Engine boiling

[tb1]

I just bought a 1985 sunrunner 18' boat with a Mercruiser 140 engine. The model # of the engine is MCM 140, s/n A412106, 181c.i. 3.o liter 4 cylinder. I put the flush muffs and garden hose on it and ran it for 3 to 4 minutes and shut it off. The temp gauge was up to about 200 degrees and it sounded like something was boiling in the engine. Is the boiling sound normal and what should the temp gauge get up to? I'm a mechanic but I work on construction equipment and don't know much about boat motors. Also the boat has an oildyne trim/pump in it. The coupler between the pump and motor is cracked and needs to be replaced. I've got the sierra p/n for it (803852) but can't find anyplace that sells them. Any help would be appreciated
Thank You
Terry

 

[Bt Doctur]

Re: Engine boiling

135-140 max for temp.was the impeller replaced in the drive?

 

[Fireman431]

Re: Engine boiling

The boiling is not normal and neither is the 200? temp. It should run between 160?-175? (not sure of the specs on your particular engine). Others will give you specifics.

When you were flushing it, did you see water coming thru the exhaust? Has the impeller been recently replaced? That would be the first issue to check on before you get into manifolds, risers, head gaskets, etc.

Good luck.

 

[Bt Doctur]

Re: Engine boiling

http://www.boatfix.com/merc/Servmanl/13/13covr2.pdf
this might help

 

[jerryjerry05]

Re: Engine boiling

Iboats has your part.The sound you heard is a very hot engine.160deg is operating temp.Fill out the profile.J

 

[Don S]

Re: Engine boiling

While that service manual that Bt Doc posted will work in most cases, it's for the newer 90-97 models. Here's the link for the manual for your 85 engine.
http://www.4shared.com/document/hh5Z9V47/Service_Manual_10.html

The first thing you check in any overheat of a marine engine, is the impeller in the outdrive.
If it's more than 2 years old, it should be replaced anyway. Here is how you change the impeller in your drive.
http://forums.iboats.com/showthread.php?t=387864