I have found most that recomend water pump are the ones selling water pumps. Clutch is only letting the boat sit stil at a idle. at a idle these engines do not over heat very fast. remember when you come to a idle the water jacket also has water in it that gives even more time to allow it to get hot. I like clutches and have used them for many years on many different builds and i never use pumps with no troubles. BUT you can drill mounting holes in your rails with no problems. you also have to put a fitting on your motor, many like them on manifold block between carb and motor.