Mercury 100 hp 4 cyl warning beep

[mgsolakis]

Today my Mercury 100 hp 4 cyl (I think it’s a 1991) started beeping at the control. It just keeps beeping every second or so. I am assuming it is a low oil warning or over heat warning. The beeping starts as soon as the key is turned to the on position. Does anyone know what that is?

[billw]

It is the oil warning system. Either the oil is low, the level sensor has failed or the module has failed. I can’t begin to try to tell you how to troubleshoot this with my slow typing over the interweb but DO run your engine on a 50:1 premix tank until you get it worked out. It’s been awhile but I probably have a book someplace.

Long live American manufacturing!

[mgsolakis]

Thanks Bill. So I followed Bill suggestion and checked th oil level. The tank is full but I looked at the inside of the tank an I think the something might be up with the float. A black gasket is just dangling from the cap.

[jeff-register]

Not good!

[jerry-ahrens]

Do yourself a favor, and go ahead and change the oil injection check valve while your at it. I believe yours has the 90 degree check valve threaded into the fuel pump. Or some models have the check valve teed into the fuel line, just ahead of the fuel pump. Post a couple of pics of the port side of the motor so we can have a look. [/size]

[mgsolakis]

Thanks for the insight, I will go out a take a few pictures as soon as I get the baby to sleep. One question though, what do you mean by in boat reservoir? As far as I can tell the reservoir under the cowl is the only one. It is 3/4 full.

[mgsolakis]

Here is the side view of the motor. You can see I have topped up the oil well and beeping has continued.

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[jerry-ahrens]

Sorry, 🙂 I was thinking about a V6 motor vs. yours, so disregard what I said about the larger tank inside the boat. Your engine has only one tank, that’s mounted to the powerhead. It will be nearly impossible to get to the float sensor, since it’s all the way at the bottom of the tank . Sorry for the confusion… i will edit my earlier post.
You will need to do a test of the float switch. Look on the bottom side of the oil tank. Find the two wires that are coming from the float switch, inside the tank. Unplug those wires. If the beeping stops, the float switch is defective. The reason for the float switch failure, in most cases, is a defective oil injection check valve. If the check valve sticks, it will allow fuel to gradually migrate up into the oil resevoir. This attacks the float, and causes it to sink. Thus, a steady oil injection warning. I’ll bet that’s what you will find wrong. As I said before, be sure you replace the check valve, located on the other side of the motor.
If you do find a defective float switch, you will need to order a complete oil tank assembly, since the switch is not serviceable. See a Mercury dealer.

[mgsolakis]

Thanks Jerry, the beeping stopped when I disconnected the wire so you were right. So I will order a new assembly and check valve after the long weekend. In the interm is it just a sensor? Or should I double mix oil in the gas as well just in case? Thanks a lot for your help!

[jerry-ahrens]

Be sure not to reuse the old oil that will be dumped out of the tank, since it will most likely be contaminated with gas. If you want to run the motor as is for the time being, I would go ahead and mix the gas 50/1 just in case. It may smoke a little more at idle, but at least you will be protected. After you install the new tank and oil check valve, refill with fresh oil, and your’e good to go. The oil pump drive gear on those inline models are extremely dependable, so I wouldn’t worry to much about that. Sounds like you have it covered!

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