Ok here goes. went out in the boat one afternoon was running up the river. Motor got to about 4600 and pop through the carbs. I shut her down. Popped the hatch and foam was comming out of the breathers. Had alot of condinsation on the blower,intake and valve covers. Checked the oil and it was dis colored but not frothy. So we sat for a few. then fired the boat and watched the oil pressure and water temp. All was good. so off we go 3200-3500 all the way back long run 45 min or more. Oil pressure and water temp never changed. Checked the oil when we got back and it was more sis colored but not frothy. What could this be from? Motor only has about 15 hours on it.

Motor is a BBC 515ci 8/71 around 6psi boost.

It sounds like it could be a head gasket or a intake gasket on the intake manifold. The head gasket could be leaking between the water passageway and cylinder. A leakdown test could elimanate the head gasket.

Thats what I was thinking. I orderd new intake and head gaskets. But the pop through the carbs would the gaskets have anything to do with that or is that timming.

I'd say once you find out if its the gaskets then run it and see if it still pops.

Ok I will. Thanks

What about risers? Could be a simple fix here.

Risers? Im running water jacket lightning headers. Maybe a header is leaking?

The concern is are the risers pointing downward or strait back. If it is strait then water is running back threw the exhaust valves.

here is a pic

The headers look like there in good shape i cant tell how much drop the exhaust is do you have a flapper on the tips to keep water from coming in when you come off plane. It could be a cracked header but chances are not.