# Boat Plowing at full throttle



## Led_Junkie (Jul 29, 2013)

I FINALLY made it to the river and got underway on my maiden voyage of my 14' Polar Craft Semi-V and 25Hp Evinrude Sportsman ('72). The first shakedown trip revealed an issue that wouldn't allow me to motor faster than 2-3 mph, motor starts and runs great but couldn't throttle up. I found that the spark plug cable was routed in a way that it was binding on the the throttle linkage-Easy fix. Then we got going, up on plane, not real fast, but ok then high revs, and noticable decelleration. This was corrected by dropping the motor to the bottom pin. Quicker acceration, up on plane quick but once past the 3/4 throttle mark the boat begins to plow, throw bow wake, and become unstable. When one eases back on the gas the bow pops back up level and were skipping along nicely.

This was all with myself (220) 11 yo son, cooler, battery, trolling motor, 25lb worth of anchors and 6 rods and a tackle box. I had the gas can and battery with me in the stern, son was sitting center in the forward seat.

I initally thought the prop was spun since I could grab it and twist it about 1/4 inch in either direction (the cavitation issue). <Shrug> When I mounted the motor I placed a level along the bottom of the hull and tried to line up the caviation plate and the hull but ran out of transom. Could I have mounted the motor too high? I have been thinking of making a jack-plate from Aluminum angle as some have done but really have to wait to get funds.

I really need navigation lights first since it is at least running good up to 3/4 throttle. Any ideas would be welcome.

Thanks!


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## FerrisBueller (Jul 29, 2013)

Sounds almost to me that since you put the motor all the way down to the first pin position that once you get up and going, at a certain point the motor actually is starting to push the boat downwards too much causing the "plowing". Maybe try moving your motor to the second pin position?


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## PGRChaplain (Jul 29, 2013)

Move some weight forward and move the motor back a couple holes. Picture the motor angle to boat when the boat is on Plane. Sounds like the motor is pushing the Bow down as stated above.


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## cva34 (Jul 29, 2013)

Thats what I would do..All the way down will get on plane fast then start to plow.Get her loaded about even then try dif... hole tell it does what you want.


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## Led_Junkie (Jul 29, 2013)

Are you talking about the trim slots? Where the spring loaded rod gets threaded through the holes and the motor locks onto? If so then I origionally had the motor in the #2 hole position which would hold the motor in a less than vertical position. When I placed it (the rod) into the slot closest to the transom that is when it began to ride better then plow at top speed.

The motor only mounts via screw clamps so I cannot move the motor up and down on a track. I have run out of room on my transom to raise the motor but I have plenty of room to lower it. 

I'll have to grab some pics later, if I am mistaken.


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## FerrisBueller (Jul 29, 2013)

Right, there should be different holes where a pin goes through which allows the motor to rest at a certain angle. I think typically people set it to the second pin, but it depends on the loads. The higher up you set the pin the more downward thrust you will have on the rear.

What we were thinking with your is that being its set to the lowest pin position, once your boat planes there is less resistance on the boat and at a certain point the motor is actually pushing the rear upwards causing the front to plow.


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## Led_Junkie (Jul 29, 2013)

Ahh gotcha. I started out in the #2 hole, that is what gave me the "Cavitation" and surging and lack luster performance. Once I placed the motor in the lowest postion the boat ran great until the plowing started. 

Could this be from having the motor mounted too low?


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## Led_Junkie (Jul 29, 2013)

I see now...
So now I have to see why I am cavitating then...
Should a prop have any movement when turned by hand?


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## marshman (Jul 29, 2013)

something definitely sounds out of whack... can you take some pics and post them?? i have never had a boat that i had to run set on the bottom pin...youll never get any decent performance trimmed all the way down... 

either you have a weight balance issue, or transom isnt straight, or bad prop, or something...im gonna read back through your stuff...

you say cavitated on the second pin?? like prop blowout??( was going on plane, then revved up high but slowed down)

if you blew out, you may be too high(the motor setting that is!! :LOL2: :LOL2: )

second pin should not make you blow out... but the other end of the trim could make you blow out...

i think we need more info...


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## marshman (Jul 29, 2013)

if motor is too low, cavitation wont be the problem....it (the motor)will just plow water and be slow...


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## Led_Junkie (Jul 29, 2013)

I'll grab some pics when I get home. 

When I state that I was caviating it felt like it was surging, not the motor but the lower end/prop. I would hear a whooshing sound then the pitch would deepen and I could feel the power climb back up then whoosh/ vroom, whoosh...maybe I am high :LOL2: lol

When the motor was set in the first hole I got no noise and power was smooth until the plow @ 3/4. Before I reset the pin I grabbed the prop and gave it a twist back and forth and there was a measured movement back and forth about 1/4" or so.

