# Jet drive ??"s



## BigTerp (Jan 15, 2013)

Need a little schooling on jet drives. My buddy just got a 1994 50/35 Johnson jet drive that needs a rebuild. He plans to do the work himself so we can use it on my boat (what a friend!!). I have a 1996 Tracker Sportsman 1648 flatbottom. Other than it's a short shaft, I don't know anything else about the motor other than the size and model year, he just picked it up the other day and I haven't had the chance to look it over. What things do I need to consider with the combination of this motor and my boat? Will it even work well on a 16' flatbottom? I'd like to stay away from any transom or other modifications. Any advice/tips/things to look out for, etc. are greatly appreciated!!!!


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## smackdaddy53 (Jan 15, 2013)

You will probably need a manual jack plate to raise the motor. The front of the jet foot needs to be close to flush with the bottom of the boat.


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## lowe1648 (Jan 15, 2013)

Depending on the height of your transom 15" or 20" a short shaft obj needs a 22" transom. I know with my Yamaha i would be able to bolt it onto a 20" and make it work without a transom riser. If you look at obj website they have all the info you need for setting it up


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## BigTerp (Jan 15, 2013)

Thanks for the quick replies. I have a 15" transom. I'll check out Johnson's website and see what knowledge I can gain.

So I'd probably have to gain 5-7 inches of transom height to make it work? Do jack plates provide that much?

What about motor weight? Any issues with it making me stern heavy?

How about performance with a flatbottom? I've read jet drives do better with tunnel hulls.


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## BigTerp (Jan 15, 2013)

lowe1648 said:


> Depending on the height of your transom 15" or 20" a short shaft obj needs a 22" transom. I know with my Yamaha i would be able to bolt it onto a 20" and make it work without a transom riser. If you look at obj website they have all the info you need for setting it up



I checked out Johnson's website, but couldn't find much. Maybe your referring to a different website?


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## shallowminedid (Jan 15, 2013)

60 40s are light so weight shouldnt be an issue. jack plates usually raise motor 6 inches up. and it https://www.outboardjets.com they do do better with tunnels but u dont need one a tunnel just lets u get in 2 inches of water without worryin about ur foot


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## Lil' Blue Rude (Jan 15, 2013)

You won't have to worry about weight I had the same motor on my 16' 42" flat bottom. Just swapped it for a 60/40 evinrude. It will do fine on a flat bottom. Biggest diffrence with the tunnel is you gain a little more clearance compared to a flat bottom. Youd gain more clearance from the tunnel if your boat was a semi v. Speed should be better with the flat bottom. Alot of people have these motors on 17' 52" around here so it'll push you fine. 
Good strong motor. I know I loved mine but I wanted to go faster so I moved on to bigger and better.


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## BigTerp (Jan 16, 2013)

Thanks for all the responses!!

After checking out OBJ and listening to you guys, it's definitely doable. Just going to depend on how much work is involved in getting the motor back in shape. 

Also throwing around options for tiller vs. stick steer. I'm planning on removing my middle bench and installing a pin mounted seat and extending the front deck just a bit. I use this boat alot for waterfowl hunting and am trying to keep an open floor plan for gear and easier/safer navigation throughout the boat with heavy waders on and freezing temperatures. So right now I'm leaning towards converting this thing to a tiller (if possible) to keep things nice and open, it's currently setup for controls.


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## shallowminedid (Jan 16, 2013)

something u may not know is if the jet foot is not set close to perfect it will also send a spray into the boat. not fun with tillers. or add a splash plate


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## BigTerp (Jan 16, 2013)

How exactly should the foot be set? From what I've read it sounds like the front of the foot should level with the bottom of the boat. Not sure about trim though.


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## shallowminedid (Jan 16, 2013)

the lowest part of my foot is level with my hull.mine is like an inch higher than most. my theory to setting the height... keep raising it till it slips. when i had the leading edge level i had spray goin 10 feet in the air from hitting the front of the jet pump and spraying straight up. most people add a splash plate from the hull to the foot to eliminate that. or a tunnel does too. and i think if ur jackplate has a set back that makes it worse


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## smackdaddy53 (Jan 16, 2013)

BigTerp said:


> How exactly should the foot be set? From what I've read it sounds like the front of the foot should level with the bottom of the boat. Not sure about trim though.


Read #6
https://www.outboardjets.com/catalog/ownersmanual/Owners%20Manual.pdf


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## BigTerp (Jan 17, 2013)

Thanks. That makes pretty good sense.

How do you guys feel about homemade jack plates?


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## cva34 (Jan 17, 2013)

smackdaddy53 said:


> BigTerp said:
> 
> 
> > How exactly should the foot be set? From what I've read it sounds like the front of the foot should level with the bottom of the boat. Not sure about trim though.
> ...


