1999 25 mercury 2-stroke alarm

The alarm on this thing will go on and off when i first start it. Then it will stay off during warm up. Then past half throttle it comes on and off intermittently. Is this a temp alarm? The water comming out of the discharge hole is hot but not so hot i can`t put my hand under it.

Re: 1999 25 mercury 2-stroke alarm

So, is this an oil injected engine? Mercs have a reputation of having the low oil sensor fouling. If it goes south a long steady tone will come on when you turn the key and stay on. It's pretty annoying. I bought my boat with that problem. The guy who had it before me just disconnected the sensor in the motor. There are two blue lines that come from the oil resevior. If you unplug these and fire her up with no alarm, you know that's the problem. Just make sure you eyeball the oil level if you choose not to fix the sensor.

Re: 1999 25 mercury 2-stroke alarm

No this is not oil injected motor.

Re: 1999 25 mercury 2-stroke alarm

Never seen a alarm on a 25hp, 2-stroke but I do know there is a port for a temp sensor on the top of the water jacket on the head. Look at it and see if there if there are wires going to little sensor on the head water jacket. If so then you have a overheat alarm. The only thing that would trigger a alarm is either the thermostat not working correctly or the water pump not pumping enough water. I think the thermostat opens at 120 degrees which means at idle you should'nt have a steady stream of water out the pee hole....and the motor should be running around 120 degrees all the time. If you do replace the thermostat...be very careful removing the bolts in the housing, they are very thin and break very easily if they are corroded. The waterpump is very easy to change, and if you havnt relaced it in few years, then it's time for a service.

Re: 1999 25 mercury 2-stroke alarm

Thanks, i will check it out.

Re: 1999 25 mercury 2-stroke alarm

Just wondering if when you droped the lower unit how did the shift rod come out?

Re: 1999 25 mercury 2-stroke alarm

Look behind the carb under the starter, you will see a cam at the bottom of the motor, thats where it is. At the front of the cam is a tab, get a long flat blade screw driver and lift up on the tab, flip it up and pull it out. Thats frees the shift rod. I usually remove the starter to make it easier to get to mine. It takes like a minute to remove the starter if that.