Outboard jet question

[randolph49]

I recently got a 14 foot klamath jac boat, rebuilt the transom got a mini jacker jack plate and put my 25hp evinrude with a jet pump on it. It jumps on plane and everything looks good exept it when on plane it throws some water up over the back of the transom like the pump is dragging in the water a little. I have the front of the jet intake level with the bottom of the boat like it supposed to be but my question is because of the four inch set back the jack plate adds should I lift the motor up a couple more inches to account for that setback?

 

[user 6672]

It may be due to the 1 inch setback..

Might want to try a splash plate:

 

[lets fish salt]

like skiny water alot ,to get to some of my salt holes ! do they make a lower foot for jhonson outboards 25 horse ? have not seen any where im at "ocala fla" how much much i would like to know ? let fish salt

 

[randolph49]

yeah they make them, mine is a san leandro heres a site you can look at www.outboardjets.com they have a list of all the years and models and everything. As for the price im not sure probably around 500 or so from what i have seen for used ones. I bought this complete motor with pump for 450 cause the guy thought the motor was blown. Turns out it just needed the carb rebuilt not sure why he thought the motor was blown...

 

[randolph49]

Yeah I have seen those splash plates before i think ill try that. Its hard to look over the back of my boat when im driving down the river but i bet that is the problem. ill put one on and let you know how it turns out, thanks

 

[gotmuddy]

If you get everything set up just right it wont splash up, unless you change the weight in the boat(another passenger). I spent a few hours getting mine just right but still put a splash plate on.

 

[randolph49]

yeah i got most of the weight toward the front of the boat (battery, gas tank etc.) its a tiller so i sit at the back and it evens out pretty good i weigh about 225 , it jumps on plane like its nothin and runs at an acceptable speed it just splashes that water up. I didnt know what splash plates were used for, I thought they were to help funnel the water toward the intake to improve performance this was my first jet outboard project so ive got some things to learn i guess.

 

[user 6672]

I used to have a Alumacraft 1648 Jon with a 30 hp Jonson jet.. it took some messing around with setup but i got it to not spray and run like a demon. Once you get it setup rite look into the intake fin's, i used/use mine as curb feelers because they would nick rocks before the foot would and they keep you from cavitating during turning and sliding.. which personally.. i loved sliding that 1648 through 2" of water.. cause i could

The spray plate is for funneling more water into the pump, same as the side skirt's but it also cuts down on spray and keeps it from cavitating in chop on bigger water.

 

[randolph49]

i noticed those side skirts in your picture I have never seen that before. do you have to drill and tap holes to install them? Im definately going to put both on my motor. I really wanna trick this project out, my next step is sharpening the impellor and throwin some paint on the boat and motor cause they look rough. If I can figure it out ill post some pics of it when im done, it should be pretty sweet.

 

[Lil' Blue Rude]

The fins on the side of the shoe will probably slow you down some. Adds some more resistance. Some people have them welded on to the shoe.
Spray plate will stop the water from coming over the transom. I've got tilt trim on my motor and I haven't installed and sprray plate yet and if I'm n ot careful When I'm trimoning the motor I'll get water coming over the transom. Kinda depends on load speed and the amount of trim if the water comes over. Spray plates normally fix the problem though.
If you want to take the time to do it you can unbolt the pump and smooth out the ruff casting in the pump for some more performance.
Raise the motor just as high as you can get it without cavitating when you pin the throttle. It should be able to run it's fastest then.
Can't wait to see some pics.

 

[user 6672]

The intake fins have no impact on speed.. from my experience with the past 2 jets.

I got the image from here:

https://www.sschapterpsa.com/ramblings/outboard_jet_maintenance.htm

Good article..

 

[randolph49]

That is a good article thanks for puttin that on there, I didnt realize you could add that flush fitting to the pump. I have been taking mine to the river to run it and work on it, Im gonna add that too.

 

[gotmuddy]

great article, after reading that I have some more ideas to try to squeeze a couple more mph out of my rig.

 

[riverracer]

My advice is to get rid of that jackplate and to set ur motor up about 1/8 to 3/16, jackplates and jets dont work well together !

 

[randolph49]

Like I said Im not having problems with the performance or cavitation or anything the boat gets right up and goes and it runs as shallow as it gets, I jammed it through about two or three inches of water the other day testing it out. I have a few buddys that have jackplates with setbacks and they have never have any problems that i know of. I think Im gonna stick with the splash plate, intake fins and sharpening up the impeller I think that will do it for me, I dont need to race down the river like a demon around here with all the logs and stuff around here its better to slow down a little and take your time, The big stripers come out at night anyway :lol:

 

[Lil' Blue Rude]

If you don't have any problem with cavitation why are you putting intake fins on the shoe?

 

[randolph49]

I haven't had problems with cavitation in normal conditions but i have read up a little and they assist in funneling water to the intake and help during choppy water conditions, they are pretty cheap and easy to install so why not have the extra back up if I ever need it?

 

[Lil' Blue Rude]

Fair enough, let us now how it all turns out.

 

[gotmuddy]

My advice is to get rid of that jackplate and to set ur motor up about 1/8 to 3/16, jackplates and jets dont work well together !

I use my 9.9 on this boat so I need to keep the jackplate.