That looks like an early 1970s motor originally made by a company in New York – I think something like Seaway or Seaborne. They started out using Ohlson & Rice powerheads. O&R made model airplane motors, chain saw motors, bicycle motors and other small motor applications. There are also some current model Aquabugs made by a company called Bike Bug that uses a Tanaka powerhead – those things look like a modified weedeater. No idea of value on one of these original models like yours.