Why these plugs are out is still suspect so you are right, it could involve
any of them. The boat owner seems pretty certain that the engine did not
freeze so it's still a mystery to me. I've never seen these come out as the
result of anything other that freezing or corrosion. The ones at the sides
are very low in the cooling jackets. I suppose defective installation is a
possiblity.

"Tim" wrote in message
oups.com...

James wrote:
I agree that it's certainly a good idea to get them in to make
sure there are no other problems but similarly I would not pull the
engine
just to replace a couple casting plugs. He's not going to be in a
position
to pull the engine himself and a yard will charge him a grand or so to do
it.

Please remember though, that there are two plugs on the back of the
engine between the block and the flywheel.

Obviously that if a couple plugs are damaged, there may be more, and
water could eventually seep from the back of the engine, so the engine
would have to be removed.

Also a head gasket could be leaking. I've seent hem not leak coolant
into a cylinder, but be lieaking to the outside.

Highly improbable, but not impossible.