Hi John,
I'm certainly not a specialist on powerboats but the model is about only about 2ft long and the displacement is only going to be about 2 -2.5 lbs if its anywhere near scale. The recommended prop is 35mm which would indicate about 35mm outrunner brushless (The 600 motors are 36mm diameter). You've probably only enough displacement for a 2S (7.4 volt) Lipo or a 7.2 volt NiMh battery, so possibly about 1300Kv would fit the bill? These are only gut feelings and others would give better input and it also depends how you drive?