1998 ox66 225 runs rough at low rpms

I have an 225 ox66 .Starts up perfect.runs great but runs rough at low rpms as soon as it goes to six cylinders(1900 rpms) smooth as silk.

[boats.net]

Possible need to do synchronization and linkage adjustment, maybe a new set of plugs.

jim

I have had the same problem for some time. I have a 1997 250. If I ***** all day I have to change the plugs. Runs great at cruise but it don't want to idle at the dock. When I put in new plugs it runs perfect until I ***** for awhile again. I cannot fix that problem. I have done a decarbon, new fuel pumps, adjusted the oil mix, changed filters, and replaced the O2 sensor. I use Yamaha ring free, but if I ***** for 3 or 4 hours it carbons up the plugs and I have to change them. I hope someone has another idea that we can try. Good luck!

I was told by mechanics who have the motor thats how they run.I synchronized the throttle body linkage and the oil pump linkage. Oil pump helped the most. New pugs helped . Cleaned carbon from 02 sensor . I have the test lights for the motor ,all was good . Replaced thermostats . Just cant seem to smooth it out at low rpms . Txs

[Tucker]

Guys I'm not buying that. There are lot of guys that ***** these motors with no problems, bigfish you reading this??

[boats.net]

Those engines only run on 4 cylinders to about 1200 rpm's thats why sync and oil pump link arm adjustment is important. Jim you might try new thermostats to see if helps with plug fouling.