I have a 1996 Hunter 430, in which Sea-water made its way to the oil recently. The engine is a Volvo MD22L, which is now in pieces on a pallet in the shop. The heat exchanger tests out with no leaks, and the head gasket was intact. It was not coolant in the oil, but water. Earlier this season, I had it hauled out for bottom paint and some repairs. One of the items "replaced" was a step-down connector (from 3" to 2 1/2" hose) that goes to the exhaust outlet. It was a custom built part out of fiberglass. My mechanic and I suspect that water may have come in from the exhaust outlet, and that possibly the original step-down connector may have had a safety valve in it to prevent the back-flow of water. Can someone send me a picture of the rear of their engine and the step down connector (in-place)? I don't know what the original part looked like. Also, if you have any good knowledgeable contacts at Hunter, please share, as I would like to know if that anti back-flow valve really existed in the original part.