502 Catastrophic Failure!!! Why does this happen?

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07-01-2014 | 10:51 PM

#31

Griff

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Joined: Oct 2000

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From: Omaha/LOTO

Quote:

Originally Posted by Baja226sport

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.

A 250rpm drop at idle could definately cause the engine to revert water more easily, especially with ZZ502 cam.

07-01-2014 | 11:03 PM

#32

motor

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this,to me seems to be the big question

Quote:

Originally Posted by donzi matt

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

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

07-02-2014 | 05:21 AM

#33

Baja226sport

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From: PA/MD

Quote:

Originally Posted by donzi matt

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

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

No sir, that one is currently in the garage taken apart. A friend was going to use it but we decided that it will most likely be rebuilt this winter to be a spare.

Should have added, that thread was not even about the same boat. Sorry for any confusion.

Last edited by Baja226sport; 07-02-2014 at 05:23 AM.

07-02-2014 | 05:40 AM

#34

Black Baja

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From: bel air, md

When it was hard to start to it just crank and crank and not start or was it difficult turning over and broke the starter that way?

07-02-2014 | 05:53 AM

#35

Baja226sport

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From: PA/MD

Quote:

Originally Posted by Black Baja

When it was hard to start to it just crank and crank and not start or was it difficult turning over and broke the starter that way?

It would spin and stop. Then spin over and stop. And if I tried giving it gas it would make a a chirp and pop through the carb and stop.

Then after sitting 20 mins it fired up like nothing ever happened.