Look at the Dyno tests the TTpro 46 has more thrust than any standard 40/46 size engine on the market and it's cheep!
if your going to go with floats remember it takes a lot to break the suction when the plane trys to leave the water!
I would go with the 72 saito or a 60 two stroke.
my cub has a 72 OS fs and I think it works kinda hard to get up!
my 40 size Sea Master has a saito 72 and she comes up on plane fast and gets airborne with ease.