'91 Merc 200 oil injection problem

[wiliermdb]

My brother had his boat out on Sunday for about 20- 25 minutes when the alarm sounded for the oil system. He stated it lost power and he shut it down for awhile to inspect the system. He had an issue with it about 2 1/2 months ago. Found the tank on top of the motor had a cracked cap.
He replaced the cap and all the hoses for good measure. Has not had an issue with it for probably 25- 30 hours of use.

Tank in boat is full. Tank on motor is full. Motor was still smoking after alarm and again after he let it sit. Obviously still getting oil.

Any suggestions from our master mechanics here?  Again, it's a 1991 Merc 200 OB.

Thanks,

Marc

[thedeuceman]

not a master mech... but
i just helped a friend out with a smaller merc on his pontoon
it was always sounding the alarm, i found a few posts about troubleshooting it, turned out to be a bad oil level sensor.
as i recall the switch closes when the level is low so i disconnected it to keep the alarm off till he could order a new float

[Rich_V174SS]

If I remember right there's also a sensor on the oil pump to sense shaft rotation. If there's a failure of the drive shaft operating the oil pump you'll also get an alarm. The shaft is driven by a worm gear which is part of the main crank shaft inside the engine and were often made of plastic. If the gear is broken you'll get intermittent and sporadic operation of the oil pump. When that happens you switch to pre-mixing your fuel and oil and disconnect the oil warning system, leaving the overheat sensor intact.

[terry]

when i bought my boat i had a problem like that.took it out and would lose power after 5-10min of running.(MY BOAT HAS THE LIGHTS THAT GO FROM RED TO GREEN WHEN YOU HAVE A OIL TANK LOW OR PROBLEM- OR COOLING PROBLEM)i replaced the thermostats,oil sending unit in main tank and motor(not cheap at all)still had bell going off.heads would get real hot to the touch-every outboard i have owned i have been able to run it on the muff and place my hand on the heads and they would be warm to were i would not have to remove my hand for a while.i ended up takeing it in and the found the brass cooling tube from the lower to the head had a crack makeing my engine overheat.you should be able to run the boat on muffs and see if you can get the buzzer to go off and remove the red wire from the main oil tank and see if the buzzer goes off after removeing,same with oil tank on motor should be on oil cap top on tank. do one at a time.if buzzer goes out on either the sending unit is bad.if your buzzer still goes off you may have a cooling problem.

[Rich_V174SS]

On the Merc in question oil warnings beep, overheat alarm is a constant alarm. You should also get the tell-tale "beep-beep-beep" when the key is turned on to indicate the warning system is functioning correctly. If you don't get that you may need a new oil warning module.

[Retro Performance]

 THE OVERHEAT IS CONSTANT TONE....LOW OIL (FROM CAP ON ENGINE MOUNTED TANK) PRODUCES SLOW BEEPING AND ROTATIONAL SENSOR (MAGNETIC PICK UP ON OIL PUMP SHAFT) PRODUCES A RAPID BEEPING, ABOUT TWICE AS FAST AS LOW OIL WARNING....WHICH OF THESE DO YOU BELIEVE IS SOUNDING? SYSTEMS DO RUN THROUGH A WARNING MODULE WHICH WE HAVE SEEN MORE THAN A COUPLE FAIL OVER THE YEARS.

[wiliermdb]

It's sounding a fast Beep-Beep-Beep. Motor stalled while on the hose and the beeping continued. Verified the oil pump is working, thinking it's an issue with the warning module. Any thoughts?

[Rich_V174SS]

Does the module give you the 3 or 4 quick beeps when you turn the key on? If it doesn't then the warning module amy be faulty.

[wiliermdb]

Well, the oil injection alarm is now repaired. It was the sensor in the upper tank. Along with that he had taken it out and it would not go over 2K. So he called the local Master Craft dealer and they referred him to a guy that works out of his home or will come to you. Guy has one hell of a resume' when it comes to working on Merc's and Mercruisers. Found that only one side of the motor had spark. Bad box on one side. Replaced that, all fuel lines under the cowl and the sensor in the tank. Also checked his oil pump for the proper flow and is pumping perfectly. All the parts and labor for $369. Not bad at all. Only took him 4 days with some parts that had to be ordered.

Brother will take it back in December to have the pivot bushings replaced and the water pump replaced.

We took it out on Sunday and that 200 will yank you out the water before you have time to say "ready!!"

Thanks for all the suggestions and info on here.

[bellj]

When I got my Mercury 200, the previous owner had already converted it to premix, but he included the parts he took off.

I toyed around with converting it back, but the more research I did, the more that I noticed how much was written about failures and why the extra hassle along with idle fowling of premix was worth converting away from injection on the old systems with the plastic drive gear.

There was one highly recommended alternative suggestion, which I seriously considered if I wouldn't have to revise a portion of the cover because certain years where narrower, plus I used some of the critical space to install an electric primer off of a Sportjet engine to eliminate hand priming issues...besides, in the end I have gotten used to the premix again and worry about injection issues less.

So just for your consideration maybe some time in the future, the mentioned alternative was for an electric/electronic motor mixing system which is manufactured by a former Mercury person. Everything I looked up speaks very highly of his system as well as his knowledge, and he seems very attentive and hands on - he responded to my email about why my motor's year wasn't in the list in about 15-20 minutes and told me how to modify the cover if I wanted it to fit because that was the only obstacle for it working on that year motor. His website is: www.marinesolutionswi.com

Good luck.