2010 Mercury 75HP 2 stroke ELPTO alarm at WOT

[Ganastas]

on my last 2 outings an alarm has sounded when I ran at WOT. Slowed to neutral and alarm stopped. Alarm (continuous beep) would only sound again if I ran at WOT. All other speed/rpm ok. Water pump impeller replaced 6 months ago, thermostat and poppet diaphragm replaced 18 months ago. What is suggested procedure to diagnose the issue? BTW compression test readings 6 months ago was 130/127/127.

[JOE54]

at what rpm does it come on that mtr has over rev warnning module , ser number please

[Ganastas]

Around 5200 rpm. Serial number 1B826880. I don’t believe this motor has over rev warning as it has never alarmed in the 11 years I have owned it...

[JOE54]

test for overheat with infared temp gun

[Ganastas]

I assume you mean after alarm has sounded after running at WOT? Also is it normal for the alarm to immediately stop after putting in neutral? Or should it keep sounding until engines cools down I.e. after a few minutes?

[acesover]

Maybe your tach is off and not showing the correct rpm and that is your rev alert going off.

[JOE54]

I assume you mean after alarm has sounded after running at WOT? Also is it normal for the alarm to immediately stop after putting in neutral? Or should it keep sounding until engines cools down I.e. after a few minutes?

yes , not normal,should keep sounding untill cool down , has any work been done to control box that might have shorted wire in alarm system ???? still think module is problem , no much to go wrong on that system

[EuropeanAM]

Joe- correct me if I'm wrong, but I don't believe this one is equipped with a warning module (ie: Alarm sounds for low oil level or overheat ONLY, with no test beeps).

[JOE54]

no correction needed, i looked and that breakdown shows rev limit module for tiller and jet , so i think we have to eliminate whether its heat or oil related or wiring shorting do you concurr DR.WEED ????

[Ganastas]

No work done on control box. Only installed a new sounder in boat.

[Ganastas]

I have heard that the oil tank float system can be problematic. Could this be the early stages of float switch failure? I.e. triggered when operating boat at WOT?

[EuropeanAM]

You can pull one of the blue wires from the oil tank FOR TESTING PURPOSES ONLY, but I think you're going to find that it's overheating.

If you advance to WOT position, does the horn sound INSTANTLY, or does it take some time for it to begin sounding?

[Ganastas]

On my last outing it pretty much happened instantly each time I advanced to WOT (seconds not minutes)

[JOE54]

You can pull one of the blue wires from the oil tank FOR TESTING PURPOSES ONLY, but I think you're going to find that it's overheating.

If you advance to WOT position, does the horn sound INSTANTLY, or does it take some time for it to begin sounding?

+1

[Ganastas]

Thanks for all your input you have given me some helpful direction. What has occurred to me however is that this issue coincided with me installing new transom mounted transducer. The location hasn’t changed from the old one however the new one is a little ‘chunkier’ and might be sitting a little low. Have you come across transducer location / position as a cause for engine overheating due to increased turbulence?

[JOE54]

AB SO LUTE LY never ever ever never mount anything in front of gearcase that can disturb water flow to gearcase water inlets ever