Re: 1995 mercury 40hp overheating.. this situation is baffling to me
Take down the LU and dis assemble the waterpump. Hopefully you will find any broken fins before they get shot up into the base which would require a power head removal. If fins are missing then be sure to find them all. Look under the metal plate as well. It may be the impellor is just weak. It may look OK but it doesn,t have the tension it did when new. When was the last time it was changed? Have you run the engine at all without muffs? Just trying to find some basic info and starting at the least expensive and most likely place for the cause of the problem. At present it,s a guess and a troubleshoot.I had a 79 2 cyl 2 stroke and dismantled a 4 cyl 4 stroke I have yet to come into contact with a 4 cyl 2 stroke so take it all with a grain of salt. Adding pictures along the way will help alot. The 4 X 4 was a 1997 basicly water pump principals are mostly the same with these mercury,s. Good chance you just need a new impellor about 23.00 ebay has plate and gaskets and housings and base plates if needed or you can get them right here on Iboats.com. Shipping costs are the problem when just purchasing a small item though. I,m usually on most evryday unless i,m out on my boat or shopping so feel free to post away with any concerns you may have. There are alot of decent well educated people in this site as well that enjoy helping a fellow boater.You do not have to be a marine machanic to fix this problem as you can see the one you had is clueless so time to take charge and get your fingers a bit dirty so you know what you have and what gets doen on your seemingly rare engine. I would love to see a pic of the electronics.