Mercury 135-HP V6 Broken Plastic Gear For Oil Mixing Pump

[Scarab]

I recently bought a used -[2000 --please always use four digits for model year information] Mercury 135-HP engine with just 107-hours. After a complete service and just seven hour of enjoyment the [aural alert alarm] started to sound. I have checked the thermostat, and the [aural alert] for malfunctioning. The mechanic said it is the "inner gear failure" which has broken and needs to be replaced which will end up very costly as the motor will need to be teared down. Any ideas [about alternative repairs] will be welcomed. Many thanks.

[floater]

[Infers that the problem is due to failure of the plastic drive gear for the oil mixing pump, and says it is a] common problem with these Mercury motors. You can switch to mixing your gas and oil and save on the rebuild. On my engine (200-HP} [the drive shaft] is aluminum, accessible, [being driven by] a plastic, inaccessible, gear. Designed to fail and make them money.

[Scarab]

Do I need to terminate and disconnect the oil injection system? And from then on I just add 2% of oil in gas ? Will that affect the life of the engine? And what about the beeper sound? How do I switch it off?

[jimh]

Almost no owner of one of these Mercury engines with the oil mixing pump being driven by a plastic gear has ever actually spent the more-than-one-thousand dollars in repairs to replace the failed plastic gear with another plastic gear that will eventually also fail. My local dealer has seen many Mercury engines fail like this and no customer has ever gone with the repair; there are two solutions.

--begin to pre-mix two-cycle oil into the gasoline fuel. Remove most all of the existing oil mixing system. The usual ratio of oil to gasoline is 1:49. Cover the hole leading to the crankcase where the old pump drive was located.

--install a aftermarket replacement pump system; see below.

Because of the high cost of repair of a failure of the plastic drive gear in the Mercury oil injection system, an alternative after-market solution has been developed. It replaces the OEM oil mixing pump with an electrically operated pump. The cost of a gear replacement is estimated at $1,200. The cost of retrofitting an electrically operated pump is estimated at $575.

For more information on this solution, see:

Marine Solutions (Wisconsin)
THEY USED TO HAVE THIS DOMAIN BUT IT IS NO LONGER WORKING: marinesolutionswi.com
USE THE INTERNET WAYBACK MACHINE TO LOOK FOR OLD EXAMPLE OF THEIR PRODUCTS

https://web.archive.org/web/20150217204840/http://www.marinesolutionswi.com/

They have retrofit kits available for Mercury V6 outboards:

--135 to 200-HP, 1989 through 1999

--200 to 225-HP, 1995 through 2001 3-liter

The manufacturer of this retrofit comes with some credentials. Robert Kachelek, president of Marine Solutions, was formerly the director of Outboard Service for Mercury Marine.

Also see these older threads on this topic:

http://continuouswave.com/ubb/Forum3/HTML/010414.html

http://continuouswave.com/ubb/Forum3/HTML/016744.html

Also see my REFERENCE SECTION article which describes the Mercury oil system in detail:

http://continuouswave.com/whaler/refere ... ction.html

[jimh]

To go to pre-mixing you have to modify the oil system to remove the components no longer useful, i.e., the various hoses and T-connections in the fuel flow system where oil would be flowing from the reservoir tank to the mixing pump, the mixing pump itself, and any other components no longer needed.

You have to modify the alarm system to prevent the oil motion sensor from causing an alarm.

You have to modify the alarm system to prevent the lack of oil in the reservoir and the float switch from causing an alarm.

Generally in an alarm system the sensors are just switches. You can replace the switches with just an open circuit or a closed circuit, according to how the alarm system works and which is the NORMAL condition. Please let us know what you find is the normal circuit condition for the no-alarm state.

The MOTION SENSOR module is unknown to me, so I don't know exactly how you eliminate the alarm signal from it. It might be just a switch or might be something more exotic like a pulse stream. Experiment and let us know if you succeed in silencing the alarm.

[jimh]

The engine will run on pre-mixed oil:gasoline with the failed pump. I don't think there is any downside to this. The only problem that may occur is you will forget to add oil to the fuel and the engine will be damaged. Just don't forget to add oil.

[Scarab]

Many thanks Jim for all the useful info update!

[Scarab]

One last question Jim, I have operated the engine around 2.500-3.000 rpm' s for about 10-15 min in order to get ashore from the time the buzzer started, would that have an effect on the engine cylinders?

[jimh]

The effect of running the engine without oil being mixed into the fuel is probably proportional to engine speed and time. Less speed and less time is better.

[pcrussell50]

I have nothing to add to Jim's very complete answer except to add a data point by saying​ that I have the 150hp version of this engine and it already had the oil system removed when I bought it in 2014. It has been working very well with premixing oil into the gas.

-Peter