I'm still battling an overheating Volvo Penta 170 inline 6. It overheats almost immediately after starting. I've confirmed good flow through the entire cooling system and good impeller on the sea water pump. The thermostat is good, and it overheats whether or not the t-stat is installed. I Was able to isolate the cylinder head and block from the rest of the cooling system and pressurize it. At 15 psi it loses pressure very slowly (probably took 15 minutes to drop from 15 to nothing), and there isn't evidence from what I can tell of water getting into the cylinders (rule out head gasket?). What else would cause this overheat? I have noticed when i drain out what water is in the engine, it's grayish in color, with a very slight oil sheen, and there is some sediment or something that settles to the bottom of a jar that I used to collect the water. when shook around, the sediment acts like sand in water....kicks up, then settles back down. Where do I go from here? Thanks.
