Your not likely to be able to keep the water in your trash can with the prop on. Be careful not to over rev it. Get it running at the bench first. Carburetor running over – Turn the gas on for a minuet, then shut it off. Loosen the packing nut and back it out along with the fuel shutoff. Catch the fuel in a clean container or letting run it run on to a to a clean rag or fresh paper towel. Your looking for dirt. If you find some its explains why you carb is running over.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.