Your motor is a model 492 seaking it was made in 1935 -36 it was 8.5 hp and made by Evinrude which was called OMC at that time, It was basically the same thing as the Fleetwin with a few minor differences , you can verify this in the old outboard book on page 235 and it does have a metal impeller and your carburetor and gearcase are interchangeable with the early fleetwins and sportfours, I hope this helps 🙂