For those interested in such things, the motor that came with the Batboat I bought turns out to be a very desirable one. A 35 horsepower Evinrude Lark Super Quiet, model 35514. It was made in 1958.
Desirable, I've learned, because of the straight forward mechanics. Like a Jeep, there are only a few things that can go wrong with them and they are not complicated fixes.
There are so many of them in use some parts are still made.
One of the fins, or anti-cavitation plates, is broke. But I am told these sections can be found cheap and plentiful. Its job is to help prevent the propeller from sucking in air from the surface of the water. However, if the prop is low enough in the water it won't need that part.
This is one of the reasons why I feel I got a good deal on the boat.