Does a ’56 3 hp Johnson have a tell tale, or does the pumped water exit under water with the exhaust? If so, should the water come out as soon as motor is started.
If you look at the front of the midsection, right below the transom mounts, you will see a small square piece with a screw in the middle of it. This is the exhaust relief and the water will come out here. Don’t expect a strong stream as it just dribbles or sprays out and can be hard to see. It should start coming out shortly after startup.