Hi Guys, New to the forum, and I have what I think is a pretty interesting issue, that I cannot find anything at all anywhere on the net about! Boat was running perfectly, it suddenly made a clunk then went into neutral then stalled under low revs. I waited for the engine to cool down, checked the oil, visually checked what I could and everything seemed fine, oil level was perfect, nothing milky from the filler cap. Could not get it back into gear no matter what I tried so waited for a tow. I got towed back from the bow with everything turned off. Got to shore, started engine, still not forward or reverse just a loose throttle, there was a low pitch whirring from the stern drive so I turned the engine off, trailored it then drove home. Its a 3 hours drive through steep uphills and downhills. Did not check anything else after this point. Took the boat to my marine mech and they got the alpha drive going back into gear said it was a sticky selector and that was sorted. They then did a check over everything, only to find roughly 3L of clean water sitting under clean (not milky) oil in the sump. No one could figure this out, every mech I speak to says if there was 3L of water sitting in the sump the oil would be 100% milky if the engine had've been running while water was in there. Yet, theres not an obvious passage for that amount of water to enter the engine? Not that I can think of or see from my research and knowledge. Exhaust manifold and riser seem to be fine, compression is 140 icyl 1,2,3 and 100 in #4, so theres an issue there but surely 3L cannot make its way down the cylinder past the rings unmixed. So I think I have to rule out the manifolds. There was no water sitting in the head or in the exhaust manifold when removed I guess my question is, after being towed, could enough water end up in my exhaust, then find its way into the engine somehow driving up and down hills for 3 hours? And if so where could that happen. My trailor is a nightmare to get the boat high enough on and the winch cant pull the full weight so I need to try 3 or 4 attempts in deep water to get the bow high up front. Maybe water creeps in while thats going on? Its a very strange situation for us, but maybe someone out there has seen something similar before? Any help at all would be greatly appreciated! As for the back #4 cyl, I plan on doing an engine swap over winter, however want to sell this current 3.0 merc, running but as is, currently the engine runs like a dream. Would love to sort this out, get it in the water for the rest of the summer then swap it out for an LS1 over winter.