Had the 455 in my Rogers rebuilt a couple years ago and took it out to run it around. After about an hour we noticed moisture coming out of the breathers and checked the oil. Water in the oil. Pulled the intake and changed the manifold gaskets with good gaskets and sealed them up real well (didn't see a smoking gun though). took it out again and after about 20 minutes. . . water in the oil again. I pulled the heads last week and couldn't see anything visible (manifold gaskets and head gaskets looked fine). I see this is a fairly common problem but haven't seen what the problem is or how to fix it. I'm planning on sending the heads out to be checked (anyone know a local shop in Anaheim area?) Any information would be greatly appreciated!!
Usually this condition is a exhaust problem or head gasket. If you are running
thru transom exhaust, the first thing to do is inspect the exhaust tip flappers.
If these are old and stiff or burnt, they will let in water from out side the boat. If the flappers are ok, you may have a leak inside of the exhaust logs.
The only way to find out is to take off the manifolds and disassemble and
pressure check with water. I have had all three problems at sometime.
Good luck.
Nice and Easy
check the water pump cover for corrosion on the inside. That's one of the areas that is often overlooked on a rebuild.
If you have a valve between the pump and engine, make sure it's not open all the way and letting too much water into the system. Another common issue.
A pressure regulator might help also...
Or a relief valve at the back of the engine. I tapped into the back of the intake manifold, plumbed them together to a T, then ran it to a valve and a through-hull fitting. Reduces water pressure, and allows you to fine-tune temp.
Thanks for all the help. I now have some work to do.
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