1957 Johnson serial numbers were from 1493186 to 1660474, so that freeze plug says its a 1957. I’m thinking it may be a ’57 35 HP Golden Javelin, which, if I remember right, had a white powerhead.
That being said, don’t rule out that someone who is good at it, may have swapped the freeze plug, but I doubt it. If it has a thermostat, it could be 1959 or newer, or a 1958 Super Sea Horse 35.
The powerhead could have been re-painted white also, but if that’s the case, you should see signs of paint flaking with another color underneath.
Dave
