Starting at the beginning.......

Hard starting and wiped out a starter could have been caused by some water in cylinder. Could have bent a rod then and it finally let go.

Bad fuel could have caused detonation, bent a rod, and it let go.

A friend had an engne come apart cruising at 3500rpms and spit out the bottom without any warning. It ran perfectly fine the entire day before and right up until it blew.

What I am really wondering is since I screwed up and layed the boat up for the winter with only 30 gallons in it could that fuel have turned to water because of the ethanol? And if so, would water in the fuel do this?

Ouch, rough start to boating season, hope all goes well on new engine!

Water in the fuel would make it run poorly, if at all.

I doubt that was the culprit.

Detonation. What did the tops of the pistons look like? Any of the ring lands lifted or pulled upwards, especially near the valve relief?

Think Griff is right about the water ....sounds like you might have ingested some water and that started the whole sequence of events. Water does not compress!!!!!!How close to the water are your exhausts and do you have internal and external flappers on the boat???Don't think your ever going to know for sure now but I would be checking the other motor and take preventive measures about it possibly happening again. good luck !

Jim

Exhaust is about 6 inches above water line when not running, yes external flappers. Water did not come back up the exhaust from outside the boat. My only other question which I have been avoiding is this.....zz502 GM performance cam is what I found in this engine when I tore it down. Not real big. .527/.544 duration at .050 in. for intake is 224 and 234 for exhaust with 110 LSA.

The boat had Stainless marine exhaust with standard risers (about as long as stock mercruiser). With the 110 LSA could it pull enough water back to do this if that was happening?

Again, 200 hours on these engines. So it has been fine for a while. The only thing I changed was lowered idle from 1000 to 750 and all of a sudden I have problems.

Pistons look perfect besides the spots where they hit valves when the rods came apart.

Do you treat your fuel?
I've winterized with empty, half, and full tanks, all treated with Star-Tron; and no issues.

The one year I had ethanol fuel in the boat, and didn't know it (or treat it)...
...problems.
Had to replace F/W separators, inline fuel filters, and fuel boost pumps; as they were all destroyed by the ethanol.

Went to Wal*Mart today and cleared out their shelf again:
http://www.walmart.com/ip/Attwood-8o...itive/16351036

I've had problems with Startron and Stabil - yeh, the green E-10 stuff. With carburetors - especially billet plated one's.

Got turned on to the following by member s30 when storing boat for winter : putting some 2 cycle engine oil in fuel seperator. Run till some signs of oil smoke out of exhaust. No doubt carb is full with the mix and fogged...lol.

BTW: I run several 2 stoke engines and use 40:1 ratio, so I use that fuel to fill the seperator. A splash of Green Stabil just in case.

No problems since.

I had 2 carbs get heavily gummed (white jelly crusty substance) 2 years in a row (well used boats) and noe not anymore.

Results my vary, but mine are great now.

==============================

About the OP's motor - oh boy !

My experience, a broken starter, especially if it broke the nose, is hydrolock. Have had plenty of bent rods from it, but not engine damge like that, but then gain, never rn one after finding hydrolock until the issue causing the hydrolock was fixed.

Oh, in cars have broken starter noses with not enough starter for the engine's compression and usually not so good of battery. LOL.