Road Construction Johnson

[Mumbles]

Yup, they have the pressure/vacuum cooling system instead of a water pump. It has to be in motion on a boat to keep cool but there is a way around that. On the bottom of the block there should be a pipe plug which can be removed so a garden hose can be hooked up for running on a stand. They also like an 8:1 fuel mix.

[bullie]

Thanks Mumbles! I appreciate the info. Strange with the 8:1, it doesn’t smoke as much as I would have expected.

Kinda cool to get this one going.

[bullie]

Ok. Back to this one. I took it out for a spin and it lost spark on one cylinder. I pulled the flywheel and cleaned the points again but still have no spark on that cylinder.

So for my green guy questions. How do I check a coil that doesn’t have connections I can loosen? And, I was thinking it may be the condenser going bad. They are under the mag plate? Availability?

[RICHARD A. WHITE]

Those need to be on a moving boat to cool properly….

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[garry-in-michigan]

Early models had a single coil and two flats for the breaker points. The flywheel acted as a distributor, shorting out the un used spark plug wire. I am not sure when they switched to the two coil system. If it has a single coil, look for a short in the distributer system. Cleaning usually fixes it. . . 🙂

[bullie]

This one has two coils.

[Mumbles]

quote Bullie:

How do I check a coil that doesn’t have connections I can loosen?

You can’t. Well you can but it’s better to break out the tools and undo the coils primary lead at the points. The other way would involve isolating the condenser from ground and preventing the points from making contact before hooking up your meter.

If my memory serves me right, I think the square caps in my KA-37 were good and didn’t need replacing. If I did swap them out, I would have used these .22 uF Vishay caps from Digi-Key which I have used successfully in many motors.

https://www.digikey.com/products/en?ven … =bc2609-nd

I think this mag was out of a KA-38 so it should be the same as yours.

---

Attachments:

[bullie]

Yep. Looks like that one.

[Anonymous]

This motor has no water pump, running in a barrel will over heat the motor. It uses forward motion of the boat and the prop wash to force water into the water scoop to fill the water system and gravity to make the water to flow though the cooling system. When running on a boat, start the motor and run to full speed on plane to purge air and start the cooling water flow. after doing this you may slow down and idle along, but do not make a hard turn at idle as you will interrupt the cooling flow and start over heating. It’s called a pressure vacuum system.

[mike-stroz]

I really like that series of motors. I run a KA-38 on my 14′ rowboat all summer long. Nice and smooth, quiet, and pretty powerful

[Author]

Posts