I posted this over in the jets section, for all that were curious, as to what happened at the river a couple of weeks ago.
I am posting over here because now I need some opinions.
Two weeks ago, I was making a pass on the river. At 5100 rpm, the engine abrubtly shut down. Tried to refire and it would not turn over.
Got a tow back to the beach, and pulled the dip stick and oil looked fine, pulled all the plugs, and plugs were fine, no wetness to any of them. Tried to turn the engine and would not move.
When I got home I pulled the motor, drained the oil, and imediately, I could see the rod cap, lying in the pan.
I pulled the pan, and what a mess. Rod and piston parts laying in the pan, along with some block material.
I put it on the stand and fliped it over to see the carnage. I took pictures and this is the results.
Pulled thew valve covers, and every thing looks normal to the naked eye, nothing appears bent.
#8 rod was broke and wedged between the crank and block.
#8 piston was broke and the wrist pin boss on one side was partia;lly broke out.
#8 cylinder has a chip out at the bottom of the cylinder
rod journal on the crank looks pretty bad
#7 piston is banged up prety bad
#7 cylinder has a gouge in it
I pulled the heads, and that is when I saw what I didnt like!
Looks like all the exhaust valves, have had light contact with the pistons.
#8 exhaust valve has a heavy contact mark, and #8piston and #8 combustion chamber have a contact scar scar in the same place.
The engine has less than 10 hours on it. I have never been able to spin over 5200, with an aluminum Berk AA.
To my Knowlege, I have never had the pump unload and over rev.
I have been out 3 times this year, and twice before the other boat got wrecked,and have not ran the boat much, either time.
The weekend that it broke was the hardest I have ran it since it was built.
I took the shortblock and heads over to the builder, so that he could have a look at what seems to me to be a valve/piston clearance issue.
The builder is of the opinion that all the exhaust valves had to have cotacted when it broke and that there is no way that they could have touched other wise or in the event of being over reved.
The engine was built, shooting for 11:1, but realisticly is probobly a little under. I run 100 0ctane in it and have mixed 100 and 93, once. I dont think two full side tanks have even been ran thru the engine!
Here are the pics of the carnage.
What I am looking for is truth about the statement of the exhaust valve contact.
Could it have been Detonation?
Could piston/ valve contact have wiped the bearing and the the rod failed?