Mercury 40FI Overheat Alarm at high rpm

[imported_Warren]

I have an 02" 40HP Mercury Fuel Injected 4 stroke on a 13ft whaler..

Paid to have the impeller replaced about 6 months ago (It was fine but replaced anyway)...And while it was at the shop they also did some "Recall" work....

When running at 4500 rpm's the alarm started buzzing. Checked the "Tell Tail" and water was coming out of it, felt the stream and it wasen't hot...

Slowed down and the buzzer turned off and started going again.....

Approached 4500 rpm's again and same situation.....

Runs like a champ but one of the times I felt like there was a quick, slight hesitation in the outboard right as the buzzer went off...

Any Suggestions on what may be the problem?

 

[imported_Warren]

Re: Mercury 40FI Overheat Alarm at high rpm

Would a sticking thermostat cause something like this to happen?

 

[Texasmark]

Re: Mercury 40FI Overheat Alarm at high rpm

Possibly, but most Mercs nowadays have bypass valves for high speed operation which is a much larger passageway and eliminates the stat as a culprit.

For the pee to tell you what the engine is doing, the water has to come through the powerhead to get to it, which all don't necessarily. I'd feel the powerhead to determine temp and since stats are around 140F so you should be able to touch the block anywhere and hold your hand on it for 5 seconds.

I'd say you picked up some crud somewhere.

Have you had this problem ever since you had the work done? Could be improperly installed impeller, wrong parts, sloppy reassy, or a timing issue.....did he tell you what the updates were? Any involve mixture or timing changes?

Mark

 

[imported_Warren]

Re: Mercury 40FI Overheat Alarm at high rpm

Thanks for the reply Mark....

I'm going to look for my receipt and report back with more info.....Warren