Elto built 4000 Handitwins in 1940. Models with serial numbers of 4001 and higher were built in 1941. 1942 production was stopped by the start of World War Two. It is a two cylinder apposed motor with a bore of 1-¾" and a stroke of 1-⅜" for a piston displacement or 6.07 cubic inches. It’s 3 horse power is rated at 3,500 RPM. The fuel tank holds 3-½ pints and will run the engine upwards to an hour depending on load. It is water cooled by an aluminum veined two stage centripetal pump at the top of the gearcase. It weighs 31 & ½ pounds and sold for $68.50 FOB Milwaukee Wisconsin in 1940.

The powerhead is floated on the 4 rubber balls (200048) to absorb vibration. (Dad bought a bunch as non-lethal sling shot ammunition to ward off unwanted animals in our yard. They were very effective.) They nest in 4 sockets in the steering handle support bracket. The steering friction is adjusted by the 132124 pivot bearing clamp screws. It should be just tight enough to keep the outboard on course. The recommended Champion C-7 spark plugs have been replaced by Champion 516 gapped at .025". The breaker points are set at .020"

The carburetor check valve lift should be 9/64" – valve spring pressure should be 3 ounces – Fuel level in the float bowl should be 13/16" down from the rim when held level. . . . 😀

It most likely had a shim in one place or the other, or both when new,
but I guess I’d check the backlash and go from there.

In looking at the parts diagram, it looks like if you made the
thrust plug longer, that it would push the prop shaft, and
hence driven gear, further away from the drive gear, and
ending up in “more” backlash. Then again, without
the actual parts in front of me, I’m just guessing.

My little bit of automotive training almost 50 years ago,
taught us to use bluing grease on the pinion and differential
gears, rotating them, to check the actual gear mesh, making
sure the gears were meshing near full depth and in the
centers of the teeth.

On the lower horse power motors, I pretty much go by “feel”
when checking the backlash, but none of my motors
see much use.

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T....in Wisconsin