Johnson 300 Lower Unit removal

[Tom]

I have a pretty crusty Johnson 300, but the powerhead seems good. The driveshaft and propshaft are both very tight in the lower unit. I’ve removed the rear carrier with the prop shaft and water pump, but I can’t seem to get the lower unit off of the down tube. This motor has a two piece driveshaft.

I’ve removed the through bolt at the top of the lower unit, and the gland nut fitting above it. Heating, penetrant, verbal encouragement, and hammering on a block of wood have all left the lower unit it its original state.

So is there something I’m missing? or should I just be patient with heating and penetrant?

Thanks for any tips.

Tom

[Mumbles]

What about the BIG nut on the bottom of the down tube? There’s a plain nut on the front and the water tube fitting at the rear acts as a nut to. The pinch bolt is out so it should come apart as there is only a tab at the top of the driveshaft connecting it to the crankshaft. No rusty splines to deal with on these ones!

Right above the pinion gear is the 39-65 collar which has to be pried up so you can drive the 18-84 pin out. Once it is out, the pinion shaft should come out of the housing leaving the pinion behind.

I can’t find any good photos of one disassembled but I can always go over and take a look at a couple of gearcases I have in storage.

---

Attachments:

Johnson 300 Parts.PDF

[Tom]

Mumbles,

Thanks for the information. I’ve got all of the things you mentioned covered, so I’ll just go at it slowly.

Very interesting motor!

Tom

[Mumbles]

I’m not sure if you saw it but the parts PDF is at the top of the first photo.

[Tom]

Thanks, I’ve got that!

T

[jim-moffatt]

Its really a fun motor to run.
Some tips from memory: because the rotary valve is above the carb and its basically an updraft, its almost impossible to flood. It needs lots of choke to start cold and in my experience even some to start hot.
it was conceived as a "high speed" motor and runs best with the correct low-pitch prop designed for it. It will run with a J70 prop but not as well, An F70 prop has way too much pitch.
Happy putting!

[Mumbles]

quote Tom Manley:

Very interesting motor!

They are a unique motor, being designed and built during the art deco and great depression years. They were Johnsons first attempt at shrouding a motor, with the one piece carb on the front flowing into the smooth cylinders. Evinrude may have had the first reed valves in ’35 but Johnson had the first covered powerhead!

Here’s a short video of one I had shipped out from Ontario (Thanks Westwind) puttin away. It wouldn’t run right at first but after charging the magnets, it came back to life.

https://www.youtube.com/watch?v=-wWAGHnOwGg

[fisherman6]

I have one of these that I need to work on one of these days. This thread is giving me a bit more inspiration to get mine going again.
– Ben

OldJohnnyRude on YouTube

[Tom]

This is actually my second one. I have a nice original that I’ve run, and I like it a lot. Quite a mix of technologies. I never managed to get the lower unit loose on this one, but got enough penetrant into the lower pinion shaft bearing to loosen it up. I’ll go through the rest of it, and see how it runs.

T

[need2fish]

https://www.youtube.com/watch?v=QQqJ9bUJwU4

by KevinRude

[Author]

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