1988 90hp low oil level sensor

[Schnidly]

Hi All, I own a 1988 90hp mercury outboard, OB302485 serial number. My low oil level sensor alarm went off, beep, beep, beep. I filled up the oil tank, there was about a quart left in it, but the alarm still beeps when I turn the key on. I checked the continuity through the sensor on the two white wires coming out of it and I have continuity with the tank full. Would this mean the sensor is bad? If so, can someone give me the correct part number for the level sensor switch and tell me how to remove the old one from the bottom of the tank? PLEASE HELP! Also, how does one check the warning module even though I dont think it is the problem. THANK YOU!

 

[emckelvy]

Re: 1988 90hp low oil level sensor

You can look up parts for your motor here, just find your model and click on the correct serial # range:

http://www.mercruiserparts.com/SelectModelType3.asp?class_id=2

The switch is a reed-type which is held in place by a screw and fits in a recess in the bottom of the tank. It doesn't physically sit in the oil.

However, I'd bet you that the switch is not the problem. There's a magnet glued to the bottom of the float, inside the tank, and this is what trips the switch on low level.

After some years the glue fails, sending the magnet to the bottom of the tank forever and triggering the alarm constantly.

You can check the alarm module by unplugging the switch. I bet it stops!

You can also check to see if the switch actually works by removing the oil tank and turning it upside down. The magnet should fall to the top of the tank along with the float, causing the switch to open.

Bad thing about this is, the tank and float assy are sold as a unit, so you have to buy a new tank to fix the problem. Wonderful !!!!

HTH & let us know what you find.............ed

 

[achris]

Re: 1988 90hp low oil level sensor

As stated above, the whole oil tank...

Part number : 1255-8627A6

Chris.........

 

[Schnidly]

Re: 1988 90hp low oil level sensor

So after I disconnected the two white wires from the warning module light blue wires and checked the continuity through the low oil level switch mounted in the bottom of the oil tank and got continuity through the switch indicating a bad switch this is not the problem? I thought the switch came as an assembly? There is one screw holding this switch in place in the bottom of the tank. I know I have to drain the oil out of the tank to remove this switch but isnt the magnet and switch all one assembly?

 

[Schnidly]

Re: 1988 90hp low oil level sensor

Hi Again,

I removed the sensor from the bottom of the oil tank, I checked continuity and I had none which is what I suspected so the sensor itself is good. It is just a 2-3 inch long rubber coated rod with two wires coming out of it. My question is if the magnet came off and fell to the bottom of the oil tank why cant I fish it out with a magnet? I did try this and could not locate it??? Im trying tot visualize how this tank looks on the inside? Can someone help me? Also, does this mean I have to replace the entire oil tank just to get the magnet??? How does the magnet mount on the inside of the tank, anyone have any diagrams how this tank is constructed? THANKS GUYS and GALS!

 

[achris]

Re: 1988 90hp low oil level sensor

The magnet WAS glued to the bottom of the float which is on a spindle. The spindle is hollow, that's where the reed switch (the one you removed and tested) is normally housed...

No you can't remove the float and re-glue the magnet... Trust me, I've tried...

Chris..........

 

[Schnidly]

Re: 1988 90hp low oil level sensor

Hi All,

Got the tank out with a little finnesse! I was unable to get one of the bolts out of the bottom that holds the bottom boot and the bottom of the oil tank in place. I had to work the top left side of the tank out of the rubber mount it is seated in and pry it out. I could have taken off the cowling that covers the carbueretors, but I did not want to take that off. Aftert getting the tank out I noticed that the magnet was still in tact in the bottom of my tank, the magnet was not moving freely however up and down the hollow shaft. I rehooked up the leads to the reed switch, flipped the tank over and the alarm stopped. Id flip it back up right and Id get the alarm again until I flipped the tank over again! My magnet was sticking and Im just going to replace the tank all together even though the magnet did not come off. Theres like a push on retaining clip that holds the magnet onto the inside shaft, that was still intact and in place! Magnet was just sticking! Can anyone tell me if tygon tubing 1/4" in diameter will work for the new oil lines from the tank to the oil pump and sight tubing for the level inside the tank??? Not sure if this is some special clear tubing or not???

 

[Nauset #37766]

Re: 1988 90hp low oil level sensor

You need to use clear tubing for the lines from the tank to the pump and from the pump to the fuel pump in order to make certain that there are no air bubbles in the lines when you bleed them.
Bill