What diameter prop for 2s sport hydro?

[Andris Golts]

Hi all built a Dave Frank 21'' sport hydro the Miss Rock bare hull weight is 24 oz .Hull is set up with a Seaking 120 amp esc and a Leopard 2860 4050 kv motor powered by a single 7.4v 2500mah 50c lipo. What diameter prop would suite this set up and what length of run time can i expect ? Regards Andris Golts.

[photohoward1]

2500mah is not much. You need to keep your amp draw really low. I would start with a 435 maybe even a 432. Check it after 30 seconds.