1972 Johnson 100hp wiring harness

[mano]

First off, I'm not positive of the year of this unit. It's a model 100ESL72R. Is it a 1972, and is it electric shift?

This is not mounted on a boat and has been stored for 5-6 years, and I'm having trouble figuring out the wiring from the harness that leads to the controls. I have a Clymers shop manual and think I have figured out most of the wiring, except one larger gauge red wire.

Here's what there is and what I have found on Clymers.

Red- Unknown (this is a larger gauge wire than the rest)

green - shift selector
blue - shift selector
purple/green -shift selector
black - control housing ground
White - ignition (S)
purple/white - ignition (battery)
purple - ignition (ignition)
tan - horn (for temp switch)
grey - tach lead

Does this sound right? What is the larger red wire for?

Before mounting this on a boat I just want to hear it run. Can I just hook up the 3 ignition wires. I do have the ignition switch as well as the shift control.

Thanks in advance for any help.

 

[tashasdaddy]

Re: 1972 Johnson 100hp wiring harness

red is the positive from the motor to power the control.

Hydro Electric Shift)
(J. Reeves)

The shifting setup of the lower unit is what's called a "Hydro Electric Shift", which is quite complex consisting of voltage being applied to solenoids in the lower unit which in turn change oil passages via a oil pump that supplies various pressure on a spring loaded shifter dog. The wires leading to the lower unit (at the powerhead) are "Green" and "Blue". The engine must be running or cranking over in order to shift out of forward gear.

You CAN NOT use HI VIS lube in that lower unit. You MUST USE what OMC calls "Premium Blend" lube, commonly called "Type C". (A thinner lube)

In neutral, you need 12v to the "Green" wire.
In reverse, you need 12v to both wires, the "Green" one and the "Blue" one.
In forward, there should be no voltage to either wire. (The spring loaded shifter dog forces the unit into forward gear)

To check the lower unit for proper shifting to make sure you have no trouble there, remove the spark plugs to avoid problems and to allow a higher cranking speed.

This next step eliminates the actual shift switch in case problems may exist there.... Disconnect the blue & green wires at the knife connectors (the rubber insulated boots) leading to the lower unit at the powerhead, then using jumpers, take voltage direct from the starter solenoid to apply voltage to the "Green" wire for neutral, then both wires 'Green" & "Blue" for reverse (Remember the engine must be cranking over in order to shift).
With no voltage applied, the unit should be in forward. No need for a ground jumper... the lower unit's already grounded. You may crank the engine with the key switch or by energizing the starter solenoid with a jumper wire.

 

[mano]

Re: 1972 Johnson 100hp wiring harness

Thanks for your time and help!!