I know nothing about outboards so this is all new to me but fun too  I like know how things work. Thanks for the help so far!


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## tomme boy (Jul 29, 2013)

Lower it on the transom all the way down and put the pin in the 2nd hole and just run it. You are way overthinking this.


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## Led_Junkie (Jul 29, 2013)

This is my problem I am sure. My transom plate is too short so it is causing the tilting of my motor. Back into the garage to recut and remount <sigh> and I used 5200 to seal the bolts up.


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## acwd (Jul 29, 2013)

Looks like the motor is too high the motor mounting clamp should be touching the top if the transom. 

Steve


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## marshman (Jul 29, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324171#p324171 said:


> acwd » 29 Jul 2013, 21:25[/url]"]Looks like the motor is too high the motor mounting clamp should be touching the top if the transom.
> 
> Steve




maybe...maybe an omc dont like to run high...mercs do...

what does the transom measure bottom to top/top to bottom...?? that may be the blowout issue..

when i first was commenting i think i had your rig mixed up with another on here..i thought for some reason i was talking to the guy with the long shaft motor on the transom riser.....


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## tomme boy (Jul 29, 2013)

The wood you have on the rear outside of the transom. OK it needs to go all the way to the top. That will tilt the motor back in a little. Now, Lower the motor all the way down onto the transom. Put the pin in the first hole. If it still starts to plow, check to see if the bottom of the hull has a hook. That might be why it it plowing and cavitating.


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## Led_Junkie (Jul 30, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324171#p324171 said:


> acwd » 29 Jul 2013, 21:25[/url]"]Looks like the motor is too high the motor mounting clamp should be touching the top if the transom.
> 
> Steve



This is another concern of mine. With the motor mounted this high the cavitation plate is still below the hull. I guess I will have to fabricate a jack plate. I'm going to stop by Fastenal on the way home from work and price a few pieces of Aluminum angle. thanks for the help so far thanks.

In the short term I'll keep the trottle down. It still scoots across the water nicely but I know it can do much better from reading other posts on boats my size with the same motor getting mid to high 20's

I'll keep updating things as I go. Thanks!


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## tomme boy (Jul 30, 2013)

It does not matter if the anti-cavitation plate is below the bottom of the boat. Lower it on the transom and replace the wood so it goes all the way to the top of the transom and try the different holes for the trim height. You are getting the cavitation from the motor being too high. This is not a bass boat and you do not have a prop made with a cup. If you are getting cavitation, you are also losing water to your water pump. 

Don't try to overthink this and save yourself some money. Post a picture with a straightedge down the length of the bottom of the hull at the rear. This will show if the bottom has a hook in it.


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## Led_Junkie (Aug 5, 2013)

Ok I added a temp piece of wood to the plate in the rear of the transom, and dropped the motor all the way down and set the motor in the 2nd hole position. I has thought you had said second but now read that you wanted it in the 1st position.

Performance was this: With same load the boat was much slower to get on plane, but then began to behave same as previously past 3/4 throttle and plowed. I had my son reposition himself in the middle, but the bow rode so high when taking off it was a bit unsettling. Once we planed out it was smooth and the plowing occured at the same speed, granted not as severe. He moved to the forward seat and the high bow problem was solved a bit but the plowing had increased as one would assume.

I didn't get to check the hull for a hook, but I'll try to get that done this evening.

I snap some pics too. Buzy weekend. So my applogies for not posting sooner.


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## 5boats-later (Aug 5, 2013)

Hey guys I'm new to tinboats! My boat sat on a trailer with rollers for three years and then I bought it from my uncle. He said that it would flat out haul butt. It's a 15' foot Sears with a 25 hp gamefisher! Yeah I know 25hp gamefisher but I think it was the only made for one year. Any way the boat has a hook in it from the rollers and will now hit WOT because of it. My question is what if I took the boat and rolled it over put pressure on top ( which would be the bottom) and use a 2x6 on top of a car jack and slowly put pressure on hook from inside of boat would that actually work on popping it out!


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## 5boats-later (Aug 6, 2013)

also here is a pic of the ok jon! Painting it now figured ill make a homemade skiff. My wife loves riding in the boat so I guess ill paint her up make her look some what pretty haha! Anyway let me know if y'all think a car jack would work. Looked this morning and the hook is in the middle of the boat very flexible! Thank again


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## surfman (Aug 6, 2013)

Holy cow of course it is plowing, not only do you have the motor mounted in the upper most trimmed position but, you also have a piece of plywood adding even more tilt to the motor. Notice that the transom has an angle to it. That piece of plywood has got to go all the way up or just go all together.

