RE: .61
61 you want to use a 11 by 7 prop i have had great speed with a 11 by 7 prop on mine got a brand new sc 61 ripped the engine mount off the hull lol got that much power
just looked at your engine nice you really want to use an 11 by 7 prop on it gives tons of power i tried a 12 by 8 got half the speed I have found
GRAUPNER 11 by 7s to be the best or 11 by 6 if you got 11 you can have the engine an inch lower than a 12