Offshoreonly.com - 502 Catastrophic Failure!!! Why does this happen?

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Lowering the idle down to 750 could certainly cause reversion if it was on the edge. The lower the idle, the more possibility for reversion. It sounds like it may have had some water in it when you tried to start it and it killed the starter. It's also possible that it bent a connecting rod. Once it killed one rod bearing, then the other one on that journal doesn't have a chance, You are then putting metal through the oil system, which can cause others to go. Were the tops of the pistons clean, like they had been steam cleaned? That is an indicator of water
Eddie

Quote:

Originally Posted by Baja226sport (Post 4146800)

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.

I'm wondering if you are on to something. That cam would certainly be prone to reversion with that tight LSA. Slowing the idle down to 750 might have been the tipping point to reversion. However, this would only tend to happen at idle, not high RPM's. Perhaps as Griff suggested you ingested enough water trying to start it to damage the reciprocating assy, and it let go under load. I would check that other motor out very carefully. If it's running the same cam, consider switching it or the exhaust.

Is it the same motor that was the subject of this thread?

http://www.offshoreonly.com/forums/g...-pressure.html

Quote:

Originally Posted by donzi matt (Post 4146879)

Is it the same motor that was the subject of this thread?

http://www.offshoreonly.com/forums/g...-pressure.html

Oh schit !

Good csi !

Where is the nutkick smiley when you need it ?

Lack-o-lube even turned the crank blue .

Quote:

Originally Posted by Baja226sport (Post 4146658)

The boat ran great last year, this year first time out ran a little funny. Then was hard to start. Then wiped out the starter. Thought I had bad gas or something, added water zorb and it seemed to be running really well again.

3rd time in the water and after taking a swim break we decided to end the day with a little cruise. Ran it up to about 4900 rpm, no trim yet or anything, temp was good, oil pressure good, then pop bang smoke, not running!

Could bad fuel do this? I am just at a loss for what happened.

Definitely looks like Hydro lock to me..ingested water

:throw::throw::throw:

Yes, a motor can make a lot of hp on nitromethane

No, you can't just pour it in the tank and go....

Of course, when you run it 4 1/2 quarts low, problems happen.

Quote:

Originally Posted by Baja226sport (Post 4146774)

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?

IMO, not likely. I've had water in my fuel before. Water filled up the water sep filter and then engine would not run. Had to dump the filter abut 3x to get all the water out.