# looking at a jet convesion



## JoshKeller (Jan 10, 2014)

hi guys, i have a riveted 1648 alumacraft mv. powered by a 2001 johnson 35 hp 3 cylinder outboard. boat weight is approx 600 lbs with batteries, trolling motor, motor. I have found some jet lowers for my motor, and am wondering if it will plane/push my boat well. going by 30% powerloss, it turns my 35 into a 24.5 hp jet. I did have a 25 hp merc prop on the boat before and it ran 28 mph with two people. i will be keeping my prop lower for the majority of my fishing, but would really love to have the jet option for certain areas of the potomac. thanks guys.


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## Lil' Blue Rude (Jan 11, 2014)

Won't be a speed demon but it should get you up and down the river. I've known of people running the 25hp 2 cylinder omc on boats that size and some even bigger.


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## dhoganjr (Jan 11, 2014)

+1
It will get you where you need to go. Should plane out and run fine.

Keep in mind, if you haven't run jets before, that the jet is going to need to be mounted higher. So if you're going to swap back and forth you will probably need a jack plate to make it easier to adjust the height.

Good luck and have fun with it!!!


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## JoshKeller (Jan 11, 2014)

my motor uses the same mid section for the 15 and 20" models, they just use a 5" extension. my plan was to order the short shaft jet pump and remove the extension, and when wanting to go back to prop, just adding the 5" extension back in.


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## JL8Jeff (Jan 16, 2014)

I was thinking about doing the same thing with my 40 hp Evinrude but ended up finding a Mercury 60/45 jet with the short shaft for cheaper than the conversion. I have yet to mount it up on the boat though, everything is packed away for the winter for now. If the jet works out well, I can sell the 40 hp prop and reduce my cost. But my 40 seems to run really well so i might just keep it if I ever need it for another boat.


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## JoshKeller (Jan 16, 2014)

yeah, i thought about buying a jet already made, but the pump brand new is $1700. i can remove the lower unit on my motor in under 5 minutes.


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## JoshKeller (Jan 17, 2014)

i'm looking at the chart on outboardjets.com and it says powerhead horsepower - is this the old crankshaft hp rating, or the newer at the prop measurement? from what im hearing my 35 is actually closer to 40 hp at the prop, and around 45hp at the crank, which puts my boat weight well within the chart for its weight assuming 30% powerloss for the jet conversion.


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## Ranchero50 (Jan 18, 2014)

I'd just call them and bend their ear for a bit with what you actually have and how it's loaded to see what they suggest.


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## JoshKeller (Jan 18, 2014)

yeah, i called, he said it would push it, but didnt have much more information than that, since my motor is pretty rare. does anyone with a short shaft jet happen to have the measurement from the area where the jet pump mounts to the motors mid section, to the foot of the jet where it needs to be flush with the bottom of the hull? would like to check my measurements and make sure i dont need to redrill some holes in my static transom riser. 

right now i have it set so that my 20" prop motors cavitation plate is dead even with the bottom of the hull, with one bolt hole available to lower the motor, and 2 more to raise it.


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## mphelle (Jan 19, 2014)

That motor had a short production run, did the people at OBJ tell you what size pump/impeller it was fitted with? Need to know which one to measure.


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## JL8Jeff (Jan 19, 2014)

My short shaft 60/45 Mercury measures around 9-3/4" from the front of the jet foot to where it bolts to the midsection and the rear measures around 11". The foot is angled so it's higher in the front to allow the water in.


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## JoshKeller (Jan 19, 2014)

he told me it was model AM. 

just measured my motor, and with the motor all the way down, it is 9" from the midsection of the motor, to the bottom of the boat. 

the center of my boat has a chine and the drain plug. will this be a problem? just mount the motor so the front of the intake is in line with the lowest point of the hull?


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## mphelle (Jan 19, 2014)

Looks like it uses the same medium pump and 5 7/8 impeller as the model Q which is used on the J/E 20-35hp. I have a 83 Johnson 35 jet over at my shop, I'll get you a measurement later tonight.


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## dhoganjr (Jan 19, 2014)

I've never mounted one on a mod-v but I would put a straight edge beside the chine. Board, ruler, or whatever you have handy. Mount the leading edge of the jet foot at that height. Will be trial and error from there, might be able to go up about a 1/4" or so. May have to come down a bit, depends on if you get cavitation from the chine being lower. If it is too low the foot is going to drag in the water slowing you down.

