View Full Version : Sporatic Overheating

08-21-2007, 02:28 PM
"I have a 1992 Mainship 35 Convertable with twin MP 454's with just about 1010 hours on them.
As the subject states I have a sporatic overheating problem with the starboard engine. We typically cruise at around 3400 rpm and both temps run just below 160 degrees.
I've gone through the trouble shooting in the owners manual and have found nothing. I've flushed the raw water cooling and have checked out the raw water pump. The previous owner had changed the impeller in 05. The flows from both engine exhausts are pretty much the same.
Any other suggestions would be great.

09-27-2007, 07:35 PM
"Todd, how well do you know the previous owner? If you believe you will get an honest answer ask if an impeller ever disintegrated. When that happens pieces of the impeller can move through the closed cooling side. As a piece moves around it may get to a place it causes a clog. Although this does sound like a stretch for an intermittent problem. Also I change my impellers every spring. It may be over kill but 25 bucks is cheap compared to having one come apart.

Good Luck

09-28-2007, 08:43 AM
"Joe,Thanks for the reply!! I decided to pull the impellers on both engines. Not a very simple task considering that the pumps are crank mounted. there is only 2" to 3" of clearance between the pumps and fuel tank. The problem turned out to be a few of the impeller vanes were actually split (torn), no disintegration. I also pulled both head plates off of the heat exchangers and blew compressed air thru all of the internal tubes. I found just a little bit of miscellaneous debis.
Since the repair I have put on about 10 hours of run time with no problems.
I'm not sure I'll replace them every year, but I'll keep a closer watch on them!!

Thanks again,

09-28-2007, 10:10 PM
Good work!