Merc 115HP ELPTO Two stroke Low Oil Alarm issue

[rcadille]

Merc 115HP ELPTO Two stroke Low Oil Alarm issue Serial No. 1B023978 Trying to determine which item is bad. Low oil sensor, Powerhead Temp/Engine Overheat sensor, Warning Alarm Module or ???
Originally the alarm horn did not work and I accidently ran the SilverQuick oil out - engine stopped, I refilled reservoir and all is OK except the alarm horn near the starter key did not buzz intermittent or steady alarm. Troubleshot the alarm horn and it in very dead. so I Bought an off brand 12V Alarm with Light and replace the it (Purple and tan/blue wires near starter key).
Now the horn stays "on" Steady as soon as key is turned to on. Merc Service Manual for this engine, page 3C-16 has a Troubleshooting Chart. Went through the "Steady - always On" horn area and it is not making any sense. Here's why: It says to disconnect Engine overheat sensor BLACK wire and try agaion. It is a tan/blue wire, not black. Disconnected tan/blue, still Steady ON horn. I have the Warning Module unbolted from engine (Module P/N 821889) it has three wires of four in use, black, red, tan connected to wiring harness, black, red, tan. Also a black/yellow wire that it not used.
QUESTION: is it possible to check the operation of this warning module?
QUESTION: What if anything do you recommend -- need some advice? Next wire checks?

Also - I have not checked the blue wires on low oil float because they are very hard to get to without removing the oil reservoir.

 

[Kat Daddy]

What you may find is the the small magnet has separated from the float inside your 2 stroke oil reserve. It looks complicated to repair but really isn't. There are several YouTube postings that will show you what to do.
Will add a couple of tricks I learned in fixing mine.
1. be sure to put a paper or cloth towel under the tank to catch any bolts that my drop 2. siphon as much of the oil from the tank before removing
3. There is a split ring holding the float on the sensor tube, I took a welding rod and hammered down the bare metal end, then filed a hook to enable to catch the split grove and remove the ring, works much better than the screw driver trick mentioned on Y-tube. 4. I used JB Weld on the magnet, it has not cured yet, but the instruction says it is good with any petroleum product.

To check to make sure the sensor is still working properly, turn your key on (do not start the motor) which the alarm should not go off, then place a magnet by the sensor, if it goes off, it is still good.

Warning, they are not making these plastic reservoirs anymore for the older motors, or at least that is what I am being told, and could not find any on the Mercury website. Boat dealer said he couldn't find any either. I got lucky and found one on E-Bay. If you find one, might be good to have as a back up if your repair job goes South.

Hope this helped