Mercuiser 305 Overheating Problem

[mmalone]

I bought a boat I believe has sat in a garage for some time. I know that a service center winterized the boat in the fall and drained and started it in the spring but it was not used through a few summers because of illness. Anyway I went fishing boat runs great after trolling at idle for a bit the temp runs up to 260* as soon as I give it just a little throttle cools down quickly . Any suggestions on where to start correcting this problem? Thank You

 

[v8power]

Re: Mercuiser 305 Overheating Problem

Likely the drive impeller. To little flow at low speed. replace the impeller.

 

[cr2k]

Re: Mercuiser 305 Overheating Problem

If it's been over 2 years it needs an impeller anyway. Start there.
What you describe is classic signs of bad impeller. Don't run it till it pukes or you will be chasing impeller blades all through your cooling system and if you miss any you will have overheating problems too.

 

[Bondo]

Re: Mercuiser 305 Overheating Problem

Ayuh,... Sounds like the Impeller died of old age,+ it's always the 1st place to start in an overheat situation....

 

[PitchFork]

Re: Mercuiser 305 Overheating Problem

I had the same problem with my '94 305 back when I bought it. I first got the impeller changed out and turns out it was pretty bad housing was warped and needed to be replaced. After the impeller was fixed I still had overheat problems at idle only. It turned out the check balls were missing from the T-Stat housing. I will be changing the impeller at the end of this season as it will be 3 years old and with 300 hours on it.