Is it really necessary to put a hole in the bottom of the bucket to hook up to the raw water intake. If you just had a flexible hose connected to the raw water intake, couldn't you just stick it down into the bucket? I would think that the raw water pump would have enough head to pull the water out of the bucket without gravity's help.
Other idea that I had was to place a long rectangular Rubbermaid tub behind the boat under the exhaust flaps. Then run a flexible hose from the raw water intake, out, up, and over, down to the tub. This way you could re-circulate the water until the water started getting too hot. Anyone tried this? Should work if the raw water pump has enough head capacity.