I dont know riverrat, those old evinrudes dont have much thrust… not sure it actually would get you up river. Most guys use 6hp outboards for “kickers”, and these are high thrust motors, I know for a fact a 6hp kicker (about 5X as much thrust as yours) will not push a 16’ tracker upriver here.. I watched a guy try it. We put a 1960’s 5hp evinrude like yours on a 14’ canoe to use as a chase boat for duck hunting on a small river here, it would not push it upriver. Depending on how it is propped, it may or may not work. Make sure you have a way to get back if you take that on a river and it doesnt work, a big anchor and a cell phone to call a buddy.
Most of those old 3, 4, and 5hp motors were used as portable motors on small canoes.