Thanks for all the advice guys. I hope to know more tomorrow. I think I'm going to go pull the valve covers and look for loose components. Hopefully that will be the problem, if it is I'll replace the cam and lifters. If I don't find anything loose in the valve train, I guess I'll run it on the hose and drop one cylinder at a time to identify the problem, and brace myself for the worst. I should be able to do the cam right where it is because everything is currently stripped out of the boat, anything else and the engine will have to come out.

pull the filter and cut it open and look for metal shavings first..that should give you a idea where to go from their..

The valve train is tight. I pulled the valve covers this afternoon and there is no significant movement in any of the rocker arms. All of the push rods look good. I might have a chance to stop back by there later. If I pull the filter and find metal then what? What if I don't find metal?

if you find big chips of metal pull it and do a tear down.. if not,,look else where,,are you sure its not the exhaust flappers? or somthing rubbing the bell housing?

This is a deep solid clunk noise I can't imagine exhaust flappers doing that. One thing that might be the culprit...a few years ago I added an oil cooler and perma cool t-stat. I'm not 100% that I have the lines plumbed correct, and I can't seem to find a schematc for either the Merc remote oil filter kit or the perma-cool stat. Does anyone have those? i need to know which port is the exit and which is the entry from the block adapter, and the same for the stat.

Metal flappers can cause a hell of a racket- certainly check.

pulling the cover and wiggling rockers doesnt really tell you anything-on a collapsed lifter the spring will still hold the arm in place- you need to start the engine and look at them.

safe to assume you pulled the plugs and looked for an obvious issue there?




Uncle Dave

Thanks for the info Uncle Dave. I wasn't sure if pulling the valve covers was a reasonable way to tenot. I didn't have the time to bring the engine home and run it today so no I haven't tried killing each cylinder yet. Hope I can do that tomorrow morning.

1. No metal in the oil filter!

2. Oil was a little milky.

3. I've changed the oil, verifing the plumbing for my remote filter/cooler combo then i will run it and pull plug wires one at a time to look for an issue.