Well honestly, I'm not sure what's going on...long story, but here goes:
Back in October, I forgot to put my plug in the boat, wound up getting towed in. Later, engine started and idled fine, but I discovered water in my oil. Took it to a shop, and mechanic immediately diagnosed that my problem was the "foghorn" style manifolds/risers that Mercruiser put on late-90s engines for only about 4 years (apparently a bad design which corroded too quickly?).
I had him replace with a new updated kit, and it supposedly cranked up and ran fine. When I went to pick it up the next day, he said he had cranked it up again to check for water intrusion, and after a minute or so, it sputtered and died. He then discovered water in the oil again. So he's thinking blown head gasket (best case, scenario?), cracked head, or cracked block.
Last I talked to him, he said he took out the spark plugs, unhooked the outdrive, but can't get the engine to turn over.
He's now on vacation 'til the first of the year, and will get back to it then.
Thoughts, theories? Thanks!