You are using the last hole, not the first, by the way. The first hole is all the way down.

It is okay to mount the engine a little high but, too high will cause the prop to ventilate, I would also try the second hole from the transom, after I got rid of that plywood.


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## Led_Junkie (Aug 6, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324946#p324946 said:


> surfman » 06 Aug 2013, 06:19[/url]"]Holy cow of course it is plowing, not only do you have the motor mounted in the upper most trimmed position but, you also have a piece of plywood adding even more tilt to the motor. Notice that the transom has an angle to it. That piece of plywood has got to go all the way up or just go all together.
> 
> You are using the last hole, not the first, by the way. The first hole is all the way down.
> 
> It is okay to mount the engine a little high but, too high will cause the prop to ventilate, I would also try the second hole from the transom, after I got rid of that plywood.



I'll try that too. I was just adding the plywood back the way it was. As one can see I don't know much about motorboats. 

I was using the 1st hole, although last outing I used the 2nd. The photo just shows the motor after being transported, I kick the motor back so it doesn't bounce on the ground when trailering. I need to cross several railroad crossings so I need some clearance. I tilt the motor back and move the pin up to clear the ground..

Once I added the plywood to the top of the transom, the degree of the transom is the same just being thicker, correct? no more so than if I use 3" angle to fabricate a jack plate. The offense was not bringing the plywood up all the way to the top, correct? Giving an uneven clamping position thus building in a degree of tilt that was condusive to the plowing. 

Thanks for the help I am just trying to figure this out. I didn't get to take pics last night. I'll post ASAP though.
Thanks everyone.


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## FerrisBueller (Aug 6, 2013)

Yes definitely post a pic of the bottom of the hull and check for a hook, otherwise you're just playing a guessing game. If there's a hook, then that is a major contributor to your problem. Otherwise it's just a matter of messing with the motor and the weight distribution.


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## WaterWaif (Aug 6, 2013)

Too, and you may have all ready gathered, In adjusting trim (angle) of motor in relation to transom,adjustment is based on top speed performance. I mean if plowing is the issue above 3/4 throttle,adjusting that out is goal. It is an interesting balance between bow rising at lower speed and it coming down at higher,with a surge wanting to poop transom on deceleration but that's trim! More time on your part and adjusting load and trim ,you,ll find the sweet spot. have fun with your craft!.


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## surfman (Aug 6, 2013)

Yes adding the plywood all the way up is necessary, if that plywood has to be there. You were adding a bunch of extra tilt. As mentioned before, lower the motor and I would start with the second hole and then go up from there. I have mine on the top hole and I have a home made bracket that sets the motor back about 5 inches. Mine is on a john boat though, not a V.


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## Led_Junkie (Aug 6, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=324987#p324987 said:


> WaterWaif » 06 Aug 2013, 11:10[/url]"]Too, and you may have all ready gathered, In adjusting trim (angle) of motor in relation to transom,adjustment is based on top speed performance. I mean if plowing is the issue above 3/4 throttle,adjusting that out is goal. It is an interesting balance between bow rising at lower speed and it coming down at higher,with a surge wanting to poop transom on deceleration but that's trim! More time on your part and adjusting load and trim ,you,ll find the sweet spot. have fun with your craft!.



I gotcha. I may never find nirvana, just a balance between ok and not so ok. I keep working on the balance deal everytime I go out. I'm moving my trolling motor to the front. That will help somewhat I needed to lengthen the wiring. I have really only have the gas tank (6gal), battery, tacklebox, poles, bait bucket, 2-12lb anchors one the bow, the other in the stern, Bucket of jugs, and my son and I, with an occational additional passenger. It is realitively full so I cannot imagine anything else.

I was planning on a casting deck forward level with the seats and using the space beneath as storage, but I dont know now. It may be too much weight forward. I see all these folks with the loaded decks with carpet on boats the same size, then think wow. Is that really stable? Or does the extra weight help balance?


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## 5boats-later (Aug 6, 2013)

So what y'all are saying is if there is a hook under boat messing with trim and lowering or lifting motor would not help top speed? My 15' has a slight hook but noticeable. Low end gets up and moving an then the boat lays down and cause the motor to want to turn. Motor sounds as if it is in a bind!


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## FerrisBueller (Aug 6, 2013)

Led_Junkie said:


> I see all these folks with the loaded decks with carpet on boats the same size, then think wow. Is that really stable? Or does the extra weight help balance?



