F225 surging nightmare

[swimdad]

I have twin 2003 F225's with 200 hours and I think one is possessed. It will run fine to 3800, you can baby it up to 4000-4100 but anymore else and it will drop to 3200 or so and surge back and forth. We have replaced EVERY filter had injectors rebuilt and certified, had the VST cleaned 3x, plugs replaced and most recently the main fuel pump replaced. We have tried pumping the bulb while running around the 4100 rpm cutoff and no difference. No codes are showing up on the yamaha software.

We are on mechanic #3, 2 of whom are Factory certified, and I have spent several thousand $ paying guys $100+ an hour to "try and figure out whats wrong" for several hours or days at a time with no results.

Any thoughts, ideas or name of a mechanic in the Galveston, Houston area who will guarantee their work would be much appreciated.

[boats.net]

Did the mechanics water test it and check it while it was surging? Did they run any test on engine when it was surging?

[Bull GT]

F225 nightmare

Have the same problem on a twin F225 boat with one engine not going above 3600, if it does go up to 4000 rpm then it falls back to 3400 and surges back and forth but will not go above 4000.

We have done all the things listed above including running the engine with the YDS connected to the computer, nothing shows up. I am really desperate solve the problem as we have already spent 16 man hours on it.

help please.

[Bull GT]

F225 nightmare

Did the mechanics water test it and check it while it was surging? Did they run any test on engine when it was surging?

Yes I did and it still did not show anything abnormal

[99yam40]

You are adding to an old post. It would be better to start you own post with all the proper information and history.
Sounds like you need to monitor the fuel pressure while problem is happening