Thread: 2005 Optimax 115

Is it a steady alarm ?

Yes it is. But only comes on at 4100 or above.

If steady alarm it's either water temp
warning or fuel restriction alarm, if temp warning try unplugging temp. sensor , some had 2 some had 3, but u need to make sure motor is not getting hot , if u have lazer temp. gun. If motor is not hot, sensors are known to go bad, by unplugging one at the time will tell u which one. Some of those models had fuel restriction alarm , motor has air compressor that pushes fuel at injectors , u can hear it at idle , sounds like a sewing machine. If intermittent alarm, make sure on board oil tank cap is on tight that tank has a alarm, that is a pressurized tank and pressure pushes oil to motor tank ,both have alarms , if caps are tight on tanks , and oil in both ( make sure u have oil in motor tank) if not , cap or caps on in board tank could bee leaking or pulse line from engine has a leak. If u have oil in both with caps tight , unplug 2 wires at in board tank and see, if that doesn't work unplug 2 wires at motor tank. Those floats can go bad

Thanks a bunch . Will try those suggestions.

My oil tank has a bad float and causes intermittent alarms. Disconnected right now but will be replaced later. Mine is an older 40 but the systems can sure be aggravating. Hope it’s just a bad sensor and you can fix it yourself.

My 225 opti did that a couple years ago. It was a bad float in the oil tank on the motor.
Disconnect the connector on the tank and see if it stops. If so replace tank and fill with oil.

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My guess is thermostat is sticking closed. If the thermostat closes you will still see it pump water it just won't flow around the engine jacket. Replace the thermostat.

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It could be your popet valves are not opening as the engine RPM`s come up they by pass the thermostats.

I do not think this is your problem but a good thing to know about the Opti`s

Have you replaced the water pump lately, Mercury recommends max every 2 years, they do not seem to wear out they get hard every time I have had to change mine it looks fine but the impellors are very stiff, the water tell tale never gives any indication of weak water pump.