200 ETXJ fuel problem

I am having a problem figuring out what is wrong with my port motor. I have a pair of 1986 yamaha 200s, one of which is burning WAY more fuel than the other.

The problem is with the port motor. At idle it will burn 2 GPH, at 1000 RPM it will burn 4 and at 1800 RPM it is burning 8GPH. At 4200 RPM it burns 12 GPH.

The starboard will burn 1, 2 and 3 at the same RPMs.

It sounds like it is misfiring until about 2500 rpm, then it smooths out. The fuel flow(measured by floscan) is not steady anywhere in the RPM range for the port motor, it is always moving up and down 1-2 GPH.

Lastly, it requires more throttle to match the RPM of the starboard motor.

I have check the compression, 112-120 psi. I looked in the carb throats for extra fuel. All of the spark plugs look fine, no sign of fouling.

This is a new problem, did not happen last month.

Sorry for the long post, but I am frustrated. It seems I can not figure out what is wrong. It seems like the problem is most evident at low RPM

Any guesses??

Thanks
Casey

[boats.net]

Check your fuel pumps for ruptured diaphrams.

I checked the fuel pumps thoroughly, everything is fine. The diaphragms look good with no tears or other issues.

Could it be the carbs? Seems like a carb problem would be too lean, not too much fuel flow. I have had a stuck float before. I could see it in the carb throat.

Could it be one of the coils? The spark plugs did not look particularly different. It does not appear one is fouled or not firing.

I'm baffled about this.

Thanks!
Casey

[jb123]

while on hose around 1200 rpms, pull each plug wire at a time, ensuring a rpm drop with each. if not then that carb>plug isnt running correctly . you can do the same with airbox off, use your finger to choke, listening for an increase in rpms.