Starboard engine rpm cap while on water

[nughaifn]

My 243vrx starboard engine show check engine light with no fault code while in water and rpm wouldn’t exceed 4K. Port engine runs normal.

Once in trailer, starboard would rev normal to 7-8k rpm.

Not sure what could be the issue?

 

[Dean P]

Is there anything stuck in the grate or behind it? That "alleyway" must be free of any debris.

 

[Sccala]

My 243vrx starboard engine show check engine light with no fault code while in water and rpm wouldn’t exceed 4K. Port engine runs normal.

Once in trailer, starboard would rev normal to 7-8k rpm.

Not sure what could be the issue?

Did you ever figure out the problem? I have sane issue. Starboard engine won’t go past 6k. Port fine. I replaced spark plugs and 2 of the starboard cylinders had water in them, manifested by rusted spark plugs that also had water droplets on them upon removal. Not sure how water got it, or how to remediate, but I bet that’s the problem. I went for a test run after putting in new plugs…but problem persisted.

 

[JetBoat195G]

I'm not sure if your Yamaha has an intercooler, but if there is water in the cylinders, could it be that the intercooler is leaking? Just a thought. Here is a somewhat related thread.

https://jetboaters.net/threads/speedster-engine-surges.36290/