Merc overheating alarm

Hey guys. Got a scare this weekend. Here's a history first that might help. I went to the coast last weekend and put her in Salt water. I did flush it good and hosed the boat down but didn't open the cowling up and stray the inside off. I was fishing ths weekend and drove about 20 minutes to get where I wanted to fish. I didn't stay very,long, maybe 45 minutes but when I cranked the motor, I had a constant BEEEPPPPP going on. i thought it was the oil sensor so I opened up the reserve and added a 1/3 gallon of oil. Welp, it was still going off when I'd turn the key to the on position.
I don't have to crank the motor, just turn the key ON to make the alarm go off. I read today that it's a overheat alarm with a constant beep going on. I had a steady stream of water coming out so it's not the pump. What's ya'll diagnosis? How would you handle the problem.

It's a 2 stroke Merc 125

What year is the motor? Did you recheck it after the motor had cooled down some?

It's on a 2005 Bay boat and yeh, it had sat there for 2 hours as I pulled cranks from one end of Ross Barnett to the other. Turn the key to ON and BEEEPPPPP

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Originally Posted by DonDon

Turn the key to ON and BEEEPPPPP

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Sounds like another saturated float in the oil tank, common question/problem on this board.

A continuous tone on most Mercs is an overheat alarm and has nothing to do with the oil. More than likely, it's a bad temp sensor. Pull the wire off the sensor to isolate to that sensor. If the alarm quits, that tells you it's that sensor indicating a problem. Put in a new sensor and it should fix your problem.

I ainb;t gonna lie. I don;t know squat about motors. HOW will I know the sensor when I see it? I had ran out of oil when this happened, Had someone tell me it had lost suction or something like that and the sensor was messing up now. KNow oil is a beep beep beep but they said with this problem, it'd be a constant beep. Dang, why do I feel like the road runner now. LOL beep beep

http://www.go2marine.com/docs/1/9/8/9/198911F-f.jpg

Usually brass finish screwed into the block with a wire on it. You should be able to read the number and verify that it's the right one before messing with it.

DonDon

There are a couple of situations dealing with the oil system that will give a continuous alarm. If the oil warning module (small black box below starter on right side of engine with 5 wires coming out of it) is bad it will give a continuous alarm or if the oil level float switch inside the oil tank is stuck or bad it will give a continuous alarm. Also the temp sending unit wire (located on the back of engine by the sparkplugs) goes to the oil warning module. If the temp sending unit is bad or the wire (tan w/lt. blue ) is shorted to ground somewhere it will give a continuous alarm. You can remove the tan/light blue wire coming from temp sending unit to the oil warning module, if the alarm stops it's probably a bad temp sending unit if it continues unplug the light blue wires going to the oil sending switch in the oil tank, if the alarm stops you have found the problem. If after unpluging the temp sending unit and the oil sending switch and the alarm still continues it is probably a bad oil warning module.

Good Luck,

Reel Man

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Originally Posted by CatFan

A continuous tone on most Mercs is an overheat alarm and has nothing to do with the oil. More than likely, it's a bad temp sensor. Pull the wire off the sensor to isolate to that sensor. If the alarm quits, that tells you it's that sensor indicating a problem. Put in a new sensor and it should fix your problem.

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I concur with this, shouldn't have anything to do with your oil. This is coming from a Netflix owner as well. And 12 years as a boat mechanic. Check the sensor my friend and let us know.

I had a merc do the same thing and found it to be the oil sensor in the bottom of the resivoir and it produced a constant beep.

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Originally Posted by striperking

I had a merc do the same thing and found it to be the oil sensor in the bottom of the resivoir and it produced a constant beep.

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Had the very same thing on my buddies 50hp Merc. Constant beep led to the float in the oil reservoir. Replaced the tank, good to go. According to Merc the constant beep is overheat, but after checking the sensor it was ok. I guess that doesn't apply to all Merc's?

That's what I had to do ,replace the oil reservoir,solved that problem.From what I understand they can't be fixed.

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Originally Posted by Reel Man

DonDon

There are a couple of situations dealing with the oil system that will give a continuous alarm. If the oil warning module (small black box below starter on right side of engine with 5 wires coming out of it) is bad it will give a continuous alarm or if the oil level float switch inside the oil tank is stuck or bad it will give a continuous alarm. Also the temp sending unit wire (located on the back of engine by the sparkplugs) goes to the oil warning module. If the temp sending unit is bad or the wire (tan w/lt. blue ) is shorted to ground somewhere it will give a continuous alarm. You can remove the tan/light blue wire coming from temp sending unit to the oil warning module, if the alarm stops it's probably a bad temp sending unit if it continues unplug the light blue wires going to the oil sending switch in the oil tank, if the alarm stops you have found the problem. If after unpluging the temp sending unit and the oil sending switch and the alarm still continues it is probably a bad oil warning module.

Good Luck,

Reel Man

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This is the answer you are looking for. It is the diagnostic procedure that I use for customers with that complaint. From past experience, most likely cause is #1 = oil tank sensor. #2 = warning module #3 Haven't seen a bad temp sensor as of yet.

Did you ever figure out what the problem was???