Merecruiser 3.7 170 engine clank on shutdown

[nailbender]

Hello. I'm new here.<br />I have tried the search feature and the other recommended helps before posting.<br />I have a 1986 Mercruiser 3.7 170hp that when I shut the engine off makes a clanking noise from the front of the engine.<br />It sounds normal while running.<br />I was getting the thing running for the year today and this popped up.<br />The noise was not there when I quit using it last season.<br />I listened in different areas of the motor while shutting it off to locate the noise and as near as I can tell it is coming from the flywheel/harmonic balancer area.<br />I have put a socket and ratchet on it and turned the engine back and forth. I can feel a little play and if I turn the engine over by hand I can get it to make the noise.<br />I can feel it in the flywheel as well.<br />My first thought was that the timing chain is loose or the tensioner is bad.<br />I'm wondering if a loose magnet on the flywheel could cause this noise from the magnetic fields switching.<br />I work as an auto mechanic so I have experience with engine noises, but this is new one on me.<br /><br />Thanks for any help.

 

[olbuddyjack]

Re: Merecruiser 3.7 170 engine clank on shutdown

Hi bender, welcome to iboats.<br />I don't have any experience on that engine but I recall reading something about the magnets dropping off in another post. Sounds like you might be on to something. <br />Go to the top of the page and do a search on this forum and see what comes up.<br />Hopefully someone else will jump in here with some good info.

 

[rodbolt]

Re: Merecruiser 3.7 170 engine clank on shutdown

carefully inspect the magnets on the altenator rotor, thats what you car guys call a harmonic balancer on the 3.7. sometimes they fall apart and hit the stator. also insure the stater drive is retracting and not hitting the flywheel. this motor is a bit different than any car motor ya ever monkeyed with. buy the faactory shop service manuaal and it will help. its an odd conglomeration of parts and pieces designed by MERC not ford, even though some parts are used from ford. was only in production a few years then dropped. only 2 big design faults I ever noted was the seals on the circulating pump and the open deck design. both were bad and no way to fix it.

 

[nailbender]

Re: Merecruiser 3.7 170 engine clank on shutdown

Well I got the flywheel off and found a loose magnet. Boy did that thing pull hard!!!!!!!!!<br /><br />Thanks for your help

 

[MrBill]

Re: Merecruiser 3.7 170 engine clank on shutdown

Nailbender...welcome aboard. If you find yourself needing to put any money into the magnets, stator or other compnents of the charging systems, nows the time to convert to an alternator for under $400. The only regret I had was not doing it 5 years ago.<br /><br />Glad you found the problem, it's common on the 3.7 L IL 4cyl.

 

[glasstron_19]

Re: Merecruiser 3.7 170 engine clank on shutdown

I just pulled my harmonic balancer and most of the magnets were gone..was wondering if Im gonna remove stator anyways can I run engine without all of the magnets..or will it throw engine out of balance..Thanking You I am..already had put an altenator on it a few months back charges well...

 

[Don S]

Re: Merecruiser 3.7 170 engine clank on shutdown

Welcome to iboats, You really need to start a new thread of your own, and not drag an old 2005 thread out of the archives and stick your post at the end where it will be lost.