 Thanks Smack thats some of the best info I have seen...I do not own or do I plan to.Just don't need to run that shallow ...But knowledge always comes in handy...cva34


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## smackdaddy53 (Jan 17, 2013)

BigTerp said:


> Thanks. That makes pretty good sense.
> 
> How do you guys feel about homemade jack plates?


Im going to fabricate one out of 3/8"x3"x3" aluminum angle. I had a bobs manual jack plate i was going to pick up from a guy but he stood me up three times. $50 for a $200 JP but i guess it was too good to be true. Now i have to reverse a paypal payment.


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## cva34 (Jan 17, 2013)

smackdaddy53 said:


> BigTerp said:
> 
> 
> > Thanks. That makes pretty good sense.
> ...




Me feel fine about homemade! Just thought what about a old /broken Hyd one 'cause What most most manual are is a SS all thread bolt replaceing the Ram..Should be a easy mod. and maybe cheap.The other thought well ? how much set back can you stand? ..cva34


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## BigTerp (Jan 17, 2013)

smackdaddy53 said:


> BigTerp said:
> 
> 
> > Thanks. That makes pretty good sense.
> ...



I've been checking out some plans that uses 1/4" aluminum angle. I'm thinking of a manual model with as little setback as possible. What kind of angle are you guys using 6061 or 6063?


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## BigTerp (Jan 25, 2013)

After doing some more research I'm at a loss on what is the best way to fit this motor to my boat. Jack plate, or some sort of transom riser. Going to have to raise the motor 5-6" and I'm guessing the motor weighs roughly 200#. I replaced the transom wood this past september, so I know it's in good shape. Just concerned a jack plate will put more stress on my transom than a transom riser. But I like the thought of a manual jack plate for the ability to fine tune the motor height. Thoughts?


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## Lil' Blue Rude (Jan 25, 2013)

I'd go with a transom riser myself. But that's just me. You can always slot the mounting holes on the motors tilt trim bracket to make fine adjustments. Little bit of fine tuning can make a big diffrence in perfomance.


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## BigTerp (Jan 28, 2013)

Lil' Blue Rude said:


> I'd go with a transom riser myself. But that's just me. You can always slot the mounting holes on the motors tilt trim bracket to make fine adjustments. Little bit of fine tuning can make a big diffrence in perfomance.



Thanks. The fine tuning aspect is why I think a manual jack plate would be better. Plus I can re-power easier down the road. Probably going to end up going the jack plate route. Thanks for all the suggestions!!


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## lowe1648 (Jan 28, 2013)

Im with lil blue rude on going with a riser instead of jack plate. I've heard about more pros then cons. I have two sets of holes in my motor mount one slotted and one not. I set my foot as to how obj recommends. Drilled and bolted the slotted holes ran it the tried higher and lower. I ended up putting the shoe where obj recommends and drilled and bolted. Once you find the correct spot you don't need to move it. With a jack plate most everyone I've seen post anything has had to extend the bottom of the boat to the intake to keep a smooth water flow. I personally don't see any positive in using a manual jack plate. Jack plates will cause your transom to fail faster then a riser because of the setback. I had to redo and reinforce my transom on my lowe after 10 years with a riser.


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## BigTerp (Jan 28, 2013)

Thanks. IF I end up going with a jackplate I would try to keep the setback as small as possible. But I don't see it being any less than 4" or so. Which sounds like that can be enough to cause issues.

So how exactly do I go about making a 5-6" riser? I've seen a few aftermarket ones, but in the limited research I did, only found ones that go 2-4". Would prefer to make my own, if possible.


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## Lil' Blue Rude (Jan 28, 2013)

Heres one way to make it. 
https://www.jetdoctor.net/products/detail.php?productID=17


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## BigTerp (Feb 1, 2013)

Thanks for the link. My buddy and I have been pondering ways to do this and have found several homemade ones that others have made. Since the motor itself will be bolted through my existing transom, a riser would only need to be sufficient enough to support the upper "lip" of the motor, correct? The mounting holes on the motor shouldn't have to go through the riser at all. My buddy is a mechanical engineer by trade, and doesn't think a riser is going to be supporting much of the motor at all. Just trying to get a better idea of if we need to over engineer this, or just make a simple riser that will allow the motor to rest on it.


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## Lil' Blue Rude (Feb 1, 2013)

Here's a link of a boat that has a woodens riser. But it gives you a better idea how it's gonna go together. https://semo.craigslist.org/boa/3584419926.html


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## BigTerp (Feb 4, 2013)

HA, I like that wooden riser. Thanks, it does give me a better visual of how it needs to be done.

