reasons for F225 carbon buildup?

[antiguan]

Several weeks ago i reported a problem with one of my yamaha F225s. I coulnd't find anyone who had the same prob as i have had. I had perfect power and rpms but sounded a little rough at idle and also a Intake Pressure Sensor fault reading. We did a compression test and found one cylinder to be slightly low on compression. We opened it up yesterday to find plenty of carbon builup on all the backs of the intake valves with one sticking causing the low compression i guess. I get 6100 RPM at WOT and use mercury four stroke oil every 100 hours. I have gone 1300 in the past 15 months. We only get one option on fuel and they tell me its 93 octane. I dont know people who have ever had problems with fuel from this marina either. I run the engines at an average of 4400 rpms but do run them hard once a day. Why all the carbon on the backs of the intake valves?

[boats.net]

That engine was built to run on 87 octane gas, I don't know of anyone in your situation that has run that engine on 93 octane gas for that many hours. I can't say if the higher octane would cause more carbon buldup or not. You can add Ring Free to gas to help keep carbon down.

[Operaman]

Agreed. Ring free is an excellent product and is not only for 2 cycle motors. Seafoam is also very good and has many fans here also. Ring free is the Yamaha product. Why Mercury oil anyway ?

[antiguan]

we have a bigger merc dealer here than yamaha and they have plenty of merc oil at a good price. its designed for 4-strokes and since they also have had the same F225 then i figure its good enough.

[MTCFISH.COM]

Run Startron in your gas. It helps with the E10 issues and also prevents carbon build up.