Bypass purpose

[Ky Howard]

Can anyone tell me the purpose of the bypass on my '72 Evinrude 18 hp (1820 2R) E04350. There is a tiny fitting (1/16th tubing) that exits the bypass cover and leads to a 1/4 fitting in the crankcase. Is that for a model with an electric primer for cold starts? Mine is tiller with no auto primer, so I'm guessing it just vents back to the crankcase. Can anyone confirm that?

 

[racerone]

They never had electric primers in 1972 model years.----The electric primer was initiated in 1980 I think.

 

[fdrgator]

Crankcase drain hose. It drains off the fuel that puddles up in the crankcase and injects it into the upper cylinder for burning. A terrible solution, but it kept the EPA happy. Sure pe-e-e-e-d off a lot of customers that previously owned older models though. But consider how lousy the smog-control cars ran at that time also.

 

[Ky Howard]

Hmmmmm, so if it was plugged on the crankcase side...and the cylinder side was used for a manual primer...it would provide direct access to the cylinders for quick starting..

 

[Ky Howard]

of course, that's only a theory....

 

[fdrgator]

I've always been happy with the good old flapper choke. To each his own, I reckon.