1968 40 Hp Johnson big twin drops out of gear

[matthewrg]

Hi I?m new to the site I have a 1968 Johnson 40Hp electro shift, my problem is intermittent loss of gears, sometimes I can get 2 hours of work out of it with no issue, sometimes I loose forwards or reverse or sometimes both, sometimes it comes good and sometimes I have to get a tow. Both coils test out at 7.8 Ohms which I think is normal, the oil in the gearbox is cloudy (i.e. has water in it) I am using the type c oil, I plan on replacing the seals in the leg, but should I pull the gearbox apart could the dog clutch be the problem? The water/oil mix doesn't seem to change the resistance? Any ideas would be greatly appreciated.
Regards,
Matt

 

[tashasdaddy]

Re: 1968 40 Hp Johnson big twin drops out of gear

clutch dog #1, shorting wiring to shift.

 

[tx1961whaler]

Re: 1968 40 Hp Johnson big twin drops out of gear

clutch dog #1, shorting wiring to shift.

TD, is there really a clutch dog in the 40 electromatic, or is it the solenoid/capture spring arrangement?

Change the oil and check the wiring and switch first. If it will run for hours without slipping, then it is probably not a mechanical issue.

 

[F_R]

Re: 1968 40 Hp Johnson big twin drops out of gear

TD, is there really a clutch dog in the 40 electromatic, or is it the solenoid/capture spring arrangement?

Change the oil and check the wiring and switch first. If it will run for hours without slipping, then it is probably not a mechanical issue.

Agreed, there is no clutch dog in an Electramatic. Also agree, always change the oil first and check the electrical next--especially the shift switch in the control. Do a voltage check at the blue and green wires where they go down to the lower unit (motor not running). Should be battery voltage every time you shift into gear (don't disconnect the wires to do this check). Shift back and forth a bunch of times to look for an intermittant problem.

 

[tashasdaddy]

Re: 1968 40 Hp Johnson big twin drops out of gear

ok, i'm wrong, learn something.

 

[hawkman222]

Re: 1968 40 Hp Johnson big twin drops out of gear

I had to tear into my 1970 40HP last year. What you have in that gearbox are a forward and reverse gear both with a hub on each end. Around the hub is a 'spring', for lack of the proper teminology, that contracts and squeezes down on the hub when the coil is energized. This causes the the gear to drive the shaft. The forward gear has a knurled hub the reverse doesn't. Kind of hard to explain without looking at it. On mine the spring was about half gone on the forward gear. I beleive the 2 coils are completely independent. If occasioally you're loosing both forward and reverse, I'd look at the switch at the control box and wiring. If you do feel the need to open up the gearbox, be very careful. The wires going to the coils are very delicate and are easily broken. Big $$$$$ to replace. You have to seperate the gearbox at the first flange above the gearbox and carefully disconnect the knife connectors before removing the gearbox, and they don't give you much room to work before the wires get tight. Maybe more info than you need, just thought I'd share my experience.

 

[matthewrg]

Re: 1968 40 Hp Johnson big twin drops out of gear

Thank you all for you ideas I have replaced the shift switch at the throtle control have pulled the leg down from power head to top of gearbox and replaced the cable with a high temp silicone this did'nt seem to make a difference. I'm really cautious with pulling the lower gearcase apart looks like too many things to go wrong. I have now removed all wires and tape covering them between the gunnel and motor. I have found that the wire that comes back from the starter motor to the ignition switch and then powers the gear selection was broken apart and had corosion and burn marks on the ends and plan to replace all of them with flexible welding wire. I have been to the boat shop and bought a seal kit for the leg gaskets and will replace the seals on the oil input screws aswell. Do you know what sort of seal to use on the screws? Is there a way to reverse pressure test the gear box maybe with an air compressor, (the oil is milky could this be the problem? I have changed it and the new stuff also became milky quickly) If i run the motor in gear, in a large tub of water will this be enough to see if water can get in?
kind regards to all,
Thankyou,
Matthew