2005 Mercury 50 hp Outboard Motor Alarm Problem

[Justchillin05]

While boat is moving at high rpm, sometimes the alarm goes off and it won't go off until we stop the boat and turn the engine off. Once we re-start, it is normally off. We just replaced the water pump and the "pisser" is working fine as far as we can tell. We are adding oil as we need and that part seems to be fine. Could this be a control module issue or an alarm sensor issue? What should we check first?

 

[piibu]

Re: 2005 Mercury 50 hp Outboard Motor Alarm Problem

Check the thermostat and the temperature switch.

Thermostat:
Valve Opening Temperature: 136? F - 143? F (58? C - 62? C)
Full Open Temperature: 158? F (70? C)
Valve Lift: 0.12 in. (3 mm)

Engine Temperature Switch:
Above 131? F (55? C): No Continuity
Below 104? F (40? C): Continuity

 

[brettpeterson8]

I had the same issue with my motor last year. It was my thermostat. You can pull your thermostat out, put it in a sauce pan on your stove with water, and heat the water until boiling. If the thermostat doesn't open, it is shot. Your alarm is going off because it's getting to hot as your thermostat isn't opening to allow more water to pass through to cool your engine. Hope this helps.