[lincpimp]

If you run that prop and a pair of good 2s lipos, say 5000mah 20-25c rated, the sight of it launching out of the water from a standstill will be enough for your boat friend. I ran a x448 prop once and it would launch the boat really hard, too much prop though, I had to mod the rudder just to make it fit. The x642 seems to be most people's choice for the boat. Only issue is that you will have to balance and sharpen the prop if you buy it raw, or pay out the rear to buy an already worked prop. Not really difficult, just tiime consuming.

Check out the offshoreelectrics.com forum and store, they have tons of info about boats, and the store owner, steven is very helpful, sort of like the Mike of brushless boats!