1999 Mercury 40 hp 2 stroke Overheat

[Scoggs4]

‘99 mercury 40 hp 2 stroke overheat alarm sounds after 5 mins of running. Has yet to sound when in gear WOT. Typically sounds only in idle after warmed up. Telltale has water coming out. I have replaced impeller (including housing/gaskets), tested and confirmed thermostat opens. Removed thermostat and ran, alarm sounded same as usual. Water comes out from top cylinder brass plug and bottom plug when tested. Will shoot block with infrared temp gun soon to confirm temp. What am I missing?

 

[CPTV]

On my 1991 60hp. Per service manual, the alarm will sound for overheating, low oil(sometimes the float will stick) or high voltage. After replacing the water , and thermostat, checked my float in the oil reservoir. I then checked my voltage and my motor it’s putting out over 17 volts trying to charge my battery. Hope this helps.

 

[Scoggs4]

I deleted the oil tank/alarm. My manual says nothing about high voltage alarm.

 

[CPTV]

I deleted the oil tank/alarm. My manual says nothing about high voltage alarm.

Message me you email and I will send you a screenshot of mine. Mine is older than yours but surely yours measures voltage as well.

 

[Scoggs4]

Can you put the screenshot on here?

 

[CPTV]

Can you put the screenshot on here?

 

[CPTV]

here you go. It kept saying the image was to large. But it finally worked.

 

[Scoggs4]

Thanks but my motor doesn’t have that

 

[faztbullet]

Remove the t-stat and look into housing on block . The passages on left & right maybe restricted or t-stat defective.

 

[Scoggs4]

Remove the t-stat and look into housing on block . The passages on left & right maybe restricted or t-stat defective.

Passages look good. Tested tstat on stovetop and opened at correct temps. Ran motor without tstat and got alarm too.