Hope this helps.


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## mphelle (Jan 19, 2014)

1983 Johnson 35 jet


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## JoshKeller (Jan 19, 2014)

spent an hour today at the river and deserted ramp messing with motor height on my prop. it runs best there its currently at, and i just went and measured - 8.5" would put the front edge of the intake approx 1/16" below the bottom on the hull.


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## dhoganjr (Jan 19, 2014)

Since it is that close, put the pump on and see how it performs. You can adjust from there if you need too. Once you get the pump on, you'll be able to get exact measurements. Since you have 2 holes higher to go, raising it one might put it right where you need it.


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## JoshKeller (Jan 19, 2014)

so it will certainly work with the setup i have? height tweaking may be required, but it will work? since the bottom hole of my motor bracket is a slot instead of individual holes, i have no objections so drilling another hole in the extension bracket for one of the top 4 bolt holes to line up if i need to infinitely be able to adjust the height. 



[url=https://tinboats.net/forum/viewtopic.php?p=339126#p339126 said:


> dhoganjr » 1 minute ago[/url]"]Since it is that close, put the pump on and see how it performs. You can adjust from there if you need too. Once you get the pump on, you'll be able to get exact measurements. Since you have 2 holes higher to go, raising it one might put it right where you need it.


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## dhoganjr (Jan 20, 2014)

It should work, I've only dealt with flat bottoms, but they have a strake in the center to. Some are built without them and some people remove a couple of feet, but they run fine with them. Once you get it mounted and run it, you can fine tune it from there.


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## JoshKeller (Jan 20, 2014)

Excellent. Most say it works. A few say it won't. Called outboard jets to figure out exactly how much it will cost, and the girl swore up and down it wouldn't plane, even though another guy from there said it'd be fine. If it planed out easily with a 25 prop, does that mean it'd run approximately the same speed and plane as easily if it was 25 HP at the jet pump?


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## Ranchero50 (Jan 20, 2014)

Maybe, it's hard to say how your engine will like the pump and how the pump will like the hull. It's all about getting the pressurized water out the nozzle.


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## Lil' Blue Rude (Jan 20, 2014)

Honestly don't think the people at outboard jet really know everything about how there pumps perform on a actual boat. I've tried calling and talking to them about getting some more performance out of my setup and what I've done and what gains I've seen and the first thing they tell me is take out the stainless impeller because its slowing you down. I've gained at least 1mph on every boat I've ever run a stainless in. I'm talking back to back runs brand new impellers. I couldn't convince them of that. Not saying they don't know anything about them because I'm sure they got a pretty good idea on general performance but I don't know that I'd take there word as the gossypol.


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## JoshKeller (Jan 20, 2014)

at this point im wondering if its worth the $1700 risk. my boat is pushing 700 lbs with two batteries, 24v trolling motor, and decking. may just fish this year with the prop and look for a 50/35 jet, or a welded jet package already put together.

staring at the chart on outboard jets, it looks like 35hp would be 1050 or so pounds, not 900. is anyone else seeing this? ive been told the 3 cylinder 35 is closer to a 40 than a 35, but i just dont want to be stuck with a $1700 jet pump that wont move my boat. this is really something i wish i could test out and send back if it doesnt work. 

I did have a 1970 omc 25 hp 2 cylinder on this boat for a few weeks, and it even planed it out fine. that was a crankshaft measured 25, vs the prop shaft 35 i have now. it would do about 25 mph. if i got too much weight in the back, i just had my passenger move to the front and it immediately planed out.


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## Ranchero50 (Jan 21, 2014)

Call this guy up and ask him how his performed...

https://winchester.craigslist.org/boa/4221479327.html

For your hull I'd get rid of the 3/4" plywood and go aluminum if you go for the jet conversion (heck I'd do it anyways). I'd also just keep my eyes open for jet boats for sale and buy a used one before selling your hull. 

This is about the worst time of year to go boat shopping. How much do you have in your setup now?


