small electric motor 140watt, size of prop and speed

[flowing]

Hi all.
I'm trying to build a small boat, but i'm not to shore of the power requirements. I would like the boat to beable to go over waves.
I'm guessing the weight of the boat to be about 5kg - 10kg.
The motor that I think might beable to move it out to sea is a 12volt 14amp max at 160rpm and 50kg/cm torque. Hydrodynamics of the boat should be quiet low(if you need I will try to find this info)

I would like to hear from you lot weather the motor fitted to a average to good prop would beable to move the boat over the waves.

Thanks for you time.

[Amp User]

Specifications:
Input Power Watts: 1,000
Output Power: 480 Watts (Comparable to 3 HP gas outboard)
Static Thrust: 68lbs.
Battery Output: 400 Watt Hours
Integrated Battery: Lithium-Manganese (13Ah@29.6V)
Steering Type: Twist tiller
Gearing: F-R continuously variable
Prop Size: 12" x 10"
Weight: 28lb.

[Amp User]

Specifications: Input power in watts
400

Rated voltage in volts
28.8

Final voltage in volts
33.2

Propulsive power in watts
180

Comparable gas outboards
(propulsive power)
1 hp

Comparable gas outboards (thrust)
2 hp

Maximum overall efficiency in %
45

Static thrust in lbs
33

Total weight in lbs
15.4

Weight of motor without battery in lbs
9.9

Weight of integrated battery in lbs
5.5

Shaft length in inches
17.7

Integrated battery
230 Wh LIMA

Propeller dimensions in inches
8 x 8

Propeller speed at full power in rpm
max. 1,200

Control
Remote throttle control

Steering
Provision for connection to kayak rudder; lockable

Tilting device
manual with grounding protection

Stepless forward/reverse drive
yes

[Guest625101138]

Originally Posted by flowing

Hi all.
I'm trying to build a small boat, but i'm not to shore of the power requirements. I would like the boat to beable to go over waves.
I'm guessing the weight of the boat to be about 5kg - 10kg.
The motor that I think might beable to move it out to sea is a 12volt 14amp max at 160rpm and 50kg/cm torque. Hydrodynamics of the boat should be quiet low(if you need I will try to find this info)

I would like to hear from you lot weather the motor fitted to a average to good prop would beable to move the boat over the waves.

Thanks for you time.

The boat in the linked clip is quite a bit heavier than you are planning. Total weight is around 110kg:
http://www.youtube.com/watch?v=GJedBprmSkk
The motor was working up to 200W in the video to get 11kph. It will do about 8kph with 140W. The motor is a model aircraft motor weighing 59g with a 12:1 reduction spinning a 15 X 12 model aircraft prop. The motor is rated around 600W but would not do that for very long.

You should have no trouble achieving planing speed with a 5 to 10kg boat using 140W. 160rpm is quite slow though. A prop pitched to get the speed potential would be unusual for the size of boat.

How fast were you hoping to get it up to?

Rick W