harry wall
New member
I have a sea water cooled Yanmar 3GM30, 3 years old only 100 hrs engine run time. I replaced 2 of the 3 anodes 7 months ago (I only just discovered the third anode hidden behind the fuel pump). The previous anodes were about half corroded.
A few months ago I noticed some white powdery substance around the plastic screw that drains the engine block and a little around the head gasket. I wiped it off and recently checked it again. It is worse and appears on about 4 inches on one side of the head gasket, about 3 inches on the opposite side of the head gasket, around the engine block drain plug again and also around about 1 inch of the water pump gasket. The bilges are dry so not much moisture around. I'm concerned that the corrosion may be inside the engine and not just the outside where the gasket (presumably a copper alloy of some sort) meets moist air. I'm guessing the problem is galvanic corrosion.
The negative from the battery to the engine block is always connected but the positive from the battery to the starter motor is always isolated when not in use.
Has anyone had a similar problem and found a solution?
A few months ago I noticed some white powdery substance around the plastic screw that drains the engine block and a little around the head gasket. I wiped it off and recently checked it again. It is worse and appears on about 4 inches on one side of the head gasket, about 3 inches on the opposite side of the head gasket, around the engine block drain plug again and also around about 1 inch of the water pump gasket. The bilges are dry so not much moisture around. I'm concerned that the corrosion may be inside the engine and not just the outside where the gasket (presumably a copper alloy of some sort) meets moist air. I'm guessing the problem is galvanic corrosion.
The negative from the battery to the engine block is always connected but the positive from the battery to the starter motor is always isolated when not in use.
Has anyone had a similar problem and found a solution?