lower unit drive shaft seal for ’68 100 hp V4 Johnson?

[boatman]

Hi all,

Drained the lube in the lower unit of my ’68 100 hp V4 Johnson. The Type C fluid was milky, so water is getting in somewhere. One of my local AOMCI chapter friends said the drive shaft seal below the water pump is the most likely culprit. I’m more familiar with the 40 hp and under OMC motors and haven’t worked on these V4 electric shift lowers before. Are any special tools required to pull this seal? I assume the drive shaft comes out and I can use a seal puller or screw driver to remove the seal. Any idea if I can find this seal at a local distributor like Motion Industries or is there another good source? Marine engine.com?

Thanks to Frank and Fleetwin for their advice on getting the stuck shift wires to release from the midsection so I could drop the lower unit and replace the impeller. Sprayed the rubber coated wires down with silicone some months back and they pulled free with little effort today. Just in time, as one vane had already broken off the old impeller.

Thanks,
Paul

[dan-in-tn]

Well unfortunately the driveshaft doesn’t just slide up & out. It has a pinion nut that holds the pinion gear on a taper. It is kind of hard to assume any particular seal is your problem. It would be better to replace the seals on a motor of this age! The seals under the water pump plate are back to back. #312083 & available from ME. The propshaft seals are back to back also. #310599 or 18-2012 Sierra also from ME. The propshaft seals can be gotten to by pulling the end cap. This way you don’t disturb everything else & don’t have to have special tools. If I am forgetting anything someone will be along to set me straight. Been a long time since I have done one of these dinosaurs. Best of luck to you!

Dan in TN
PS: Be sure & get an O-ring for the rear cap #310414. Almost forgot that!

[boatman]

Dan,
Thank you.
Paul

[frankr]

It’s been many moons since I’ve worked on one too. But I think the seals under the pump are pressed into a removable plate. No need to remove the driveshaft.

[fleetwin]

Well, if the gearcase is still assembled, I would recommend pressure testing first to make sure you find the actual problem….Replacing all the seals/orings may not solve the problem if there is a defect in one of the housings or shafts….
And one thing is for sure, you do not want water in this gearcase! Very expensive to repair.

[Author]

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