Mercury Outboard: Switching to Pre-mix After Gear Failure

[DaveBaird]

I have a 1997 Mercury135-HP V6 with an oil pump with a stripped plastic drive gear. I have already removed the shaft and magnet from the oil pump and replaced the oil pump housing. What procedure will I follow to bypass the oil pump and run 50:1 pre-mix?

Which color wire is disconnected to stop alarm from oil pump?

What is done with existing oil hoses?

Thank you in advance. I hope to hear some answers from you guys very soon.

[jimh]

For information about the Mercury oil-gasoline mixing system used on their two-stroke-cycle engines, see

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

The article includes a diagram that shows in detail the hose routing and the electrical connections.

If removing the oil mixing system, you would remove the following hoses and seal off their point of connection to the engine:

--crankcase pressure take-off hose

--oil feed hose to fuel pump

The electrical signals related to the oil alarm system appears to be as follows:

--BLUE lead from under-cowling reservoir tank float sensor

--WHITE and BLUE-WHITE from motion sensor

I suspect that these signals can be disconnected and the wires insulated from ground without affecting the alarm system, which would then function to give you only warning of temperature problems. Or, perhaps as suggested below, the two wires from the motion sensor are connected. I can't really say for sure as the precise electrical nature of the alarm system has not been clearly described. The Float Switch lead is most likely a normally-open switch, so leaving it disconnected should be the proper method to disable it. The motion sensor signal may be more complicated because there are two conductors between the sensor and the alarm module. Some experimentation may be necessary to discover the proper method for handling that circuit.

In an earlier article, the following procedure was suggested for removal of the oil mixing system:

--remove oil tank and two lines that come from boat and hook to engine;

--remove the check valve on the side of the engine that the oil tank gets pressure; install a 1/2" pipe plug;

--remove engine mounted oil tank;

--remove the oil gear from engine; the best thing to do is to install the oil gear plug available at local Mercury dealer; installing the oil gear plug prevents a brass bushing from falling out of its desired position

--remove oil warning system boxes and oil gear magnetic pickup from engine;

--if the engine is an EFI engine then you must plug the hole in the bottom of the fuel tank that came from the oil gear; it is a 1/16th pipe thread.

This is where my memory gets foggy, and if anyone can correct me please do.

There is a brown with blue strip (if I remember correctly) that must be relocated on the starboard side electronic panel. what happens is the wire that ran through the oil warning system (that has been removed) is put on the terminal that leads back to the buzzer.

What then happens is that the buzzer that was heard when you first turned the key to the on position doesn't sound any more. But the over heat alarm still sounds when an overheat condition exist.

I recommend you read the earlier discussion about the Mercury oil mixing system, as it contains some anecdotal reports about removing the system. See

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

[DaveBaird]

Can the PURPLE wire from the sensor module be disconnected to stop oil alarm?

[jimh]

The color of the insulation of an electrical conductor can be a clue to its function. See

http://continuouswave.com/whaler/refere ... .html#Merc

In general on outboard engines, all conductors with VIOLET (or sometimes called purple) insulation are associated with the distribution of 12-Volt battery power. Therefore it would be a reasonable assumption that, if you remove the 12-Volt battery power from an electrical or electronic device, then the electronic device that was getting its power from that conductor will cease to function.

[mhannon]

Hello all - still a bit unclear on how to handle the remaining electrical connections between the motion sensor and the electrical sensor (white and blue/white) as well as the two wires going to the oil float. Cap everything off? Or is there something that needs to be done with the white and blue/white wires to fool the old motion sensor buzzer? Thank you!

[A636089]

[T]hat[']s a good question. I was wondering the same thing.

[jimh]

I was wondering the same thing.

Me too.

Why one of you try the various methods recommended in the prior discussions and earlier postings, and report back on the outcome.

Regarding the float switch, I was sure I mentioned this earlier. Let me see if I did. I thought for sure I had mentioned this explicitly.

Heck, I did already discuss the float switch circuit. Here is what I said in an earlier reply to your question:

The Float Switch lead is most likely a normally-open switch, so leaving it disconnected should be the proper method to disable it.

Let me propose this: why don't you disconnect the wire to the float switch from the alarm unit, insulate that wire, and see if your get an alarm?

If you don't get an alarm you can probably conclude the switch circuit in the reservoir level sensor was a normally-open switch, and it closed (to ground, since there seems to be only one conductor in the circuit) to signal an alarm. They we will know from now on how to handle that circuit.

It will be a lot easier for you to test these methods than for me. I don't have a Mercury engine to experiment with, and you do.

[mhannon]

Jimh--thanks for the reply. I see what you mean regarding the float switch; it should be very easy as it is either a NO or NC connection. Easy to test.

The two white and blue/white wires going to the motion sensor are a different story. If the main electrical sensor unit is sending 12-VDC to the motion sensor and looking for a return 5-Volt pulse, how do you trick the electrical sensor unit once the oil pump and motion sensor are no longer connected? There was a reference by an earlier poster that one of the wires had to go to a junction block elsewhere on the motor but I can't determine where they might be referring to.

Thanks again for any input

[jimh]

I really don't have any knowledge of how the motion sensor circuit worked in your Mercury outboard engine. As you surmise, it might be more difficult to suppress the alarm indication if there is a loss of signal returned from the motion sensor and if the motion sensor is creating some sort of pulsing return signal to the alarm unit. My three guesses at a remedy are:

--find a compatible alarm unit from another Mercury outboard engine that does not incorporate the motion sensor, and substitute that alarm unit for the original one;

--dispense with the alarm unit entirely, and just wired the alarm sounder directly to the temperature sensor; I think that temperature sensing is about the only alarm function that remains once you suppress the float switch signal and the motion sensor signal; this could be the simplest solution;

--devise some sort of little circuit to generate the motion sensor pulses; those motion sensor pulses must have been correlated with engine crankshaft speed; you could develop a similar signal by tapping into the AC-side of the alternator windings; this will give you a pulsing DC signal proportional to engine speed; this may have been what was being suggested by the comment to wire the alarm module to some other signal in the outboard engine electrical wiring harness.

[jimh]

To elaborate on my proposal to make your own alarm system for just temperature, you would need a temperature sensor that was just a normally-open switch and closes to chassis when the temperature threshold is reached. This is a common device in outboard engines. Wire the 12-VDC positive to an alarm sounder, and carry the negative circuit of the alarm sounder to the thermostat switch. The alarm will sound when the temperature is above threshold.

[mhannon]

Great suggestion re: focusing on the temperature sender part of the equation. Will probably use that method and scrap the electrical sensor unit altogether.

Thanks Jim!