Don't bother running it on the hose. You need to set everything with the pressure that your pump makes, not the pressure that your hose makes. Just get the valve in, close it about 3/4 of the way, and go run it at the river.....if it runs hot, open it up....if it doesn't run hot...close it a bit more. You want enough water to keep the motor cool...no more than is necessary.
The problem with running the boat out of the water is that the thrust bearing in the front of the pump is only really "happy" and doing it's job when there is a thrust load applied to it. You can't apply a thrust load unless it's in the water. The thrust bearing not being thrusted combined with slop in the bowl bushings and imperfections as far as shaft/impeller runout goes can cause the impellor pilot to hit the wear ring and dick things up. Some people do it and get away with it, but try to minimize it.
Disconnecting the driveline on your float is a bitch.