What kind of fuel economy can I expect with this motor? I currently have a 6 gallon tank that I planned on using. I will be running mostly short distances for fishing but will occasionally have a 10-15 or so mile run to get to some duck hunting spots. Should I consider a larger tank, or will 6 gallons be sufficient?


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## lowe1648 (Feb 4, 2013)

I would just bring another 6 gal tank with on your longer runs. I usually bring 14 gallons with for a weekend of camping.


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## BigTerp (Feb 4, 2013)

Thanks for all the help!!! I finally got my ideas together to get finished with my boat work. And then this jet threw a wrench into it, in a good way though. I'm sure I'll have a bunch more questions once I really get into the rebuild and get everything tied together. Hopefully I'll have everything ready to go come mid/late spring!!!


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## catmansteve (Feb 5, 2013)

Here's how I built the riser on my 14', it's just waterproof plywood and heavy aluminum angle with Emt conduit for bracing. The diagonal braces from the riser up to the gunwhales are pretty important, it's why you see the huge gussets on "jet sled" type boats
https://www.tinboats.net/forum/viewtopic.php?f=48&t=26356


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## BigTerp (Feb 6, 2013)

Thanks. You had to raise yours to 27"? I'm thinking I only need to go to 20 or 21". Need to do some measurements to be sure. But after seeing yours having to go up that high, I'm a bit more confident in doing my own.


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## catmansteve (Feb 6, 2013)

Yeah, 27", but my motor is a long shaft. Prop motors are 15" for "short shaft", 20" for long, but the rule of thumb is add 7" for the jet and fine tune from there. 21-22" should be a good starting point for you, but you'll most likely need to move it up or down to find what works best for your boat. Too high will cause cavitation, too low will create extra drag, splashback, and possibly increased chance of tagging one of them famous Potomac ledges haha


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## BigTerp (Feb 7, 2013)

I thought the rule of thumb was to get the front of the jet foot even with the bottom of the hull? Based on my measurements (transom from top to bottom is 16.5", motor from front of jet foot to top mounting surface is about 21"? this is where I'm getting that I'll need ~4" of transom elevation. Am I missing something?

Yeah, those widow makers hiding under the Potomacs surface have me a bit nervous now that I'll be able to go faster than walking pace!!


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## catmansteve (Feb 7, 2013)

You're on the right track, most boats I've seen have the leading edge of the foot level with or slightly higher than the bottom. Check out the "owner's manual" page on Outboard Jets' site if you haven't already, they show how to make an adjustable riser as well as good info on setup and maintenance.
https://www.outboardjets.com/index.php
All I can tell you is learn the stretch of river you run the best you can, know where the tricky spots are, and pay attention to where other guys with jets run. It's intimidating at first, but once you get the hang of it you'll be hooked, I know I'm never going back to a prop boat on the river again


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## BigTerp (Feb 8, 2013)

Thanks. Yeah, I've checked out outborad jets. Thats were I'm getting my setup ideas from. Not sure if you've run the Potomac from Williamsport up to dam 5, but that's where I'll do most of my fishing. It gets pretty sketchy, especially during the summer time. But I've gotten a pretty good idea of where to and not to go.


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## lowe1648 (Feb 8, 2013)

BigTerp said:


> Thanks. Yeah, I've checked out outborad jets. Thats were I'm getting my setup ideas from. Not sure if you've run the Potomac from Williamsport up to dam 5, but that's where I'll do most of my fishing. It gets pretty sketchy, especially during the summer time. But I've gotten a pretty good idea of where to and not to go.


If your like most of us you will still go where you know you shouldn't.


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## BigTerp (Feb 8, 2013)

No doubt!!

I need to find a control box for this thing. I'm planning on stick steering, so I have that part figured out, but don't know what I need for a control box. I need one just with choke, no trim. I've searched and found several used ones, but not sure exactly what I need. The new BRP ones look to only work for '96 and newer. Anyone point me in the right direction?


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## Lil' Blue Rude (Feb 8, 2013)

Your looking for controls with the red plug connector. 96 up have a diffrent connector then the 95 and older here's a link to the controls you need. https://www.ebay.com/itm/Johnson-Evinrude-OMC-outboard-motor-control-red-plug-up-to-1995-WITH-CABLES-/111009199323?pt=Boat_Parts_Accessories_Gear&hash=item19d8a9f4db&vxp=mtr

Most of the time a short shaft jets transom will be 22".


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## shallowminedid (Feb 8, 2013)

heres the riser outboard jet makes or sells or recommends i dunno its on their website so its gotta be ok... https://www.outboardjets.com/catalog/2010/Transom%20Bracket/TRANSOM%20BRACKET.pdf


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## BigTerp (Feb 9, 2013)

Is this what I'm looking for??


