I have seen Seniors fly from water with .40s all the way up to .91Four-strokes. A TT46 is a good motor and you should be able to fly just fine with it.
It is a myth that floatplanes need gobs more power. Full-size piper cubs carried floats around with only 65 hp. This one has a .45 and it would hover.

I don't remeber what the white one with the red stripes had for power.

If yours seems to be underpowered, you probably have those awful, heavy, oversize, built-up plywood floats. Get some nice light foam-core floats and go have fun.