Alarm beeping on mercury efi 150 outboard.

fished a long night running all accessories. Battery was low enough I had to jump across from a trolling motor battery. shortly after starting I started getting a beeping alarm from my warning system. It is a beep ,beep , beep warning. Only ran it back to ramp and loaded up. I have not ran boat since getting home and charging batteries. It was pumping water and full of oil. Could this be a low voltage from battery warning ? Or will that cause a beep, beep, beep? I have never had this happen or ran across it before. It is a 2002 mercury efi 150. It doesn't have any lights on the dash that can show causes. Thanks for any help ideas.

I took the liberty of posting your question on iboats.com.

I'll let you know if we (you) get any answers. Lots of knowledgeable there too.

No answer over at iboats. Sorry, bud, I tried.

Got an answer. Here it is.


The intermittent horn is usually a signal of a problem in the oil injection system. Charge the battery and run the engine on premix fuel and oil to safely check out the problem.

Another answer.

The oil alarm module checks oil level in the motor mounted tank, loosen the oil tank cap slightly, run the motor until the tank fills from the main tank so full that it begins to overflow, tighten the cap. The module also compares the signal from the oil pump rotation sensor to an ignition pulse from one cyl, often #4, when any difference it alarms.

Find the green wire on the module and follow it back to see for sure which cyl coil it connects to, spark test that cyl to ensure it is not an ignition problem.

Definitely add oil to the fuel just in case it is an oiling problem. The excess oil will only cause it to smoke a bit more than normal, rather that than risk hurting the motor.

if you have a float in the tank some times they become saturated and lose their bouyancy, have had it happen 2 times on my mercury (40 hp) not sure about the bigger mtrs, originaly thought it was a bad sensor but it was a bad float, if you have a float you can move it up and down with a peice of cut coat hanger.

I could never figure it out for sure myself. I loosened the cap on the motor oil tank and started the engine with the ears and water on it. The oil did not ease up out of the tank after a minute or so. I shut it down and looked over the lines and other big oil tank. Looked over the oiling system for visible problems with nothing found (couldn't be that easy). I took the boat to my dealer and they called and said it was the oil sending unit. The older you get the more you know as the saying goes, but most knowledge comes with a price tag for sure. Check [URL=https://www.catalogueau.com/australia-post/]Australia Post Catalogue[/URL] and [URL=https://www.catalogueau.com/jaycar/]Jaycar Catalogue[/URL].

This fixed the problem?? I'm having the same problem with mine. Thought it was something with the water pump. Already dropped enough money. Trying to get to the bottom of it. Any help is greatly app. How much was the oil sending unit??