150 HP Merc XR6. For about a year now, my low oil beeper has been going off. First it would only go off when running rough water intermittently. I'd stop and pull the cowling off, plenty of oil in the reservoir. Yesterday it started beeping and would not cut off. Pulled the cowling off several times and had plenty of oil. Float seems to be free and able to sense oil level. What do I need consider looking at first? Or should I just go ahead and take it to my mechanic?

Although you say the float seems to be free, I'd say the sensor (float) in the reserve tank is still the culprit. Try to duplicate the problem manually by moving the float on the sensor with key switch on.

Semi-bad news. Mine did that. Then went into preservation mode, where it would not go above idle RPM. Took it to the mechanic.

You didn't say what year it was. Mine is a 1986 Mariner 150 Mag.

Mechanic said that the oil pump is driven by a drive shaft that runs off of a worm gear meshing with a Fiber Gear on the Crank Shaft. It is common for the fiber gear deep in the engine to slowly begin to shear off. The check is to take the oil pump off, and hold the shaft stationary with a large screwdriver, while having someone turn over the motor (remove plug wires). It might take some force, but if you can hold the oil pump drive shaft stationary while the motor is turning over, that is your issue. Don't spend the money on a new oil pump like I did.

Two fixes:

1.) Spend HUNDREDS of $$$ having the motor torn down to the crankshaft, to replace that fiber gear with another one.

or

2.) Have the mechanic remove the self oiling system altogether, and start mixing your oil and gas when you fill er up. That's what I did. Its just slightly inconvenient, but a whole lot cheaper. Plus, I KNOW the motor is getting oil.

Sorry for the bad news, but it's not really that bad. Maybe you'll have luck finding a float or something, but that is what happened to me.

I had a 96 Johnson 135 that after looking at my third oil pump replacement, just had it removed and pre mixed the oil and gas. Both other times, it had the same symptoms you are describing. I sold it last year and bought a boat with a 4 stroke Yamaha to push it with. No more mixing, but Yamaha Ring Free is over $60 for 64 oz. Good news, I average just 1 oz a trip. I got 15 more hp with the new-to-me boat and use 1/2 the gas than my old 2 stroke.

2006 model. I will be calling my mechanic shortly.

After talking with Chris at Classic Fiberglass, he recommended trying to make sure everything was sealed up good and that the float could be the problem still. I manually topped off the onboard reservoir and cleaned the cap of the tank in the hull real well. That fixed my problem, thought I saw a little grime on the sealer plate. Thanks Chris!!

I had to replace the oil reservoir on my 2004 Optimax 225 last year. There is a washer(?) that is adhered to the float in the reservoir. It is common for the two to separate and cause the low oil alarm. Watched several YouTube vids on this problem/repair.

Sounds like a bad float sensor, try a jumper wire and see if it quits. You have to buy the complete reservoir on mine because they don’t sell the float sensor separately.