Overheat after throttle down...

[imported_Mike_M2]

I have a friends boat, Merc 350 Alpha, that runs great until you let off the gas and idle. Then it gets hot until you hit Nuetral and give rpm's. I just redid the entire drive, new pump, new risers, new Therm, still the same. Anybody ever have a similar problem?

 

[Chris1956]

Re: Overheat after throttle down...

Mike, It sounds like you have a water restriction. Have you checked the water intake grates on the outdrive to see if it is plugged? Also, in salt water (especially this year) the barnacles get into the water passage above the intake grate and below the water pump. I had to remove the gratings and stick a screwdriver up there to dig some of them out!

 

[tryan]

Re: Overheat after throttle down...

year?

 

[crazy charlie]

Re: Overheat after throttle down...

It is not uncommon for the temp to spike up upon deceleration and it should come back down after a few minutes.It will spike according to how hard and long you are running the motor and how abruptly you decelerate.Running at 4000+ rpms for 30 minutes and decelerating abruptly will result in a BIG spike in temp.I usually throttle down for the last couple of hundred yards still staying on plane and then run above idle for a while after coming off plane and plowing until I bring it down to a dead idle.This requires a little planning out when you are reaching your destination.This method usually results in a minimum spike in temp if any at all.Charlie