72 model hydro electric shift

[pjpoppet]

Hi all, new member here from Sydney Australia, was hoping someone may be able to help with potential problem on a lower unit on Johnson 70 hp electric shift, has reverse, neutral, however no forward, took it out this afternoon, whilst powering up a couple of times it felt as though we ran over something, (thudding), we continued along slowly until had no forward gear anymore, we reversed all the way back to ramp, my limited knowledge tells me that the solenoids are all ok, hence having reverse and neutral, forward is the default position, could it be the clutch dog and if so, how hard is it to remove the electric type lower unit, I am a car mechanic by trade, so tools are not a problem and neither is mechanical ability, any help with this greatly appreciated, cheers Justin.,

 

[rodbolt]

Re: 72 model hydro electric shift

wow
very odd as that lower is designed to shift into fwd in the event of any electrical or hydrualic failure.
remove the prop and check the hub.
the shift clutch is spring loaded to force the clutch into the fwd position any time both solinoids are deenergized or there is a loss of hydraulic pressure.
look for the green and blue shift wires where they exit the adapter and enter the powerhead area.
dissconect the knife connectors
with key on and engine off test the voltage on each wire from the wire to ground with the shifter in fwd.
should have NO voltage.
if voltage is presant check the shift switch and wiring.
ALWAYS be very careful and very aware that any failure while the engine is running will result in prop shaft turning.
keep away from the prop or remove it while testing.
but carefully test the prop hub first.

 

[F_R]

Re: 72 model hydro electric shift

wow
very odd as that lower is designed to shift into fwd in the event of any electrical or hydrualic failure.
remove the prop and check the hub.
the shift clutch is spring loaded to force the clutch into the fwd position any time both solinoids are deenergized or there is a loss of hydraulic pressure.
look for the green and blue shift wires where they exit the adapter and enter the powerhead area.
dissconect the knife connectors
with key on and engine off test the voltage on each wire from the wire to ground with the shifter in fwd.
should have NO voltage.
if voltage is presant check the shift switch and wiring.
ALWAYS be very careful and very aware that any failure while the engine is running will result in prop shaft turning. keep away from the prop or remove it while testing.
but carefully test the prop hub first.

The quick and easy way is just run it with the wires disconnected. If it is in forward gear and doesn't jump out or grind, it isn't the clutch dog.

However, if it doesn't have forward with the wires disconnected, there has to be some mechanical problem within the gearcase, either holding the neutral valve closed, or keeping the clutch dog from sliding forward and engaging the forward gear. The piston that moves the clutch dog is a very close fit in the oil pump. Perhaps there are dirt, grit, or chips imbedded in there and keep it from sliding freely.