View Full Version : Low oil Warning

July 10th, 2004, 10:21 PM
Was going down the lake the other day and my low oil warning began beeping on my Mariner 90. Shut down thinking I needed to add oil but my oil resevoir was full. Trailered my boat and went to the house. Got out the maintenance manual and it says to disconnect the two wires going to the low oil sensor and check for continuity in the magnetic float and sensor circuit. Well I have continuity and this indicates a bad magnetic float and/or sensor. The float and magnet is inside the tank and unaccessible. The sensor inserts in the bottom of the tank and the float/magnet moves up and down around the sensor. Thing is when I removed the tank and emptied the oil out I still had continuity through the switch/sensor which is correct. But I reasoned if I turn the tank upside down then the float would fall to the full oil position and if still had continuity through the switch then I would agree with manual that either senor is bad or float/magnet is bad. But it breaks the circuit as it should when I turn the tank upside down. When I turn the tank back upright I have continuity as I should, but when I fill the tank with oil I have continuity through the switch when I shouldnt. Any ideas before I order a new oil tank and sensor.....RL

July 12th, 2004, 09:54 PM
some guesses from someone who has never worked on the sensor in question.
When you fill the tank can you see if the float is rising?
Could the float 2 parts? a floaty part and a connection/magnet part that has separated from the float?

July 13th, 2004, 01:14 AM
Joed thanks for your reply as it turns out you are absolutely right the magnet part of the float came unglued from the bottom of the float. The float was rising as you suggested but not the magnet (the magnet looks just like a washer glued to the bottom of the float). Now I find that to be questionable engineering, why glue a magnet to the bottom of the float when it is going to be submersed in an oil environment. Seems to me put the magnet on the top side of the float. Anyway you cant just replace the float/magnet you have to replace the entire oil tank. However I read your reply before ordering a new tank and that got me thinking and sure enough you were right. Problem is the float is prevented from replacement by a push nut. So somehow you would have to reach about 10 inches down through a 1 3/4 hole remove the push nut and replace the float/magnet. Figured that was probably doable with the right tool. So called my boat guy and wouldnt you know they dont sell just the float/magnet have to get an entire tank. Geeeeezz ....so I'm out 50.00 bucks which isnt to bad. Supposed to come in tomorrow and pretty easy to replace just have to remember to bleed the oil pump before running the boat. Thanks though because your thoughts gave me a fighting chance at a rather cheap repair. Just as they say "you win some and you lose some" . Check back on this post over the next week and I will have a picture of the float posted. Going to cut that section of the tank out on my band saw.......RL

July 13th, 2004, 09:06 PM
Sometimes you get luckly and look like genius. Sometimes you look like the south end of a north facing horse.