FE motor selections

[waterotter]

Can anyone help me understand the motor selection process.
1) kv/rpm per volt, is it better for higher or lower kv?
2) Whats better for 1/8th scale and 1/13th scale hydros?
3) What do I look for when selecting a motor, rpm vs torque vs kv?
4) How do I know how many cells is required to run any particular motor.

[Diesel6401]

Can anyone help me understand the motor selection process.
1) kv/rpm per volt, is it better for higher or lower kv?
2) Whats better for 1/8th scale and 1/13th scale hydros?
3) What do I look for when selecting a motor, rpm vs torque vs kv?
4) How do I know how many cells is required to run any particular motor.

1) Depends on size of boat. Smaller boats typically higher kv and lower voltage
2) Bigger boats should have lower kv motors and more voltage. They can handle the weight better and swing a large prop that have a lot of torque, but make up the rpm difference by the prop they use.
3) Once again depends on size of boat, higher kv motors are mostly all top lend ow voltage higher amp pull and can not handle a very large prop, low kv all torque high voltage low amp draw and huge props
4) once again depends on size of the boat and type of motor best suited for that hull. Once you figure which motor will work best then match the number of cells required to reach your desired RPM

RPM = Voltage x KV

RPM range should be between for fun should be under 30k total rpm should not exceed 40,000

[waterotter]

Basically I'll be building 2 boats, a 1/8th scale hydro based on cybercrxt frame kit and a 1/13th scale hydro based on Garry Finlay's Atlas Van Lines.
For the 1/8th hydro I was going to use the Leopard 5692 1342kv with 2 4s1p 5000amh packs in series.
For the 1/13th hydro I was going to use the Feigao 540XL 3324kv with 2 2s1p 5000amh packs in series.
Are these a good choice and are they legal for racing?

[waterotter]

BTW the Lipo's would be 20c discharge, I think the 30+ has lower run times.

[video200]

sinse you wil be racing i wont comment on your motor choises.
but the more C your battery have the better.
boats are amp hogs and if you have 30c batteries you wil apritiate that in the long run.

just my kr 0,2