OX66 engine problems

[73sidewinder]

Hello, I have been having alot of problems with my 2001, yamaha 225 OX66 this year. It started out cutting out at high RPM and I checked this forum and followed all the suggestions. So far I have replaced all of the fuel filters including the VST filter on the electric fuel pump, And I have removed and cleaned the fuel injector filters.

Now the engine is skipping, feels like the ignition is not working correctly. The engine skips in all RPM ranges but never cuts off. I could only get the RPM to max out at 4700 normally I get 5300 at WOT. As soon as I turn the key on the fuel pressure goes to 38 psi. When I increase the engine rpm to 2000 the fuel pressure increases to 40 and the needle bounces slightly. Pressure regulator checks out good also.

The voltage on the pump reads 9.5 volts at idle but increase to 14 volts when I increase the engine rpm to 2000. (Is this normal?)
RPM surges from 1800 to 2200 when I set it to 2000.

I also changed the spark plugs just in case but this did not fix it.

 

[cousinabe]

Re: OX66 engine problems

have you checked the orange spark plug caps are in spec?

 

[73sidewinder]

Re: OX66 engine problems

No

I have'nt checked the spark plug caps because the engine ran perfect last weekend for two hours but this weekend and two weeks ago it had the same problem. Yesterday when I first put the boat in the water it ran perfect for about ten minutes then the problem started. I keep thinking it is fuel related. I did have a real hard time putting the low pressure fuel filter back on so I am wondering if I might being sucking in air to the VST.

I have not cleaned the pressure regulator screen since I tested it with a vacuum pump, and it did lower the fuel pressure.