Running out of Ideas.....

[LargeJohn]

I've been chasing an issue with a "new to me" 2008 GTI 155 SE. Idles and runs fine on trailer, but will not idle in water and tops out around 3800 rpm.

So far,

1. New plugs
2. Replace and calibrated TPS (due to trouble code)
3. New injectors
4. New coil packs. Verified strong fire in all cylinders
5. Tested/verified fuel pressure
6. Replaced fuel filters
7. Inspected and lubed throttle body
8. Replaced broken clamp on exhaust
9. Checked compression--125-130 on all cylinders
10. Removed and inspected airbox for obstructions
11. Checked fuses and power connections including grounds
12. Waiting for Idle Bypass Valve--no code but cannot feel/hear the motor run when powered
13. Ohm/volt tested sensors

Currently, no codes are present. No warnings displayed.

Where should I look next?

a. Can a fuel pump partially fail under load?
b. Intake Manifold leak?

[Shark]

How’s your pump look? How many hours? Ever been rebuilt?

[Drewski1126]

Fresh gas. ?

[LargeJohn]

How’s your pump look? How many hours? Ever been rebuilt?

106 hours. I don't have much history on this thing. I'm pretty sure that it has sat for the past 2-3 years.

I haven't touched the pump, but the wear ring and impeller look ok.

Could/would the pump limit rpm?

[LargeJohn]

Fresh gas. ?

Forgot to mention. Emptied out about 2 gallons of cloudy gas, and added 6 gallons of 91.

[Drewski1126]

Does it hit the reve limiter pretty easy on the trailer when you hit the throttle real quick.

You could check the pump bearing to make sure it isn’t goin out but I don’t think that would be it. There Probly be lots of vibrations if it was.

[711jrp]

J pipe leaking filling the hull up with exhaust? try running it without the seat on.

[LargeJohn]

Does it hit the reve limiter pretty easy on the trailer when you hit the throttle real quick.

You could check the pump bearing to make sure it isn’t goin out but I don’t think that would be it. There Probly be lots of vibrations if it was.

This is my first jet ski, so I'm not completely confident about normal operation and normal sounds, but I haven't noticed any bearing noises or excessive vibration.

Not sure that I understand the rev limiter.... On the trailer, it seems to hit 5500-6000 rpm pretty easily, but I've been reluctant to push it too hard for too long out of water.

I've seen some others mention replacing valves. The lack of power and being parked for a couple of years is pushing me that direction also...

[LargeJohn]

J pipe leaking filling the hull up with exhaust? try running it without the seat on.

I'll take another look at the exhaust and J pipe. When I replaced the main exhaust clamp, I thought it was the culprit, but not so.

[Drewski1126]

The 08 155 should have the updated valves if I’m not correct. They stopped putting the sodium filled valves in 07 I believe. Unless it’s not the original engine.
You can check the top edge of the valve and see what they are. Just pop off the valve cover and look at them
Good valve -75
Bad-72

Some where in the printing you’ll see those combinations.

Also make sure you got all that gas out. It will kill performance if there’s any old gas left in there.