To select the motor best suited for a hull it is important to know the hull size and amount of cells planned to be used. Size of hull will determine the size of motor needed to push the weight. Cell count will determine the wind (Kv) of motor needed.
Hulls from 20”/55cm – 34”/86cm typically will use a 540 size motor 36mm Diameter by 50-75mm length
Hulls from 34”/86cm – 40”/102cm + typically will use a motor with a diameter around or over 42mm and a length of over 65mm.
To determine the best suited Kv for a motor, the cell count planned to be used is needed. Following this chart will provide a wide-ranging base for proper kv selection.
|LiPo Cell||KV Range|
|2 cell LiPo||3000-5500Kv|
|3 cell LiPo||2000-3500kv|
|4 cell LiPo||1350-2700Kv|
|6 cell LiPo||900-1800Kv|
|8 cell LiPo||675-1350Kv|
|10 cell LiPo||550-1100Kv|
|12 cell LiPo||450-900Kv|
This is loosely based on an RPM range. This range is approximately 20 000RPM – 40 000RPM where approximately 30 000RPM is a decent standard for nearly all boat types. Anything higher than 40 000RPM may be considered to be a SAW(Straight-A-Way) setup.
If unsure about how to determine the RPM of a setup, please visit our RC Calculator page.
Hull/Motor quality effects on KV
A mono hull will run the Kv’s listed on the lower end of the range. (Larger Prop)
An outrigger type hull will run the Kv’s listed on the higher end of the range. (Smaller Prop)
A hull needs a certain amount of thrust to get on plane. Too much RPM will require a small prop which may not allow for enough thrust for the boat to get on plane. If a High RPM setup runs too large of a prop, excessive heat will be the result.
Higher Quality motors may run higher Kv within the range listed.
Lower Quality motors should run lower kv within the range listed.