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Long steady beep 1999 Mercury 115

T

Tpoliti

New member
Took the boat out yesterday, first trip of the year. Went about 2-3 miles and got a long steady beep alarm. Shut it down, started it up a minute or so later, went a few more minutes same thing. Turned around and headed back, did stop for lunch on the way.

According to google this is likely an oil or overheating issue. How do I diagnose which? I can replace the thermostat, it was done beginning of last season. I normally get 2-3 years of use before changing. Trying to avoid throwing money into the wrong parts.

It’s a 115 Merc, Saltwater series, 2 stroke, carbureted (2+2) so I’m told. I did replace the check valve on the oil tank this year, not sure if that could have created an issue.

Any thoughts?
 
If your 115 has a "modulation module" the low oil level, if it's functioning, will cause an intermittent 1-0-1-0- type of alarm. Over temp is solid. With no modulator module both will give you a solid alarm.

The engine has a thermostat and a poppet valve. The thermostat controls temperatures up to 2500 RPM (manual number). The water pressure above that speed forces the poppet off its rest and allows a greater amount of water to flow through the block at the higher RPMs.

First off, on the rear of the block embedded in the water jacket (spark plugs stick through it} is the OT sensor and is easily identified by a tan wire connected to it. Follow the wire to the wiring harness and unplug it. See if you still have the problem....if so, it's oil level, if not it's a temp problem.

If temp operate in both areas mentioned and determine which one causes the alarm......I bought a boat and the thermostat wasn't opening. By the time I got out of the "no wake" zone the alarm had sounded......out of sheer luck I firewall the throttle, got on plane and a few seconds later the alarm quit.....OK fine.....slowed back down and the alarm returned....easy fix.....new thermostat. and changed the poppet while I was there as both are under the same cover.

If your magnet falls off your level indicator in your oil tank you will get an oil level low fail alarm. The light blue/white stripe pair of wires is the connection for this sensor connection to the engine wiring harness. If it is sounding, pull one of those wires out of the harness and if the noise stops, this is your problem.

Having a good pee stream doesn't tell you diddly about the circuits mentioned above......the pee is plumbed off the exhaust manifold cooling water loop which is not controlled by the those circuits....since is cools exhaust, if the engine is running its circulating water. If you have a good solid stream at idle and a strong stream up around 3000 or so, your impeller is "probably" OK.

This will give you something to work on and can probably keep you out of the repair shop. Regardless, if you haven't replaced your impeller in the water pump in awhile, now would be a good time to do that.
 
Texasmark said:
If your 115 has a "modulation module" the low oil level, if it's functioning, will cause an intermittent 1-0-1-0- type of alarm. Over temp is solid. With no modulator module both will give you a solid alarm.

The engine has a thermostat and a poppet valve. The thermostat controls temperatures up to 2500 RPM (manual number). The water pressure above that speed forces the poppet off its rest and allows a greater amount of water to flow through the block at the higher RPMs.

First off, on the rear of the block embedded in the water jacket (spark plugs stick through it} is the OT sensor and is easily identified by a tan wire connected to it. Follow the wire to the wiring harness and unplug it. See if you still have the problem....if so, it's oil level, if not it's a temp problem.

If temp operate in both areas mentioned and determine which one causes the alarm......I bought a boat and the thermostat wasn't opening. By the time I got out of the "no wake" zone the alarm had sounded......out of sheer luck I firewall the throttle, got on plane and a few seconds later the alarm quit.....OK fine.....slowed back down and the alarm returned....easy fix.....new thermostat. and changed the poppet while I was there as both are under the same cover.

If your magnet falls off your level indicator in your oil tank you will get an oil level low fail alarm. The light blue/white stripe pair of wires is the connection for this sensor connection to the engine wiring harness. If it is sounding, pull one of those wires out of the harness and if the noise stops, this is your problem.

Having a good pee stream doesn't tell you diddly about the circuits mentioned above......the pee is plumbed off the exhaust manifold cooling water loop which is not controlled by the those circuits....since is cools exhaust, if the engine is running its circulating water. If you have a good solid stream at idle and a strong stream up around 3000 or so, your impeller is "probably" OK.

This will give you something to work on and can probably keep you out of the repair shop. Regardless, if you haven't replaced your impeller in the water pump in awhile, now would be a good time to do that.
Click to expand...
Thank you, I’m going to need to read through this a few times. The impeller and thermostat were changed prior to last season. I’m only getting the alarm at around 4500-4800 rpm after running a bit. It’s a solid alarm, not the on/off low oil alarm, I had just added oil prior to taking the boat out. I came back at 3000 rpm and no alarm at all.
 
Tpoliti said:
Thank you, I’m going to need to read through this a few times. The impeller and thermostat were changed prior to last season. I’m only getting the alarm at around 4500-4800 rpm after running a bit. It’s a solid alarm, not the on/off low oil alarm, I had just added oil prior to taking the boat out. I came back at 3000 rpm and no alarm at all.
Click to expand...
I'll "throw my hat in the ring" for a defective poppet.....probably corroded to some extent so that it partially works, but doesn't open all the way. On having the Tstat replaced with the impeller, but not the poppet too, since they are under the same cover, bad call for whomever did your engine work!
 
Tpoliti said:
Took the boat out yesterday, first trip of the year. Went about 2-3 miles and got a long steady beep alarm. Shut it down, started it up a minute or so later, went a few more minutes same thing. Turned around and headed back, did stop for lunch on the way.

According to google this is likely an oil or overheating issue. How do I diagnose which? I can replace the thermostat, it was done beginning of last season. I normally get 2-3 years of use before changing. Trying to avoid throwing money into the wrong parts.

It’s a 115 Merc, Saltwater series, 2 stroke, carbureted (2+2) so I’m told. I did replace the check valve on the oil tank this year, not sure if that could have created an issue.

Any thoughts?
Click to expand...
Assuming this has a sensor in the oil reservoir, did you check that?
 
jimn said:
Assuming this has a sensor in the oil reservoir, did you check that?
Click to expand...
My understanding of the oil level sense circuit is that low oil is low oil....matters not how long engine has been running! Turn the key on you have it, turn it off and it goes away.....not what's happening here.

OT sensor is heat driven and heat builds as engine runs! The fact that the problem occurs as it does, indicates good coolant circulation but not good enough to support the higher engine RPMs! Course, corrosion buildup within the coolant passages could be the problem too. Poppet is a quick, basically easy, low cost, fix. Good place to start. Next would be to remove the rear block water jacket cover and have a look at the block's water passages.
 
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