72 Johnson won't go into gear

[ziggy101]

I rebuild the engine on my 50Hp Johnson last summer/fall and put it in the water ran it for quite awhile and then tried to take it for a test drive and it would not go into gear. i had changed the oil in the lower unit earlier in the summer, and only ran it in water once. i checked it after i pulled it from the water and it had about 1/2 cup of water in the oil. this is a hydro electric

do i need to rebuild the lower unit? if so how big a job is that and can i get parts?

 

[HighTrim]

Re: 72 Johnson won't go into gear

When you changed the gear oil, did you change the gaskets on the drain and vent screw? That is the number 1 spot for water intrusion. I would change those, re fill, then monitor the oil. The water is heavier than the oil, and will sit at the bottom of the gearcase, allowing you to see it immediately after the drain screw is removed. If water is still present, you will either need to pressure test the lu, or simply re seal it all.

 

[HighTrim]

Re: 72 Johnson won't go into gear

To pressure/vacuum test a lower unit:

a) drain the gear oil
b) use an appropriate adapter with a gauge tee'd in to apply pressure or vacuum. No more than 15 psig for pressure. You can use a bicycle pump or any other compressed air source for pressure. For vacuum, you need a vacuum pump.
c) LU should retain some pressure or vacuum for 45 minutes minimum.
d) If pressure doesn't hold, submerge LU in water to find leak source [possibilities: drive shaft seal, prop shaft seal(s) (usually two), shift shaft seal and the fill/drain screw washers.]
e) replace offending seal(s) as required.

 

[ziggy101]

Re: 72 Johnson won't go into gear

thanks for the information, i do not think there are any gaskets on these screws, so that might be the problem - boy that would be nice. I might just go ahead and try the pressure test as well to know i have it.

 

[tashasdaddy]

Re: 72 Johnson won't go into gear

did you use the special Premium Blend Type C lower unit oil. it is the only oil for hydro-electric shift motors. if you use standard low unit oil, this could be the problem.

 

[Faztbullet]

Re: 72 Johnson won't go into gear

If it is a elecric shift which a 1972 should be, It should be in gear when you first start it then neutral. Pump has to build pressure to push clutch dog to neutral. If it is doing this you may have a switch or pushbutton bad. If rusted up internally I would say it would be stuck in foward. Make sure you use a oil designed for electric shift as it is non-conductive.

 

[F_R]

Re: 72 Johnson won't go into gear

Which gear will it not go into? It is supposed to be in forward gear all the time, till you tell it to go into neutral or reverse by using the control. In other words it should be in forward gear, just sitting on the trailer and not running. Furthermore, it won't shift at all unless it is running.

OK, with that in mind, if it isn't in forward while not running, the piston is stuck in the oil pump and there is no way to do anything with it other than a complete lower unit tear down. Sorry 'bout that.

EDIT: If it is the piston stuck (in neutral), you MAY be able to kick it loose by shifting to reverse (engine running). But that is a big maybe and it will be apt to stick again till the real problem is fixed.

 

[ziggy101]

Re: 72 Johnson won't go into gear

when it is shut off, it is in gear, if i turn the prop in this case it will start to turn the engine over. But when when the engine is on, it will not go into forward or reverse.