1971 125 HP Evinrude Lower Unit Shift Problem

[jckulluk]

The motor won't shift into forward or reverse it just sticks in neutral with the engine running, but when I turn it off it goes back to forward. I know it's not an electrical problem, I done all of the troubleshooting from the manual and I've check all the diodes, I've check the Solenoids which Ohm out to 5 Ohms, I've checked my control unit. I've also read about an oil pump in the shift assembly, does anyone know anything about this? When I opened the lower unit my oil was milky.

I've read that the lower unit won't shift when there's water in it mixed with the oil, so I'm thinking I need to buy all new seals and possibly a new shifter cover assembly. Do I need to put in the new shifter cover assembly if there might be a water leak in it or can I use the existing part and just replace the seals.

Any help or advice would be appreciated.

 

[F_R]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

So, you are positive it isn't an electrical problem, right? I still gotta ask, does it go into neutral with the wires unhooked by the powerhead? It should not. It should stay in forward with the wires disconnected.

OK, you have an unusual situation if it is defaulting to neutral when running and no electrical connection. I would suspect the solenoids are incorrectly adjusted or incorrectly installed, holding the control valves closed.

But here is how it works. You can see a picture at http://shop2.evinrude.com/ext/index.aspx?s1=fc502fad3f51ed0e319aa8bdd7efb79a The oil pump is in the nose of the gearcase. A piston slides in and out of the oil pump to move the clutch dog. Those parts are obviously working or it wouldn't be going to neutral.

The oil pump pumps oil, applied to the piston. A pair of control valves are between the oil pump output and head of the piston. The solenoids close the control valves when energized. When neither valve is closed, oil merely flows out through the valves instead of applying pressure to the piston. Energizing one solenoid (green wire) closes the first control valve. That causes oil pressure to be applied to the head of the piston and move it to the neutral position. Once it gets to the neutral position, the oil is bypassed through the other control valve (which is still open) so it doesn't go all the way to reverse. Energizing the blue wire solenoid (first one still energized) closes the second control valve. Now they are both closed and the oil cannot escape from the head of the piston till it is pushed all the way back to engage the reverse gear.

De-energizing both solenoids opens both valves, pressure is relieved from the piston, and a spring pushes it forward to forward gear.

Clear as mud soup?

 

[bigpoppakdog]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

Hey frank, could this be a problem in the control box? When my box started going out, it would want to stay in neutral all the time unless I pushed hard and held down the forward button.

 

[Joe Reeves]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

Hydro Electric Shift System Explained)
(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)

Note: The engine must be running OR have the driveshaft turning by some other means in order for the engine to shift.

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.

 

[jckulluk]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

So the fact that there was water in the oil would not keep it in neutral?

 

[jckulluk]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

I just went and double checked it no voltage to the solenoids when its run so it must be the incorrectly installed solenoid rod are those things hollow maybe one is plugged ?

 

[jckulluk]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

Ok i went back and looked at the soleniods they where in correctly adjusted Manuel says to have the ends flush with top of soleniod is this correct ?

 

[F_R]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

That is correct. And no, they are not an oil passage. The rods hold levers down that holds the valve ball on it's seat. Water in the oil won't make it go into neutral, but it might make it stick in neutral. It is the debris that it causes that makes it stick.

 

[jckulluk]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

So I actually had to adjust both of the rods to make them flush with the top of the solenoid so hopefully that was my problem.Also I had a question if this doesnt work could I just take both of them out and run it in forward all the time?

 

[F_R]

Re: 1971 125 HP Evinrude Lower Unit Shift Problem

Well, I've never heard of that cure, but I suppose you can. Durned if I'd put up with something like that though.