I'm running a APC 17 X 8 prop. (do not use a wood prop. The water chews it up.) I've had the Cub for 2 years and have about 5 hours on the engine. I hand flip for starting. I only fly it 2-3 times a year so after setting for a long time it takes about 6-8 flips with choke on till it pops, then 3-4 flips with choke off and it starts. When the engine is restarted on the same day it starts much quicker. For me the whole thing about the Cub is landing and taking off on water. If it didn't have floats I wouldn't have it.
Caution.... Cubs do not like wind especially mine because of the full wing. Its easy to flip over in winds above 10 MPH.

Hope this was of some help.
Have fun

K.O.