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## JoshKeller (Jan 21, 2014)

i paid 1900 for the new hull.. motor was free, trolling motor, two side finders was about 3 grand, but they'd transfer to a new boat. i believe ill look for a 50/35, or just buy a welded jet in a year or two and keep my riveted so i have options. i fish stonewall jackson every year, and the prop is nice to have up there for when it gets rough. 

im completely happy with how it runs with a prop, what would be the benefit to removing the 3/8" plywood and replacing it with $300 of aluminum?


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## Ranchero50 (Jan 21, 2014)

Benefit is probably around 1" of draft and it'll plane out easier without the extra weight. At the side my hull drafts 1.5", yeah, two knuckles deep. It's around 4" in the center. I've anchored at spots where my mushroom anchor isn't completely under water.

Perhaps you should just put a rock guard on your motor and work you way up through the nasties at idle? I've seen a bunch of small jon's idle up past the quarry. I've also seen full bore jet hulls belly in on the ridge lines (ugly)...

There's several miles of water from the islands down and most prop guys only see 2 of it.


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## JoshKeller (Jan 21, 2014)

yeah, ive had the boat the whole way up to the dam. run up to the ledge before the bend where the sand bar is.. trim up and idle through, or get out and pull, then go to the spring, and pull the boat through that riffle and idle up past the rail road trusses. can pretty much idle the whole way past the little conococheague and up to the dam.

right now my boat drafts about 5 -6" total. id like to put in a lighter floor all around, but im not sure i'd have the tools to cut the metal or anything precisely.

i mostly fish williamsport area in the spring and run up the conococheague to catch the big spawning largemouths right below the 63 bridge. id like to fish the paw paw/bonds landing area early in the spring, and if the water is up, im sure i can idle my way through. 

the majority of the year i fish shepherdstown since its 3 miles from my house, and i know that area of the river well enough that i run wot the whole way up past snyders, and early in the year, i've taken it the whole way to dam 4.


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## JL8Jeff (Jan 22, 2014)

I just saw a Johnson 50/35 pop up for sale around here on Craigslist. I forget if it was a short shaft or a long shaft though.


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## Tbradley (Jan 22, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=339196#p339196 said:


> JoshKeller » 20 Jan 2014, 17:45[/url]"]Excellent. Most say it works. A few say it won't. Called outboard jets to figure out exactly how much it will cost, and the girl swore up and down it wouldn't plane, even though another guy from there said it'd be fine. If it planed out easily with a 25 prop, does that mean it'd run approximately the same speed and plane as easily if it was 25 HP at the jet pump?


 
I HEAR YA... I called outboard jets numerous times and everytime I talked to that lady (not sure of the name) I got the same response you did, this won't plane that won't plane etc... The guy you need to talk to name is Brian. He was the most helpful. He spent a good amount of time on the phone answering all my questions. The lady wasn't much help.


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## JoshKeller (Jan 22, 2014)

I pretty much decided I'm going to just get another boat next spring and not give outboard jets my money directly. The lady telling me "its you're money, waste it if you want" was enough to sour me on the company


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## Canoeman (Jan 22, 2014)

I would say she was actually giving you good advice.. and i agree with her. She was trying to save you money by telling you the truth, regardless of how she said it or worded it or how you took it.. a 25/18 would not be enough to even plane that rig let alone you adding gear etc. You'd be blowing $1700 on the foot then youd have to try to sell it for a loss..

As said above.. Brian is the man.. ive been emailing him and doing business directly with OBJ for years now and have zero complaints.

Good choice on getting what you want instead of trying to make what you got "get by".


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## JoshKeller (Jan 22, 2014)

[url=https://tinboats.net/forum/viewtopic.php?p=339385#p339385 said:


> Canoeman » Today, 14:16[/url]"]I would say she was actually giving you good advice.. and i agree with her. She was trying to save you money by telling you the truth, regardless of how she said it or worded it or how you took it.. a 25/18 would not be enough to even plane that rig let alone you adding gear etc. You'd be blowing $1700 on the foot then youd have to try to sell it for a loss..
> 
> As said above.. Brian is the man.. ive been emailing him and doing business directly with OBJ for years now and have zero complaints.
> 
> Good choice on getting what you want instead of trying to make what you got "get by".




yeah, i agree, but the way the lady just kept on saying it even though i was not even talking about it anymore just kind of gave me the impression she was a bitch lol. and it wasnt for a 25/18 hp, it was a 35/25


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## smackdaddy53 (Jan 24, 2014)

For $1700 you could find a good used outboard jet and motor.


