HP 500 - Engine Knock
 

Boat just ran great. 5350 rpm's. Came off plane and heard knocking noise. No loss of power although when I went to shut engine off it farted and burped before shutting off. Obviously do not want to blow it up, but before I pull the engine I thought I would check here for suggestions on possible causes, fixes. Thanks.

Pull the valve covers and check the valve train. Next, just to start, do a compression test and look for low cylinders. After that you can proceed to a leakdown test if you find nothing else. Inspect your plugs as you pull them out to do your compression test. Kinda suck, but at least it's still running. I wouldn't run it again before you check it out real good.

Hope this helps.
Dave

Thanks Dave. Headed for the trailer. This may be a good excuse for a new motor! More POWER!

Mike,
Pull the oil filter off and cut it open too. That will tell a pretty good story if it is starting to kill a rod bearing or something similar.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

what about broken valve spring? will make some noise?

Do ya think checking the valve train?

Dave

OK, I am retarded. Turned out to be a bad header gasket. Took the boat up to Miklos and Jay Stuso (sp?), fired the engine and two seconds later they both said at the exact same time, "exhaust leak". Replaced the gasket and all is fine. I cannot believe how similar that sounded to a bad valve issue which I had once before. Oh well. Live and learn. Thanks for your help.

not really. happens all the time. thats why it is always helpful to look for a confirming symptom.. "if this is true then i should be able to go here and see/hear this" sort of thing.

there is a 3 page thread on another forum with a guy who claims he has terrible "ping" above 3500 rpm ... yet he has changed everything, checked everything and the plugs all have color on them...

for my part, i still think he is hearing something else completely unrelated...

good for you with your gasket.

great news....maybe you should buy a lottery ticket !!!! Rob

No kidding. I also have to give a shout out to Mercury Racing here. The HP 500 in the boat is the same one the boat had when it started racing Factory 1 in 1997. And the boat was always run really, really hard. Still pushes the Corsa 80 though so you gotta love it!:drink: