Identify this lower unit?

[davidk]

Can anyone identify this lower unit (what motor it fits) by the photos here?
Thanks, -DK

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[Randy in Tampa]

model 6039 Speeditwin lower unit, there were three different lower units as I remember that would be the newest, I think 😎

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[davidk]

Awesome! Thanks for your help, Randy!
-Dave

[garry-in-michigan]

Those were used on Speeditwins and Speedifours around 1947-1948. Origenly designed for the 50 horse "Storm boat motor" they had wings on the gear case to help protect the propeller. They had a couple thousand in stock preparing a big shipment for the invasion of Japan. They were suddenly surplus when President Truman dropped the A Bombs on Japan, so they used them where they could. They ran out in ’47 and the next castings were without the wings. (Most people were sawing them off anyway) In 1949 they redesigned the lower unit and added a rear water pickup in 1950. The full shift Big Twin came out in 1951. . . 😀

[davidk]

Very interesting, Gary. Thanks for the details!
-DK

[Tom]

David, it’s tough to tell without a ruler in the photo for size, but it looks to be smaller than the Speeditwin lower unit. And the number seems early. Without seeing it in person, I think it looks like something from an early Sportfour or Elto Super A.

Tom

Edit: OK, a little more research indicates that the bolt pattern isn’t right for the Sportfour or the Super A. Those had the bolts outside the exhaust inlet. What size prop will fit?

Tom

[twostroke]

I agree….it looks exactly like the one on my (God-awful heavy!) Sportfour. I can supply dimensions tonight if you you tell me what you wanna’ know.

Jim

I say "pardon me" a lot. I had a 20H, then raced open mod sleds.

[davidk]

There are so many great reasons to belong to this club! So much knowledge and eagerness to help.

[garry-in-michigan]

The Sportfour lower unit is quiet different . . . 😕

[Anonymous]

Late 1947,1948,1949 Speeditwin and Speedifour

[Author]

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