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Sears Waterwitch Mixer Design

JF671

Subscriber
Last Subscription Date
12/11/2019
Over the weekend I came across this neat bit of engineering while resurrecting an old Sears Waterwitch outboard boat motor. The engine is of air cooled two stroke design, with a jug that looks like that of a washing machine engine. These engines were only built for a few years, first rated at 3/4HP and later upped to 1HP. In place of the more conventional reed valves or piston porting, this engine has poppet valve placed in the intake opening, to hold the pressure created during the power stroke. Within the seat of the poppet valve is the fuel metering jet, which allows the engine to draw fuel only as the engine draws air. This is pretty handy as other than that, the gravity fuel system has only a mixture needle to control the rate of which the fuel leaves the tank. It’s stupid simple, kind of like setting a faucet to a slow drip. There are no throttle plates, fuel shut off valves, floats or check valves within the fuel system. Closing the mixture screw, a good seal on the poppet valve and seat and a closeable tank vent are really all that prevents the loss of fuel while at rest. Variable engine speed is gained only be adjusting the ignition timing and fuel mixture.

Here a short first run video (please excuse the really cluttered test bench):

 

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Preston Wells

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Age
59
Last Subscription Date
02/05/2020
The poppet valve is a lost technology that as you described worked well and was pretty efficient. Johnson, Evinrude, Gale and Muncie to name a few also used the poppet valve intake system. Nice review.
 

JF671

Subscriber
Last Subscription Date
12/11/2019
What I've found online shows a fairly short production run of 1939-1942.
 

JoeCB

Subscriber
Last Subscription Date
03/19/2020
JF, thanks for posting the video, always good to hear a old outboard coming to life. Your Sears Waterwitch was made by the Kissel Industery Co,Hartford WI. 1938 - 1940, It should have a model number stamped somewhere 571-30 (1938) 0r 571-31 (1939).
That little motor went to 1 HP in 1941 with the change to a float style carburetor. You can find a lot more info on your motor and all old outboards at the Antique Outboard Motor Club site aomci.org … check it out :)

Joe B
 

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