Mercruiser 470 repower 1978

[Destroyer]

Originally Posted by aussie

Sounds like you have a head gasket leak caused from a corroded head or block could be only gasket What you have done may work but all it will do is cause the leak to get bigger quicker .Yes your engine will never get hot now and long as you know that when you have water problems from leaks out of the block you wont be able to fix them.Also all that sealer you put in the cooling system will no longer seal what it use to as the salt water is affecting it and the leaks you have may of started because of that..I would keep a eye on it all the time as it may get worse and start filling your hull with water make sure you have a working pump lol

X2

[surchin]

Hey guys OP here .... thanks for the input. It’s 4th July 2018 and so far so good with the merc. I was hoping to get another year out of it and things seem to be running well. I use it pretty regularly at least 1-2 times a month to keep it going. The overheat was just such a bust I would recommend a raw water bypass to someone as last resort.

My theory is that I had a small leak behind heat exchanger between block and head that was causing loss of pressure and it would boil over. Couldn’t see it with heat exchanger mounted. And fluid coolant boil over masked the leak.