1998 Mercury 150 low oil alarm

ntarver0568

Cadet
Joined
Aug 4, 2008
Messages
24
My boat has been sitting up for approximately 3 months, and I just went to run it today and the alarm starts beeping like crazy as soon as I start it. I poured more oil in the reservoir and still, the same. If I remove the cap (where the float sensor is) from the reservoir under the cowling and turn it horizontal the alarm stops. The oil reservoir on the outboard is completely full of oil.
 

fisherman81654

Petty Officer 2nd Class
Joined
Sep 5, 2011
Messages
135
Re: 1998 Mercury 150 low oil alarm

My boat has been sitting up for approximately 3 months, and I just went to run it today and the alarm starts beeping like crazy as soon as I start it. I poured more oil in the reservoir and still, the same. If I remove the cap (where the float sensor is) from the reservoir under the cowling and turn it horizontal the alarm stops. The oil reservoir on the outboard is completely full of oil.
It sounds as tho you have a short in the wireing,I think there are only two wires in the harness,they must be touching when the alarm goes off.
Take a close look at both wires near the cap and make sure that they do not touch.
I f you decide to get a new cap and wireing,twist the cap counter clockwise a few times, before you screw on the cap clockwise,that way it will not put stress on the harness.
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Re: 1998 Mercury 150 low oil alarm

Sounds like float is sticking or not floating....
 

ntarver0568

Cadet
Joined
Aug 4, 2008
Messages
24
Re: 1998 Mercury 150 low oil alarm

Okay, upon further testing, if I take the float out and push it all the way down it stops beeping. When I lift it
back up it starts again. It's working backwards.
 

ntarver0568

Cadet
Joined
Aug 4, 2008
Messages
24
Re: 1998 Mercury 150 low oil alarm

It sounds as tho you have a short in the wireing,I think there are only two wires in the harness,they must be touching when the alarm goes off.
Take a close look at both wires near the cap and make sure that they do not touch.
I f you decide to get a new cap and wireing,twist the cap counter clockwise a few times, before you screw on the cap clockwise,that way it will not put stress on the harness.

There are 2 wires, a blue and a black. I have checked both for shorts and there are none that are visible. The black wire grounds to the block. I removed the screw and sanded the area on the block to ensure good contact. I traced the blue wire to a sealed box with several other wires going into it. I just don't understand why it seems to be working backwards. Thanks for all of the help! I have read in other forums about the magnet falling off, but I'm not sure where that is located or what it looked like with it on there before. I haven't read any forum with a solution to this yet, but it seems to be a common problem.
 

Schnidly

Petty Officer 2nd Class
Joined
Aug 12, 2001
Messages
143
Re: 1998 Mercury 150 low oil alarm

I had the same problem on a 1988 Mercury 90hp. Mine ended up being the magnet that is glued on the float fell off and there was NO WAY other than purchasing a new oil reservoir tank for $35. I was surprised it was only $35 being a Mercury and NO parts cheap! Anyways, my problem was the same as yours and it was the magnet seperating from the float.
 

ntarver0568

Cadet
Joined
Aug 4, 2008
Messages
24
Re: 1998 Mercury 150 low oil alarm

I had the same problem on a 1988 Mercury 90hp. Mine ended up being the magnet that is glued on the float fell off and there was NO WAY other than purchasing a new oil reservoir tank for $35. I was surprised it was only $35 being a Mercury and NO parts cheap! Anyways, my problem was the same as yours and it was the magnet seperating from the float.

Changed the float, still working backwards. The module is $250 and as far as I can tell that's the only other thing that it could be. Just want to make sure before I waste more money. Any suggestions?
 

fisherman81654

Petty Officer 2nd Class
Joined
Sep 5, 2011
Messages
135
Re: 1998 Mercury 150 low oil alarm

Changed the float, still working backwards. The module is $250 and as far as I can tell that's the only other thing that it could be. Just want to make sure before I waste more money. Any suggestions?
Other than making sure that the module has a good clean ground,which it probaly does,looks like the module is the problem.
It wouldn't hurt to run a temporary ground wire from the starting battery negitive terminal to the ground area of the module.
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: 1998 Mercury 150 low oil alarm

The tank float on the IN-line motors is the one that the magnet falls off the float, the V-6 motors tank cap is totally different style and do not have the magnet.

The V-6 motor mounted tank MUST BE over-filled, as in loosen the cap with the motor running at an idle to allow oil to transfer from the main tank to the motor tank until it actually starts leaking from over-filling, THEN tighten the cap snugly.

The alarm module is triggered by this cap/switch, it can also be triggered by sensing any difference between the oil pump rotation sensor and the ignition pulse monitored off of one of the ignition coils, usually #4.

Test by disconnecting the oil cap wires, start the motor, does it alarm now?

If no change, reconnect the cap wires and disconnect both the pump rotation sensor and the green ignition wire coming from one of the ignition coils. Start the motor, does it alarm now?
 

ntarver0568

Cadet
Joined
Aug 4, 2008
Messages
24
Re: 1998 Mercury 150 low oil alarm

The tank float on the IN-line motors is the one that the magnet falls off the float, the V-6 motors tank cap is totally different style and do not have the magnet.

The V-6 motor mounted tank MUST BE over-filled, as in loosen the cap with the motor running at an idle to allow oil to transfer from the main tank to the motor tank until it actually starts leaking from over-filling, THEN tighten the cap snugly.

The alarm module is triggered by this cap/switch, it can also be triggered by sensing any difference between the oil pump rotation sensor and the ignition pulse monitored off of one of the ignition coils, usually #4.

Test by disconnecting the oil cap wires, start the motor, does it alarm now?

If no change, reconnect the cap wires and disconnect both the pump rotation sensor and the green ignition wire coming from one of the ignition coils. Start the motor, does it alarm now?

Just saw your replay, after ordering and installing the warning module. I tried the cap with the float first. It is still beeping as soon as it starts. I disconnected the 2 wires from the cap and the alarm is still going off. I'm not exactly sure where the second set of wires you mentioned are located. I don't see an extra wire comming off of any of the ignition coils and not quite sure where the pump rotation sensor is. I tried looking them up on the internet, but my wifi is messing up as usual. Trying to find it on my iPhone is pretty annoying. Thanks for the help!
 
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