boat and go fishing. :mrgreen:


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## Bowhunter1661 (Jun 22, 2015)

If this helps at all, here is where my motor is at with the jack plate. However I did raise it another 3/4" from this point to get it right on.


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## scoobeb (Jun 22, 2015)

Like I said I will lift mine as high as the transom will let me with having enough bite for the clamps to lock down on. Then I will just use it and be happy. Unless it just performs horribly I will leave it as be. As long as my wot with one or two people is near 30+mph I will be ecstatic and satisfied.


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## Bowhunter1661 (Jun 22, 2015)

Wonderful! Enjoy!


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## scoobeb (Jun 23, 2015)

I saw your video on YouTube,pretty cool. So what kind of wot are you getting to see if I'm in the same ball park. My boat should scream with this new 25hp. I'm hoping 30-33mph with one person and at least 28-30mph with two people.


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## Bowhunter1661 (Jun 23, 2015)

Yeah that video was horrible, you kind of have to lay your phone flat and turn it to view correctly. Still trying to get use to this new phone. If you don't have casting decks or all the bells and whistles I have that sounds like a realistic speed. After all, my Boat is loaded to the gills and I saw 32 mph show up on my GPS but I could cruise all day at 31.


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## Bowhunter1661 (Jun 23, 2015)

But I should also add that I am running a 15 pitch prop and turning 5400 RPM at WOT.


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## Charger25 (Jun 23, 2015)

10 X 15 ? you guys are make me buy a new prop and buy/ build a jack plate before it over :LOL2:


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## Bowhunter1661 (Jun 23, 2015)

Charger25 said:


> 10 X 15 ? you guys are make me buy a new prop and buy/ build a jack plate before it over :LOL2:



Lol, I was shocked when I bought this motor to see a 15" prop on it! But it turns it great! The added height certainly helps with getting the RPMs up


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## Bowhunter1661 (Jun 23, 2015)

Also, I may or may not be ordering a 35 carb and intake for my motor. 8)


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## scoobeb (Jun 23, 2015)

I have watched so many videos my head is spinning,lol. Over 95% of the people that own jon boats run with the anti ventilation plate under water and almost all the rigs fly except for the ones that are way underpowered. Most of the guys trying to get their height right were large boat owners. Like I said though most of the videos had the plate buried but still flying on the water. Yours was about the only fine tuned outboard out there. So now if say I move my engine up to even with the keel by putting a shim under the engine and run over 30mph wouldn't that be great considering your rig is as fine tuned as you can get and your prop is a 15 pitch so it's 3 pitches bigger then mine. I would be good then,right?


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## scoobeb (Jun 23, 2015)

There is a website called media channeslblade.com that explains about engine height. It states that standard height is 1-2 inches below the keel for slow speed as I would guess our boats,under 40mph. Then it has even with the keel for average speed,also our boats I would guess again under 40mph,then you have 2-4 inches above that states high performance speed boats. So all in all 1-2 inches below the keel to even with the keel seems to be were most people end up setting their rig up.


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## Bowhunter1661 (Jun 23, 2015)

At that point, yes, I would call it good. The reason I can raise mine so high is due to the setback the jackplate gives me. When the water passes under the boat and exits behind it immediately starts to rise, due to the fact your hull displaced it. Yours being mounted directly to the transom with no setback should be just fine at even with the transom. Possibly a little digging in, but not a lot. 

My boat is heavier due to all of the accessories I have, including decks, trolling motor, battery ESC... Therefore when planing it does sit slightly deeper than an empty boat. That's why I need my motor to be higher, because my boat drafts deeper, as well as mentioned before. The water rises up to a higher level where my motor is setback to. 

Imagine this in your head. Your flying at 30 mph, boat is sitting level ON TOP of the water. Maybe drafting 1" when on plane. If the AV plate is level with the keel, the water is flowing Beneath the boat and slightly raising as it exits under your keel. You should be right on, or darn close with the AV plate adjusted level with the keel.


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## scoobeb (Jun 23, 2015)

So I'm going to use a wood shim,anything I should treat it with to last me a long time? Also I don't know if I have enough bite on the transom to go perfectly level with the keel but I'm going to get as close as possible. I may be a 1/4 inch off but that's better than were I am now.


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## Bowhunter1661 (Jun 23, 2015)

Would would work. Say that three times fast. But I would use something that will never rot. Like a cutting board. Buy a cheap on and cut 10"X1 1/2" or however thick your transom is. Then glue them together or screw them together. Presto, no rot. 

I plan on upgrading the 2x10 I used to a 15"x8" piece of 1/4" aluminum plate so I never have to worry about rot.


