Johnson SD 20 Gearcase Lubrication Question

[sedover]

Looking for a SD20 gearcase expert so that I can understand how the upper seal and bushing are lubricated. I have a SD20 that has been recommissioned after a 40 yr nap since I last ran it. Engine was stored properly and has just been run and runs great.

Just want to make sure I am not missing something. Does the lubricant essentially splash up to the bushing from the lower gear housing through the pinion gear bearing and via the driveshaft cavity. It’s the location of the vent screw/plug which leads me to be concerned. That gear lube level is a long way from that bushing

Thanks

Steve in SE Michigan

[david-bartlett]

Steve,

That is the way I see it working on mine. I did "overfill" just a bit, but nowhere near the top of the cavity. No problems thus far!

There is quite a learning curve with these motors, compared to the newer ones with the synched carb/ignition. Need 3 arms to run one.

[sedover]

Can relate to the 3 arms.

Found it to be an excellent runner. With the separate spark and carb controls you can really dial it in at whatever speed chosen.

I have a dis-assembled parts motor that I carefully examined to make sure I wasn’t shooting myself in the foot on the gearcase issue. Will do a post season teardown for my own info.

Evaluated the cooling system with an infrared temp reader during sea trial, yes, the hood was off. Seemed to be operating correctly with the expected hot spots. Forgot to bring a tach, next time. Only threw it on top for an easy cruise speed, no WOT, just purred along.

[Author]

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