Johnson 300 1935-36

[geary]

Guys,
We’ve been working on this engine for a couple weeks now and still can’t get it to run consistently ! So far here’s what we’ve done. Compression is 65 lbs both cylinders, cleaned points checked coils and condensers, it has good spark ! We could get it to fire a couple times just trying it on a stand, but not in a test drum of water. Re-magnetized the flywheel magnets and got a nice blue spark that jumped a 3/16 gap !

Tried it again in the test drum with water, it started but we couldn’t fine tune it by adjusting the needles, it would die as soon as we tried adjusting either the hi or low speed adjustments.

Pulled the carburetor again and went thru it completely cleaning all passages and ports ! Didn’t find anything that seemed to indicate a problem ! Tightened the hi-spd packing nut and cleaned the low-spd needle felt washer and spring !

At this point we are ready to try it again ! But is there a possibility the rotary valve in the crankcase could be worn enough that it is not allowing the carburetor adjustments to correct the hard starting and running ? Any suggestions and help would be appreciated !

Gary & Paul

[Tubs]

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

• This reply was modified 4 years, 6 months ago by Tubs.

[lloyd]

I agree it is probably low compression. I would expect that motor to have at least 75 psi cold and dry.

[Tubs]

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

• This reply was modified 4 years, 6 months ago by Tubs.

[Mumbles]

You might want to try soaking the pistons and cylinders for a while with Sea Foam to help break up or dissolve any sludge or carbon buildup which may be causing the rings to stick. These motors used automotive oil mixed with the gas back in the day and it was terrible for leaving carbon deposits everywhere.

Running on a stand but not in water can also be caused by poor sealing in the crankcase. Using a heavier oil, such as a 40W aviation oil, can help to seal any worn crank bearings.

https://youtu.be/-wWAGHnOwGg

[Tubs]

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

• This reply was modified 4 years, 6 months ago by Tubs.

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