72 johnson no neutral no reverse

adam22

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May 3, 2003
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22
I recently purchased a 1972 Johnson 50 horsepower<br />motor. The engine runs great, but it will not go into reverse or neutral. It makes no grinding sounds or anything like that. Even when I place the shifter in reverse it is still in forward. I know that it is shifted electrically, but I do not know how it works or how it should be wired. Any help would be greatly appreciated.
 

boatbob

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Feb 10, 2003
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Re: 72 johnson no neutral no reverse

sounds like you have either bad shift solenoids ot wiring problems others in the forum can give more detailed info
 

adam22

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May 3, 2003
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Re: 72 johnson no neutral no reverse

I don't know how to the solenoids should be wired up. I found the blue and green wires were disconnected from the solenoids. I reconnected them but still no reverse or neutral. The wiring has been tampered with. I am looking for a wiring schematic, but I cannot find one.
 

JB

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Mar 25, 2001
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45,907
Re: 72 johnson no neutral no reverse

Ahoy, Adam.<br /><br />Your engine is shifted by hydraulic pressure controlled by electric solenoid operated valves.<br /><br />If the hydraulic pump in the lower end fails or it has incorrect fluid it will not shift. Special fluid is required for this gearbox. <br /><br />If the hydraulic system is working correctly but there is no power to the solenoids it will not shift.<br /><br />If either the hydraulic or electrical systems fail it will stay in Forward.<br /><br />So. Do you get a click in the gearbox when you shift? If so, drain and flush the lower end and refill with OMC Hydro-Electric lower end fluid.<br /><br />If there is no click you have an electrical failure. You will need to get or borrow (library?) a manual to trace an electrical problem.<br /><br />It is not likely that both shifting solenoids in the lower end would be bad, though it is possible.<br /><br />Let us know what you find. :)
 

Joe Reeves

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Feb 24, 2002
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13,262
Re: 72 johnson no neutral no reverse

Adam.... The following may be of interest to you.<br /><br />(Hydro Electric Shift)<br /><br />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.<br /> <br />You CAN NOT use HI VIS lube in that lower unit. You MUST USE what OMC calls "Preminum Blend" lube, commonly called "Type C". (A thinner lube) <br /><br />In neutral, you need 12v to the "Green" wire. <br />In reverse, you need 12v to both wires, the "Green" one and the "Blue" one. <br />In forward, there should be no voltage to either wire. (The spring loaded shifter dog forces the unit into forward gear) <br /><br />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. <br /><br />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).<br /> <br />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.
 
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