omc engine knocking

[craigkesler]

I recently purchased a 1986 forester with a 4.3 omc in it. Engine purred like a kitten when I bpught it. I took it out last night and after about a 3 mile run under full power, the engine developed a slight Knock. The knock comes and goes, and is mostly when running 1500- 2500 rpms. Any suggestions or help?

 

[byrontony]

Re: omc engine knocking

Have you changed your drive lube recently?

I only mention this because I once thought my motor had developed a knock, so much so I pulled the oil pan and checked all the rod bearings. It turned out my upper unit was toast and was making the knocking noise. I had filled it from the bottom port like so many others..

 

[sw33ttooth]

Re: omc engine knocking

I had filled it from the bottom port like so many others.

yea, filling my cobra was kind of odd to me for the first time because i've done outboards you fill form the bottom cobra you fill fromt he middle.

start with the prop does it have only that 1/8th inch of play or a little less? is it dinged or damaged?

i would then check your esa setting it may be off a tad bit and stumbling your motor, fast easy check, once in gear shut motor off does the micro switch sit between the fingers if so its good.

then i'd head towards your lower unit, pull the dip stick form the top if its good looking and full then dont mess with it.

check timing, might be that hair out of wack.

then id check out your fuel system, make sure accelerator pump is good and carb is clean.

after all that i might pull the heads and look at the valves and rods double and triple check them before your reinstall.

there are quiet a lot of problems that can cause knocking i just tried to give you a few hints where those omc gremlins hide.