I hope you guys dont mind helping me out with this problem I have, so here goes. I have a 500 hp mercruiser roller motor and the problem I have run into when I crank up the motor I can hear a slight knock coming from the valve cover. It will rattle for a few seconds and then go away at idle and completely dissappear. But then when I kick up the rmps to about 1800 the rattle will come back and then go away and maybe around 20 seconds later it will come back and go away again. I took the boat to a local mechanic that said I just need to go run the piss out of it. He thinks its the lifter sticking. Ive got over 12000 dollars tied up in this motor. Any suggestions and do you think if I put an additive in it would help, and if so whats the best additive to use.
This is from my limited experience. It's my experience that when you have one sticking that you are better off simply replacing it. Sometimes additives seem to work and othertimes not. Sometimes the problem is one that you simply can not diagnose from listening. We pulled apart of friend of mines 400 the other week. It appeared by all normal guesses to have a sticky lifter. It was sticking. In one position which allowed the cam to wear a groove in it which in turn rounded off the cam. It's not a major job to at least have a look.
Somebody who tells you to run the piss out of it probably doesn't have 12K of their own money tied up. Back to hot rods
It's a roller lifter,may be a slight possibility the roller has gone bad.If the little wheel gets ****ed your engine's gonna be in deep ****.Now,it may be just a little sticky hydraulic action but unless you're absolutely sure it's just gummed up,you might consider checking out the lifter.
We've seen this before.....buy a couple lifters and replace the hurt one. Chances are the extra lifter will become useful down the road too. Throw the hurt one away so it doesn't get reused. -Bigchief.
Don't know about rollers, but an old trick that has worked for me in the past. Put in a quart of ATF, seems to clean out hydralic lifters pretty good. Of course it won't work with a damaged lifter.
The Jalopy Journal
