Max Temp for Mercury 40 HP (Overheat Alarm Issue)

[bbrad99]

I have been battling an overheat alarm issue when I push my engine up close to 5000 RPMS. Boat runs fine lower RPMS. Once alarm goes off, I throttle down and it turns off after about 10 seconds. I can recreate the alarm anytime I get up close to 5000 RPMS. Had impeller replaced twice by two different boat shops. I am installing a water pressure gauge this week so I can see if there are any changes when I go up to 5000 RPMS. I was also going to use a thermometer to measure the block temp when the overheat alarm goes off just to confirm it is in fact overheating. Would like to know what the average temp should be when running full throttle.

94 Mercury Serial 0G03800 Model No:1040412PD mounted on a 24" Pontoon
Prop is 48-73134-A40-12P

 

[sam am I]

Do those engines run poppets? If so, I'd be headed there........

 

[bbrad99]

Hmm. Not sure if my engine has one of those or not. I do know my engine does not have a thermostat. Any idea where it would be located?

 

[sam am I]

The poppet valve if one exists? No, but lots of other folks here do, I can guess at like the base of the PH tho.......Give it a little time or google/youBoob it.