Yamaha ox66 200 Saltwater series question.

First of all thanks in advance for any help here.

Engine runs smooth but I do not think it is getting to full RPM. What should full RPM be on a 22ft bay boat?

Second issue when motor is trimmed down any it cuts out when throttle is applied. If motor is not trimmed down it does not cut out runs smooth. However it will cavitate so I need it trimmed down some.


So for example I try to take off to get on plane with it trimmed down the engine cuts out like you turned the key off. RPMs up down up down like your turning key on and off.


With it trimmed level it will not cut out. Does not make any since to me but I am a hydraulic mechanic and certified large diesel engine mechanic. 2 strokes are not my thang. I know how they work but not enough to start troubleshooting this particular issue.

Any help would be greatly appreciated I just need a direction to start.

Might check out the 02 sensor. It gets carboned up and causes lots of weird things.

Thanks Catfish

I did all the service I could think of today.

The O2 was completely clogged hopefully that was my problem.


Primary fuel filter no good too. VST fuel filter screen was pretty dirty too.


Spark plug gaps where off by around .005 inches.


Changing out fuel seperator tomorrow.


It has to run better lol. We will see tomorrow.


I bet the trim issue is still there. Will update tomorrow night if any one gives a [censored] lol.

Yamaha website says that engine should run between 4500-5500 rpm. Im only getting 4000

Have you tried a different prop? Or did it run correctly before?

Update
After servicing everything the boat runs great now.
4800 rpms @ 45mph
No more stalling when trimmed down
I believe that O2 sensor was the culprit

My yamaha mechanic has always told me to prop out my engine so that it tops out at the maximum published RPM. If Yamaha says it should be 4500 - 5500, then I would prop it out to 5500. He told me it is hard on them to run them shy of the max rpm on a regular basis.

Thanks bluesea I think that is good advice.

I will contact a dealer and tej to find a prop to match or correct prop for this boat.