Seadoo XP runs great out of water

[Travlash]

I have a 96 XP 787. I just bought it. It runs great out of water. But when in water it won’t go over 5 mph or it will shut off. The only way to get it to run decent for a couple seconds is priming gas right into the carbs.

so far i have replaced the rectifier. I rebuilt the carbs. I also replaced the rotary valve I checked all the gas lines and nothing is plugged. Replaced the plugs and cut back the wires. Cleaned the grounds. The previous owner made this motor a pre mix so i don’t have an oil tank. They also set it up to run without a reserve. So i don’t believe there is a fuel selector.

like i said it runs great out of water but once there is a load on it. It doesn’t want to run.

two things to note:
I have not cleaned the rave valves.
the high adjuster on the carbs is seized and can not be adjusted.

 

[Tyman2020]

if im thinking correctly you ave to keep the oil tank in to lube the rotary valve assembly this is where people screw stuff up. Do a compression test. Should be 150 in each cylinder the farther from that you are the more chance the ski wont run in the water.

 

[Tyman2020]

Also did you use genuine mikuni carbs rebuild kits?

 

[Travlash]

Yes i did. I know about the oil to the rotary valve. I’m going to hook one up. Compression is 150-155 in both. I just lived up the valve for 5 min test run with oil on the valve

 

[Tyman2020]

Hmm compression sounds good...Did you leak test these carbs after the rebuild

 

[Travlash]

Hmm compression sounds good...Did you leak test these carbs after the rebuild

no i don’t know how to do that. But i had a buddy to a pop off pressure test and it’s 31. Can i put 717 gtx carbs on it and test them to see how it runs? My buddy has a pair.

 

[dr00andrew]

check out the parts of your drivetrain as well. you could have a bad wear ring or possibly the neoprene seal between the pump and the hull is worn out. also, what do you mean by a new rotary valve? did you replace the thin metal plate or did you put a new cover? the clearance between the rotary valve cover and valve needs to be within a certain spec, otherwise it will run good out of the water and poorly in the water.

also how long has this ski been running without oil hooked up to the rotary valves? im not sure why the po removed the oil tank because the instructions in a block off kit clearly state oil needs to go there.

 

[mikidymac]

No you can’t use the 720 carbs.

 

[Travlash]

check out the parts of your drivetrain as well. you could have a bad wear ring or possibly the neoprene seal between the pump and the hull is worn out. also, what do you mean by a new rotary valve? did you replace the thin metal plate or did you put a new cover? the clearance between the rotary valve cover and valve needs to be within a certain spec, otherwise it will run good out of the water and poorly in the water.

also how long has this ski been running without oil hooked up to the rotary valves? im not sure why the po removed the oil tank because the instructions in a block off kit clearly state oil needs to go there.

Question. Would it be that the high adjustments on the carbs are seized and causing it to bog out when i try to accelerate in the water ?

 

[dr00andrew]

Question. Would it be that the high adjustments on the carbs are seized and causing it to bog out when i try to accelerate in the water ?

what do you mean by seized? as in you can't turn your high speed adjuster in or out anymore? if you cant adjust your high speed screw, it is certainly possible. it would also depend on where the screw is stuck as well. knowing how many turns open/closed it is would help. if your ski is running good from idle- 1/3 throttle and only bogs when you try to really get on the gas, than you could point to the high speed adjuster being off. if you give it throttle and it bogs, that can mean you have too much fuel in your air/fuel mixter.

typically on carbureted engines in general, your high speed jet or "main"is affected in the range from 1/2 throttle to WOT, so unless you are in that throttle range and its giving you problems, im not sure you can say its your high speed adjuster or jet for that matter. when it comes to tuning a carburetor, you have to get a feel for where exactly in the throttle range your problem is happening. in the case of a seadoo, your closed throttle to 1/4 position is affected by your pop-off pressure, low speed adjuster and pilot jet and then your 1/3-WOT is all in your high speed adjuster and main jet. take it for a ride and dont give it more than 1/3 throttle and see how it runs.

better yet, why don't you check out this thread on tuning a carburetor for your ski. im not quite as experienced with tuning pwc carbs as i am with others, but it is generally the same concept. Carburetor Adjustments read through it and see what you can come up with

 

[Travlash]

Thank you for your response. I’m not able to accelerate passed 1/3 throttle without it shutting down. The adjustments are seized up that i literally can not spin both of them. And i have no idea how many turns they are seized at. Pop off pressure is good and the leak test was done yesterday. Both went well. Would you recommend getting used carbs and just replacing them? Would that have a chance at fixing the issue.

another thing I’d like to note, i have the fire arrested on. But don’t have the bolts for it. So for now i just zip tied that fire arrestor on and i can’t put the big black box over it Because i don’t have the right bolts. What type of affect would this have on the motor,since the intake box isn’t exactly on, but the fire arrestor is

 

[dr00andrew]

Thank you for your response. I’m not able to accelerate passed 1/3 throttle without it shutting down. The adjustments are seized up that i literally can not spin both of them. And i have no idea how many turns they are seized at. Pop off pressure is good and the leak test was done yesterday. Both went well. Would you recommend getting used carbs and just replacing them? Would that have a chance at fixing the issue.

another thing I’d like to note, i have the fire arrested on. But don’t have the bolts for it. So for now i just zip tied that fire arrestor on and i can’t put the big black box over it Because i don’t have the right bolts. What type of affect would this have on the motor,since the intake box isn’t exactly on, but the fire arrestor is

you definitely need to be able to adjust your carburetor, so you gotta do something about that. take them out and start macing your adjusters with wd-40 or some other kind of penetrating oil to try to break those threads loose. if you absolutely cant remove them, than i would look into buying a used set of carbs. at least then you can take your new carb parts and replace them with what you bought.

again check out your drive train as well, you may not be getting proper thrust in the water. with out any video evidence of what's going on, it can be hard to tell exactly what it is.

i am not too experienced with seadoos as i recently purchased one as well. there are definitely lots of other people who are much more knowledgable than me that could help you out. based on the info you are giving me, i would definitely say you need to get those high speed adjusters to the factory recommended spec for starters. any time you are tuning carburetors, go to the factory specs and work your way from there. i cant answer your intake box question accurately as i am unsure. my guess is that, they are put there for a reason and need to be on. water could potentially find its way into your engine if nothing is covering your flame arrestor. definitely look into your drive train, something as simple as a wear ring or a bad seal between the pump and the hull could cause your ski to run bad

 

[Travlash]

Thank you. I’ll post once i figure some more info out. How hard is it to find is it to find and replace the seal between the pump and hull. The wear ring is great.

 

[dr00andrew]

its very easy, just pull the 4 bolts that hold the pump housing to the hull and you should see it as soon as you remove it

https://lh3.googleusercontent.com/p...vziE2CRdaiudfB5NqEQOjaAiaCWXs2vAivjzhFg1zxrrO

 

[Travlash]

That seal is fine and the wear ring