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Discussion Starter #1
I just rebuilt the top end of my 90 sea-doo sp and took it out to test it in the water, but it had a major lack of momentum. I will not say lack of power because when I did a compression test on the ski itg had 130psi per cylinder. When I first give it throttle it seems like it is about to take off, but then it seems to die off with only enough momentum to move the ski, but barely lift the bow out of the water. Could this be caused by the fuel pump or the fuel filter, or both? Also while I had it in the water I took the seat off to see if I could see anything that might be wrong (which I didn't) and I did not notice any water flowing through any of the small clear lines. Should I be able to see water flowing through these lines? I did notice water in the 2 larger lines from the side of the hull near the front, under the storage compartment, but that was it. If any one has any help to offer it is greatly appreciated. Yhank you in advance.
 

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Discussion Starter #2
Ok, so I replaced the fuel pump, and checked the fuel and oil filters (both are as clean as new). But there is still a problem. When the ski is out of the water, with the flush system onit, it revs and sounds strong, but when it is in the waternothing, the ski barely moves in the water:mad: . Any ideas?
 

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Did you check your Rotary Valve when you did the rebuild? Sounds like it could be damaged, mis-adjusted, or the clearance could be too great ie. worn out.
 

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Reving out of water doesn't mean as much as you'd think since there's no load on the engine.

Why did you rebuild the topend?
 

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mhillis said:
Ok, so I replaced the fuel pump, and checked the fuel and oil filters (both are as clean as new). But there is still a problem. When the ski is out of the water, with the flush system onit, it revs and sounds strong, but when it is in the waternothing, the ski barely moves in the water:mad: . Any ideas?

OK, so I just noticed your second post...

Have you rebuilt the carb yet? If not, that's probably whats wrong.
 

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mhillis said:
Ok, so I replaced the fuel pump, and checked the fuel and oil filters (both are as clean as new). But there is still a problem. When the ski is out of the water, with the flush system onit, it revs and sounds strong, but when it is in the waternothing, the ski barely moves in the water:mad: . Any ideas?
do not rev the ski out of water more than 1/4 throttle, u will throw your pump out of wack and end up with a serious mess. this pumps need water going through them
 

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Discussion Starter #8
Knightofwyte I did not chack the rotary valve when I did the rebuild. I was told by the guy I bought the ski from that the carb had work don on it last year. How possible is it that the rotary valve is the prob? How can I determine TDC without a gague?
 

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An out of spec RV can cause the symptoms you're having, but it could also be a really poorly tuned carb... I was asking why you rebuilt the topend because that would help me know if there's any possible damage to the rotary valve.

And you can determine TDC the redneck way by using a pencil in the cylinder through the sparkplug whole. Rotate the crank until the pencil reaches it's apex, where it stops going up and before it starts coming down. That's TDC.
 

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Discussion Starter #10
I rebuilt the top end because the compression was too low, and the guy I bought the ski from was told (by a sea-doo mechanic) that the rings and pistons needed to be replaced. I took the cylinders to get honed and was told that they actualy needed to be bored. I had them bored to 76.5 because that was the only size pistons I had access to at the time. So I rebuilt the top end and here I am now.
 
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