It really depends on the set-up of the boat and how high the deck is. Yes, adding more weight can add to the stability, as long as the weight is in the right place. A deck build too high may just make it tippy.


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## 5boats-later (Aug 6, 2013)

Hey guys so I got the hook out of the boat and am gonna go run it tomorrow to see how she rides. With the hook in it the boat was touching the running board along side of the trailer and also touching the rollers down the middle. After getting the hook out the boat wouldn't even touch the runners so I had to drop the rollers down! Ill check back in with the outcome


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## WaterWaif (Aug 6, 2013)

Led Junkie, sounds like you,ve got a better idea of options. One boat i run is 14 ft 25 hp e-rude. i stand on occasion when running part throttle to see over bow seat( neat trick one legged guy) when solo,and hull will try to "gallop" at high speed if much wave action so throttle gets eased back till smooth riding.. With daughter on bow seat boat is perfect at top speed on calm water.(She has g.p.s.d top speed there.) Each boat/motor combo needs trimmed to itself to prove its ability,adding weight has to have an effect,per craft and location and load.Most my weight on stern end.(Fuel,batts, outboard,2nd trolling motor. Side console is diagonal and opposite batts for a bit of balance.,if you are running a tiller thats like two outboards on rear, leaving bow light.) Once your transom is similar in geometry to original it would seem you would get better response to adjustments.


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## Zum (Aug 6, 2013)

5boats-later ...
It's great that you managed to get the hook from your boat.
I bet more people would chime in on your progress if you started your own thread.
It's alittle confusing when theres more than one topic on a thread and people may want to see what you have done to get rid of the hook.


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## marshman (Aug 6, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325004#p325004 said:


> Led_Junkie » 06 Aug 2013, 12:33[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=324987#p324987 said:
> ...




i think i would focus on getting the boat to run right before id sink money in to it decking/converting it.... 

5boatslater...youre mixing things up on this post with a different boat...you should start a post dealing with your boat, and youll probably get better help...

hooks and bent/deformed/dented bottoms are detrimental to small low powered hulls...creates drag and will never perform right.... for a boat to paddle or troll or just putt putt around its fine...but to plane out and run around it really needs to have a good straight bottom...

think about driving an old car/truck down the highway with 4 bald tires and the alignment all out of wack, shaking and shimmying... yeah, you can drive it, but its just dumb....


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## 5boats-later (Aug 6, 2013)

Yeah new to this my apologies fellas! Good luck with your boat!!


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## Led_Junkie (Aug 12, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325050#p325050 said:


> WaterWaif » 06 Aug 2013, 17:07[/url]"]Led Junkie, sounds like you,ve got a better idea of options. One boat i run is 14 ft 25 hp e-rude. i stand on occasion when running part throttle to see over bow seat( neat trick one legged guy) when solo,and hull will try to "gallop" at high speed if much wave action so throttle gets eased back till smooth riding.. With daughter on bow seat boat is perfect at top speed on calm water.(She has g.p.s.d top speed there.) Each boat/motor combo needs trimmed to itself to prove its ability,adding weight has to have an effect,per craft and location and load.Most my weight on stern end.(Fuel,batts, outboard,2nd trolling motor. Side console is diagonal and opposite batts for a bit of balance.,if you are running a tiller thats like two outboards on rear, leaving bow light.) Once your transom is similar in geometry to original it would seem you would get better response to adjustments.



I appreciate the comments. It is a tiller steer so it is very stern heavy. I just purchased some wiring to move the battery forward and I may lengthen the gas line to move it forward as well.

I ran my hand underneath the stern end Saturday and felt a very noticable dent just before the turn up to the transome area. It seems like the boat was dropped pretty hard numerous times. The weekend was busy so nothing was done. I did manage to get it out and run it with the motor on the pin closest to the transom (1st?) and it made the bow ride real high until it planed. I moved my son forward to balance things but the plowing ensued until I backed off the throttle again. 

I really need to find time to take the motor off, and flip the boat and really get an idea on what/s going on. Besides I still have to strip the paint, being 2-toned really isn't a good look.

The reason I am moving up to the deck is because I have the plywoood in my garage, so it wouldn't be any more layout of funds unless I decide to carpet it.


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## Ranchero50 (Aug 12, 2013)

Take some pictures of the boat and post them up. Motor angle on the stern, bottom of the hull, layout of your stuff. This thread is 2 pages of confusion so far. 

Your outside stern wood should go to the top of the transom, you can just slide a spare piece in to test run it. Cavitation plate should be level with the bottom of the hull and parallel. 

Some pics will help troubleshoot the other obvious stuff.


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