2000 Seadoo GTS won’t rev and accelerate in water

[Hsutton28]

I’ve got an issue with my 2000 Seadoo GTS and I feel like I’ve hit a wall with diagnosis.

I took the jetski out for the first time this year a few weeks ago and ran it for over 3 hours with 0 issues. It would start perfect, it would rev perfect, it had plenty of power. After a full day of driving, it began to rev high for 3-4 seconds, then cut power for 3-4 seconds and repeat. After about 20 minutes of this it finally wouldn’t rev any higher than idle and eventually just died when I gave it throttle.

I took it home and replaced both fuel filters (someone long ago put an extra external filter on the inlet line), fully rebuilt the carb, and cleared all the fuel lines including the breather. I took the intake manifold off as well and checked the oil pump for any blockages.

After putting everything back together, it starts and it runs like a dream on the trailer. Once I get on water, the ski will not accelerate more than 3-4k RPMs. If I put the ski in neutral/reverse, every now and then it will hit redline but not often. After about 10 minutes or so of driving, if I shut the ski off, it struggles to start again and sometimes takes 30+ cranks to turn over.

I checked the voltage of the battery on the trailer when revving and it stayed between 12-14 volts all the way from idle to redline.

Any thoughts on what else the issue could be?

 

[mikidymac]

Check compression.

Continuing to try and run it for 20 minutes when it’s surging and starving for fuel usually ruins the engine. Running lean will kill a 2-stroke.

 

[Hsutton28]

Ran a compression test and both cylinders capped out at around 90psi. I fear the worst but I don’t understand how it could be that low and still start and run fine up to 4k RPMs? Even hitting redline with ease on the trailer

 

[tobytd]

Hopefully you have a harbor freight gauge… Seems they all read 90.
They usually run good on the trailer with no load.
Rent a gauge at the auto parts store, and check again.
Rebuild the fuel system! … if it’s not too late

 

[burtshaver2021]

As mentioned if they are both 90 pounds, good chance your harbour freight gauge is garbage. It’s well known that they are

 

[Hsutton28]

I tested the gauge on another jetski of mine and it also pinged 90psi on both cylinders, rented the gauge from Orileys so hopefully it’s just garbage. I’ll get another one from advance and try this afternoon. Thanks everyone, will update soon

 

[mikidymac]

It's almost like we have seen this Harbor Freight gauge fiasco before.....
It makes me wonder how many people have rebuilt good engines based on that junk.
I'm starting to think a Harbor Freight - SBT conspiracy is a brewn'.

 

[Hsutton28]

Update: I took an authentic OEM compression gauge and both cylinders topped out around 135-140psi so thankfully engine is not blown!

I took the carb off again and fully rebuilt the entire thing, removed the gas take and blew out every fuel line on the ski. Still no luck….

I have plenty of fuel pressure getting to the carb itself but to completely rule out this being a fuel issue, I went ahead and ordered a brand new carb.

Anyone have any thoughts on what it still could be if the new carb doesn’t fix the issue?

 

[burtshaver2021]

To rule out the carb, rebuild it with the back to OEM kit, re use the spring that’s in the carb now, check the sizes of your pilot and main jet to make sure they are the correct t ones, set your ilow and high screws to factory specs , if the lines are the grey tempo lines, change them to good black fuel lines like continental, not the cheap clear fuel lines off Amazon , not sure what engine you have but if it’s any engine but the 951 it’s 1/4” ID, replace the fuel selector valve and o ring in the fuel filter, remove any aftermarket inline fuel filters and follow mikidymacs carb rebuild thread, do all testing as per the the carb rebuild thread. That will rule out it being a fuel issue. If it’s a 787, might be a good idea to clean and inspect the rave valves as well.