1972 50 hp Johnson Part Obsolete

tazzman

Recruit
Joined
Aug 19, 2009
Messages
2
I have a 1972 50 HP Johnson outboard which will not engage the prop when selected forward or reverse. The engine speeds up but prop does not turn. It is a hydro electric shift. I have traced the problem back to the switch in the remote control box. This switch is obsolete so does anybody know where I can find a switch.
 
Last edited:

R.Johnson

Rear Admiral
Joined
Sep 24, 2003
Messages
4,446
Re: Gear Shift Problems

Re: Gear Shift Problems

That unit is a hydro-electric shift. It must be running, or cranking over to shift. It should always default to forward gear when at rest.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Gear Shift Problems

Re: Gear Shift Problems

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.
 

tazzman

Recruit
Joined
Aug 19, 2009
Messages
2
Re: Gear Shift Problems

Re: Gear Shift Problems

Thanks for the info!

I completed the tests that were recommended above and have now traced the problem back to a defective switch in the remote control box but unfortunately the part is obsolete. Has anybody else had this problem and if so how did you fix it? I've tried to find a used control unit but no luck.
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Gear Shift Problems

Re: Gear Shift Problems

You are have to find a salvage yard. Sometimes e-bay will have complete control boxes for auction.
 

oldrudedude

Chief Petty Officer
Joined
Jul 3, 2008
Messages
480
Re: 1972 50 hp Johnson Part Obsolete

Try taking the selector switch apart and cleaning it. Claen the inner contacts then test for continuity.
 

bonz_d

Vice Admiral
Joined
Apr 22, 2008
Messages
5,276
Re: 1972 50 hp Johnson Part Obsolete

There is an old marina located in Fox Lake Il. that when I was there this past spring he had a number of those old control boxes piled in a corner. If interested met me know and I'll get you a contact.
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1972 50 hp Johnson Part Obsolete

F_R found a source and part # for the shift switch, the other day, but cannot find post. you might send him a PM.
 
Top