Re: 1962 40 hp evinrude choke dilemma
Ive begun to restore this motor model # 35531M. It has a choke system I have not seen before on these motors. coming off the side of the carb is a housing that is controlled by a vaccume switch, the choke when cold is closed, upon starting the vaccume ****ch pulls it open and Im guessing remains that way till engine is cut. inside of the housing is a heat coil and has a hose connected from the crankcase pushing the gas/ oil mixture through and returning to the crankcase, Im guessing after the engine heats up the fuel is warmed too and when it hits the coil it expandes , keeping the choke open after the engine is cut so you can restart the warm engine. My question is this: Is this all worth the trouble. I plan on putting on a tiller arm and could just as easily pull the choke open and closed by hand. Has anyone used this system? Is it reliable? or is it junk. My thought is that I have not seen this on any other motors, maybe there is a reason for that. Thanks Ronnie
Well OK, here is the deal: That is a water heated automatic choke. It also has a vacuum diaphrgam to partially open it when the engine starts to prevent overchoking and flooding out.
The hookups are a hose running from the cylinder water jacket to the top of the choke housing. Another hose runs from the bottom of the choke housing to the exhaust housing, where it attaches to a fitting that goes into the return water line. A third hose connects the vacuum diaphragm chamber to the intake manifold.
When you start a cold engine, the choke is closed. As soon at it starts, the vacuum pulls the choke part way open, but it is held part way closed by the bi-metal spring inside the red choke housing. As the motor warms up, water flowing from the water jacket, through the choke housing, to the water return tube, warms the choke housing and the bi-metal spring inside. As the bi-metal spring warms, it expands, allowing the choke to fully open.
That's the way they are supposed to work anyhow. Truth is, most of them didn't work worth a hoot even when brand new. Most owners got used to just opening the door to operate the manual choke. There is no need to remove or relocate any hoses because the manual choke overrides the automatic feature. If you insist though, you can remove the hoses and plug the fittings. Or remove the fittings too, and plug the pipe threads in the respective ports.
EDIT: BTW, even if the automatic choke is perfect, it won't work unless the cooling system thermostat is working. The thermostat is what makes the motor warm up, which is what makes the water flowing to the choke warm up, which is what warms the housing and bi-metal spring.
