I have the same issue as this guy.....

http://www.offshoreonly.com/forums/t...verheat-2.html

At idel the temp will rise but if I bump it into nuetral and give it some gas it will cool down.

I was told to check the transom plate nipple for corrosion, so I pulled off the inner hose today. The nipple is plastic and there was a piece of rubber hose to act as a bushing to fit the inner diameter of the hose....is this normal? I feel probably not, but haven't had a chance to check my manual yet, at work.

Also, this is an 86 engine in my 88 Cobia.

Any help would be greatly appreciated.

take the hose off where it feeds the thermostat housing. run engine. should be nice fat stream of water. at idle u have very little cuz your water pump is shot. if pump is new, check rubber fitting copper tube goes into above pump in upper housing. i had a friend who knew what he was doing but got that bushing halfway down copper tube. engine ran hot forever-till he killed it and sold it back to me!!

So I have to pull the upper housing to check it out?

Got an SEI Alfalfa drive that was missing one of the tubes. Didn't realize it (call it sometimers or trusting) until I test drove boat and it would heat up bad at idle but drop temp as soon as you reved it up a little.

Didn't check with SEI to see if they where supposed to send those or not (did buy full drive which comes in two halves) - just took them off the old busted Alfalfa. Problem solved.

I'll have to look in my service manual.

Thanks for all the help.

Lower housing. You can leave upper on boat. Makes it easier.

Here is one of the biggest hook-ups someone can give you for all this sort of stuff:

http://www.mercstuff.com/howdoi.htm

You are welcome. LOL.

BTW: Page for the Alfalfa water pump DYI is here:
http://www.mercstuff.com/waterpumpinst.htm

What you have back in transom area is normal depending on serial. #. IMO you need a whole complete impeller kit and the bottom base as well. Another wise change but not persay your issue at the moment is to change the water circ pump. A lot of older boats still have the original and run warmer than they should because of it.

Order the complete impeller kit and base, install it correctly as that should clear up your issue.

Can that plastic transom fitting be upgraded at all? I have the same setup and don't really care for that plastic fitting.
Thanks.

I just cured this same issue. The fix was the impeller and housing replacement. After a while, the impeller fins take a set in the curved position and the pump doesn't flow its rated capacity at low RPMs. An interim fix for me was pulling the two small hoses on the top of the thermostat housing which run to the risers and removing the plastic ball check valve there. I gave the springs which hold the balls on their seats a little stretch and reassembled.