pulled the exaust manifolds off my 4.3l, omc. no signs of water in the ports that mount to the head. water passages almost totally closed at exaust end. almost no flow. spent 2 hours opening them up. tested both manifolds with keroseen. no leaks. re-installed, and bay tested. full performance from motor, no overheating. however, there are still signs of water in the oil. (this was a problem even before the overheating). oil level continues to rise. can't find the source. where do i look next? head gaskets, intake manifold? cracked block? other diagnostics: good compresion all cylinders, idel had to be brought up just a bit after the overheat.