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## scoobeb (Jun 23, 2015)

Good idea,ha. I just bought 3 cutting boards at walmart. I will take a couple drops of crazy glue to hold the shim in place then drop the motor on top of it. Or I can just screw it in to the top of the transom,that won't ever move or rot with the hard plastic shim and ss screws,does that sound like a good idea?


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## Bowhunter1661 (Jun 23, 2015)

Sounds like a plan to me. Just put some silicone in the screw holes so water doesn't get into the board


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## Bowhunter1661 (Jun 23, 2015)

Or you could bolt your motor to the transom and go as high as you like. Even if the clamps only grab the top of the transom, put your shins in. Get your height right, then bolt it


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## scoobeb (Jun 23, 2015)

Well,I have to go to Walmart to get a solid cutting board,the ones I bought have like a lip around the whole thing to catch like liquid and stuff like that,I want a solid cutting board. So my plan is to cut out one shim at a time,stack one up,see were the clamps line up on the transom and the av plate,if I have more room I will go higher. I'm going to get as close as possible making sure I have plenty of clamp biting on the transom. Once I get the desired height then I will screw the plastic into the top and I will put a few drops of silicone in the holes to. I don't think water could get in there because it's on top of the transom but better safe then sorry. Just a thought,wouldn't the plastic eventually get brittle due to the outside elements,like sun,etc.....


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## Bowhunter1661 (Jun 23, 2015)

I suppose the cutting boards could get brittle. But I have used the cheap ones for fish cleaning and leave them out all year long and they never seem to change state. I have seen on numerous occasions where others have used plastic cutting boards for projects on boats and they are fine. 

Very curious to see how this goes for you. 

I also have a 9.9 for restricted lakes, I adjusted the motor up to the point my clamps had about 3/4" of bite on the transom. Now for a larger motor with more torque it may not me all that great but it worked fine for the little 9.9. I made my shims the exact thickness of the transom so that the clamps actually clamped down on the 1/4" worth of board they were touching. 

Ran that way for several months and never had the slightest bit of loosening of the clamps or movement. If I didn't have the jack plate I would have just got my height right and bolted it down. Certainly no worries about it comming off then. And no need for clamps.


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## Bowhunter1661 (Jun 23, 2015)

Ops I meant my clamps were attached to the transom 3/4 of the way. 3/4" is not a good thing.


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## scoobeb (Jun 23, 2015)

If you look at the pictures of my transom you will see there is a lip there,the clamps will actually slip under that lip so it's kind of like extra security. I may just leave it were it is now only if there isn't enough bite for the clamps when I put the shim under it. I think it will be fine either way but I may gain a little top end speed. Like one person said I just may be way over thinking this whole thing and should just leave it as be. It's not like it's several inches below the keel,it's around a inch or two at the very max.


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## scoobeb (Jun 23, 2015)

It's a light flat bottom jon boat,I think this motor will make this boat fly no matter what,that's just imo. I can live with it as long as there's no rooster tail and water coming in the boat. I just need to find a nice flat calm day and test it out to see were im at,if I hit 30mph or better I'm doing real good.


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## scoobeb (Jun 25, 2015)

So here is what I'm going to do. First ,cut out two shims made out of the cutting board as Bowhunter 1661 described,second,put the shims on one at a time then the motor to see how close I can come to level with the keel as I possibly can get. When I get the height right I will screw the shims in from the top to hold them in place so when I put the engine on they won't move. Third,mount the engine and go catch some fish. One advantage I get from putting the motor up an inch or so is more prop clearance from hitting rocks or oysters that I run near and over to fish at. I'm sure if I mount it on the transom and go it will perform great but why not do it right the first time. Now if I can't get enough of the clamps to bite on the transom then I'm just mounting it on the transom and going fishing,lol but I should be able to move it some with good bite on the transom. Thank you to everyone who has helped me,especially Bowhunter 1661,thanks. :mrgreen:


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## scoobeb (Jun 26, 2015)

Ok,I tried to move it up on the transom,problem is the clamps won't be under that lip and doesn't feel secure to me so scratch that idea. All I can do is lay it on the transom and go or get a jack plate for it. So now I'm stuck with a decision. I guess I'm going to mount it and go for now and hope for the best.


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## huntinfool (Jul 5, 2015)

I raised mine up a hole. But my question is should I just be on plane when checking or should I be wide open? 
Just on plane, mine is still under in front and a hair out in back. ( I know this is due to trim) We were fighting a good chop, so my wife didn't feel comfortable going wide open. 

Should I go up another?


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## scoobeb (Aug 24, 2015)

So I went back to the 20hp,the 25hp was just to much to handle without electric start or power tilt and trim. The 20hp is almost 40lbs lighter and so much easier to start and control. The 25 was a awesome motor but just to hard to start manually and was hard to tilt. The 20hp is perfect for a 16ft jon boat.


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