Problems

[MattMigues]

Originally Posted by CajunChristian

I have a Mega in my shop that looks exactly like your Yammie. Middle cylinder has aluminum galled on the walls over the exhaust port. This motor was operated in 5 degree weather with a frozen water system, it overheated. The plugs and the piston you show do not indicate a lean condition. A lean condition would turn the plug white and leave zero carbon on the piston. Usually a lean condition will gall aluminum on the intake side first. Overheating will gall aluminum from the exhaust side first since it is the hottest place in the cylinder.
The factory jets carbs for all conditions from 0-120 degrees, that's why most factory motors run pig rich. Carbs don't just suddenly lean out. Especially if it was running great just before it died. My guess would be overheating, frozen water pump impeller????? I would drop the lower unit and check the impeller. It may have been frozen and sheared the rubber impeller from the plastic hub. It will look normal, but try to spin the rubber portion while holding the driveshaft, if the rubber turns, change it out.
As for removing the oil injection GREAT IDEA. A pinhole in an oil line and you grenade a motor. Hand mixing is a 100% fix for that problem.
D

Frozen water did cross my mind a few times.