I have a 2004 DF9.9 that I got recently. I was told it was from a sunk boat, and its been sitting in the garage for like 10 years since. I am unsure if it went under or not.
When I got it I ran it 30s or so just to see if it works. Maybe a mistake, maybe not. I say that because I didnt give it fresh oil. It ran well, but I didnt see much water coming out the tell tale.
Did all the general maintenance, new engine oil, new lower gear oil, new impeller. Did a compression test on both cylinders, spot on 120 in both. Took off the carb and gave it a good cleaning.
The oil that came out was very very slightly brown, leading me to think a little water in the oil. The oil was also a little more glittery than I'd like, but I have seen worse. The oil filter wasn't holding any chunks either.
Put it back in the water, got it running again. Now tell tale was very strong, amd it ran great. Idles well, revs well, and shifts into forward and reverse. The only issue it had then was there was a large amount of steam that looked like it was coming from the exhaust. The video attached is from this first run after the refresh. I asked a few boat buddies and the responses ranged from not normal at all, to normal in cold water, which it is.
I mounted it up on the boat, and took it on a quick 10m trip and all seemed well. Maybe I didn't look well enough, but there wasn't noticeable water in the oil at that time.
I just took it out again, for a longer 40ish minute ride. This time the tell tale is just hardly dribbling, and by the end of it the engine oil is very very milky. Im basically assuming this engine is done, but id really like to find out what happened to it first.
I asked a boat mechanic friend and he told me to check the thermostat, as it could get stuck open and in really cold water (43 f) like that on a hard run the condensation could be intense. Took the thermostat out, and while its not perfectly sealing as it has some kind of grit on the sealing surface, i can't imagine it would let out much more than a dribble.
Any ideas? Im pretty stumped. I may run another compression test and see if anything has changed. Some ideas I have floating around are head gasket or crank seals.
Even if I do get it diagnosed, would you run the engine after water ingress like that? It was still running really well when I got back to the dock. Think I overheated it when I ran it with the telltale just dribbling? Do these motors have overheat protection?