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## JoshKeller (Jan 24, 2014)

[url=https://tinboats.net/forum/viewtopic.php?p=339605#p339605 said:


> smackdaddy53 » 50 minutes ago[/url]"]For $1700 you could find a good used outboard jet and motor.




maybe in texas, but not in this part of the world - they are bought up as soon as they are put for sale if they are in good condition. ive talked to a few dealers about getting a 40/30 or a 50/35, and they actually recommended me putting the jet pump on my motor if its just a few times a year and i was really just interested in planing out. they said my two stroke was putting out a few more hp than 35 (likely around 38), and will be very close, if not a tiny bit better, than a 40/30 4 stroke. 

an employee at mare told me that since my boat is only rated for a 35, he has no doubt i'd plane out with the 35/25 conversion - also told me not to let that motor go, because its a sweetheart and i wont see another one.


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## smackdaddy53 (Jan 24, 2014)

If I dont like how my 60/45 performs It may be on the market so I can get a 115


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## rockdamage (Jan 24, 2014)

I've ran those engines with obj on them...... weak ! 
save your money


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## JoshKeller (Jan 26, 2014)

i know this has been beat to death, but what are your thoughts on this chart? the 4 stroke yamaha 40/30 pushes this 800 lb bare hull/1500 lb package to 27 mph. wouldnt my 35 3 cylinder push a 700 lb loaded boat similar? my biggest concern in this investment is being able to get on plane. if its slow, i can deal with that, as long as i can run shallower than with my prop. if its 20 mph but stays on plane, im okay with that. this is simply for a once in a while fishing areas, 90% of the time i will be running my prop set up. 

https://www.yamahaoutboards.com/sites/default/files/bulletins/bulletin_4stroke_midthrustjetport_jet-drive_g3b_1656ccjdlx_f40jea_2011-06-13_alm.pdf


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## Ranchero50 (Jan 26, 2014)

Looking at the chart, 10+ seconds to hit 20 mph means you are going to be digging holes for a long time trying to get the hull to climb the hill of water so it'll plane out. I also seriously doubt you 2 stroke has the same power curve as the 4 stroke so that chart's value is dubious.

For skinny water you want a power plant that can pop the hull out of the water very quickly without digging a hole, then you throttle it back to around 3/4 so you have some reserve maneuvering power and you're not pushing the engine too hard (nor the fuel consumption).


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## JoshKeller (Jan 26, 2014)

looks like i have really no other option than to buy a second boat. giving up the prop isnt an option, and im limited to 35 hp with a prop.


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## JoshKeller (May 15, 2014)

to update, i found a 50/35 and bought it this evening. Now i just need to figure out if i want to fix up the boat it came with (1648 fisher markv2 set up open floor plan) or put the motor on my alumacraft and sell the boat.....


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## Jeeper (May 15, 2014)

It's ultimately up to you but there are several guys around me that run a 40 hp mercury jet on there alumacraft mv with no problems


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## JoshKeller (May 15, 2014)

i love the open floor of this new boat, would like to set it up stick steer. 

i also like the decking and the way i have my alumacraft rigged up. i would have to raise the transom 5 inches for the alumacraft. may just have two boats now - one for prop areas and one for jet. one things for sure, the bottom of this fisher is dinged up, i wouldnt cringe everytime i scraped or bumped something like i do the alumacraft.


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## dhoganjr (May 16, 2014)

Glad to hear you finally found one. If you can afford it and have the room, I'd keep both. Best of both worlds, like you said the boat is already beat up so you'll be able to get even farther in the shallows and to fishing spots others paddle to. Use the prop for the lakes for longer runs and heavy chop. 

If nothing else keep the Fisher long enough to learn how to run a jet and learn how shallow it will run and what they are capable of. If you haven't run or dealt with jets much it is best to start off with a beat up hull anyway. If you hit something, no big loss. 

Keep us updated, have fun with it.


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## JoshKeller (May 16, 2014)

Anyone know what gauge aluminum the old fishers are made of? Its a marsh hawk v2


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