I have a mercruiser 3.0 that gave me some trouble last week. I after doing a leak down and compression test I decided to pull the head off. When I removed the head I first noticed that the 4th piston had about a 1/2 in hole burned in the center of it. I then noticed a blown head gasket all the way through by that cylinder. When doing the I am going to replace all 4 pistons and have the cylinders honed/bored out. The cylinder walls actually look very good. I did notice some black carbon like build up on a couple of the valves. What do I need to look for? I am wanting to find out why this piston burned so it doesn't happen again. I am not looking to go through a comple break down rebuild right now. I really can't afford much at this time. I would really like to just make it til winter. When the motor went down at the lake I did drain a lot of water through the drain plug. Lot more than usual. Would that have occured when the head gasket blew? When it went down we did have to idle all the way back to the boat ramp. The boat would still start up and idle fine to make it back. It would take any throttle though. Any help would be greatly appreciated.
