1968 Johnson 40 HP RDSL-30-C exhaust cov.

[Taney37]

Cleaning up a 1968 40 HP Johnson RDSL-30-C motor. The top of the exhaust cover has a fitting with tubing running to the automatic choke. There is a similar fitting on the exhaust cover below this tubing. It is threaded but nothing is attached to it. What is the purpose of this lower cover fitting?

 

[racerone]

Very common question.----And a very good question too.-------Facts------That is the air inlet to a heat exchanger.----The heat exhanger is inside the exhaust manifold.----The air is pulled towards and into the carburetor via that long tube.------The hot air goes over a bi-metallic spring to control tension on the automatic choke flapper.----That is it and simple I think.

 

[Taney37]

Thanks for the info. Always makes me nervous to see an open fitting and not know why it's there!