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## River Rider (Feb 11, 2013)

That looks to be the correct wire harness.


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## Lil' Blue Rude (Feb 11, 2013)

Yeah the plugs right but personally I'd get a newer set then that. Those are off of a 70's maybe early 80's model. Not a hundred percent sure they'd work for you.


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## BigTerp (Feb 12, 2013)

Lil' Blue Rude said:


> Yeah the plugs right but personally I'd get a newer set then that. Those are off of a 70's maybe early 80's model. Not a hundred percent sure they'd work for you.



Thanks!! They do look rather beat up as well. Now that I know what I'm looking for I've found a few sets of newer ones on Ebay for around $150. Much better shape as well. Probably hold off and pick up a set of those when the time is right.


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## BigTerp (Mar 12, 2013)

Just a quick update.

My buddy and I tore into the jet a few weeks ago. Everything looks really good. Will need a new water pump impeller and we will go ahead and replace the water pump along with it. One of the piston heads has a crack in it, which we knew prior to purchasing. What is weird is that one of the clyinders is bored out .20 but the other is not. I'm guessing someone [email protected]$$#% a rebuild previously? We are also guessing that this is what caused the piston failure? I would think having one cylinder .20 larger would cause come compression or balance issues. I've talked to a few motor guys who suggested this caused a head gasket failure allowing water in and the motor hydrolocked which cracked the piston. Makes sense I guess. 

Either way, everything else is in pretty darn good shape. No signs of overheating or excessive wear. The front right side of the leading edge of the jet foot is broken off. Just the corner piece, if that makes sense, doesn't go back to the itake grates. Will she run ok like this? Another questions I have is there is a slight bit of play with the drive shaft. I think I remember reading this is normal, but I'd like to confirm.

Power head goes to my buddies motor guy this weak for a cylinder boring. He is going to bore both out to .30 over. Then the rebuild can begin. I'll be sure to let you all know how it goes. 

Thanks again for all the help!!!


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## BigTerp (Jul 9, 2013)

So FINALLY got the pistons in last week and the powerhead is currently at the machinist. Hoping to have it back this week. My buddy travels almost weekly for work, so between that and waiting for the pistons to come in (which took forever) the motor is still waiting to be reassembled. I also still have alot to finish up on the boat. Was originally shooting for August 1st to have her back on the water, but September 1st might be more realistic.

New piston. Never seen pistons that looked so fancy and had emblems on them. Hopefully I won't be seeing them again!!


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## BigTerp (Jul 9, 2013)

Anything else I need to be checking out regarding my rebuild? Besides the obvious things that need replaced (water pump, gaskets, etc.)

Been checking out Chris Carsons reeds, and am considering getting a set. He offers sport, drag and racing reed sets. What would the difference be between the three and should I be looking at one over the other?


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## Lil' Blue Rude (Jul 9, 2013)

did you add extra clearance to the cylinder since wiseco's are forged? Forged pistons need more clearance then a cast piston because the forged piston expand more at operating temp. As far as the reeds go probably the sport reeds. Think they'll last longer and are more of a recreational use reed. but you can ask Chris. he's great to deal with and I'm sure he'll tell you just about anything you want to know about the reeds.


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## BigTerp (Jul 10, 2013)

My buddy is in charge of the rebuild. He's rebuilt many dirt bike engines in the past. I asked him about the cast vs. forged and he confirmed that the forged needs a bit more clearance. So I'd imagine he passed the info. on to the machinist. He also uses Wiseco pistons in his dirtbikes. The same machinist he uses for his dirt bikes is doing the jet powerhead, so I'm sure he knows what he is doing. The Wiseco pistons should also come with a sheet that states reccommended clearances.

I admit, I don't know much about engines. Been learning alot through this process though. It looks like forged pistons are stronger than cast, and not as brittle? What are the other pros and cons between the two? Not that I'd change anything at this point, just curious.

Thanks for the suggestion on the reeds. I'll try and get in touch with Chris to see what he thinks.


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## Lil' Blue Rude (Jul 10, 2013)

The forged pitons are normally a little lighter and stronger. Down side is they grow more then a cast piston at operating temp so they need more clearance meaning they have more slop in the bore until they are at operating temp. So you need to make sure the motors had enough time to warm up before taking off. Not to say you don't need to with cast pistons to but there's just more room for the forged pistons to rattle around in the cylinder then the cast pistons do when not at operating temp. At least that's what I've been told and read about. Kinda makes sense.


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## BigTerp (Jul 11, 2013)

Thanks Blue. I've read the same thing regarding the slop in the bore. I've heard some say they can make a sort of diesel engine noise until they get warmed up. Anxious to get the block back so we can finish up the rebuild!!!


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