2002 OX66 Issue

[scott1963]

I recently purchased a 2002 boat with a Yamaha 225 OX66 engine. The gentleman I purchase it from rarely used it and it looks brand new. It ran fine the first couple times I took it out. The last three times I ran it, it started hesitating around 5000RPM. Almost like the fuel is shutting off intermittently. Under 5000RPM it runs perfectly. It would run up to 5600RPM previously without issue. I changed the spark plugs, checked the fuel filters, cleaned the O2 sensor, but it still does this. Do I need to change the O2 sensor? I have read many articles stating that this ended up being the culprit. This engine does not have many hours on it and when I cleaned the sensor it didn't have much residue on it. Any help would be appreciated. I also read that a defective O2 sensor can damage the engine if it's not corrected. Thanks,

[Tucker]

Believe you have fuel issues. Probably your HP pump filter cllogging. Lots here about same symptoms. Get a comfortable chair and do a search

[scott1963]

Okay, I'll start by checking the low pressure fuel pumps and go from there. (One thing I did notice is the primer bulb does not stay firm when I pump it up. I didn't think this was a big deal with a fuel injected motor.) Thanks,

[jb123]

yea prob lp pumps/VST... 02 will cause varying rpms
look at motor filter level when this happens
pump ball while running, should bog down motor or unbolt all 3 and pump ball, if any leak, replace

[scott1963]

I unbolted the LP pumps and pumped up the primer bulb. The middle and bottom pumps leaked fuel when I did this. The top pump did not. Evidently these pumps need replaced? Hopefully this is the culprit,