Re: 99 150 FICHT
The engines in question did not completely atomize and burn the fuel that was injected. The excess burned very rich and formed large carbon deposits that stuck behind the rings (much as any outboard would if it didn't have thermostats)<br /><br />This was more prevalent at extended idle. The engines that ran at mid-hi throttle positions, or didn't idle long, didnt see this problem.<br /><br />Once the carbon built up enough, the rings no longer had a "tension fit" to the cylinder wall, rather were forced to the cylinder wall causing undue friction and cylinder/piston damage.<br /><br />The updates include a "pinned" head and a spark plug chamge. This is a small "pin" that stuck out in front of the spark plug. This caused the fuel to atomize better making a more complete combustion.<br /><br />FYI: The Mercury Optimax saw the exact same problems...especially the 3.0L (200-225)<br /><br />If it(the engine you're looking at) lived this long, it didn't see the issue. It either never had a problem(likely) or the updates were done. I sure wouldn't be afraid of it, It may just be the best outboard you ever owned...<br /><br />Still... get it checked for the updates, or give us your model and serial numbers so we can check for you. ( remove one of the spark plugs, on the flat surface where the plug tightens against, look for a small pressed in pin and let us know what you find.)