Hello zmajcek

Do you know what diameter propellor shaft you have? Is it 3.2mm or 5mm or something else?

To move the boat at scale speeds (20-25kph) you will need a motor with maybe 300 watts of power and a suitable ESC. You can find suitable brushed motors cheaply like the Traxxas Titan 775:

http://traxxas.com/products/parts/motors/titan775

but suitable brushed motor ESCs are becoming rare now and quite expensive. They are also sometimes not compatible with lipo batteries. Here is one that is that you may find on eBay:

http://traxxas.com/products/parts/escs/3019Revx2lvd



For a big boat you need high torque so I suggest a 36mm or 40mm diameter brushless motor with 1500kv or less to keep the motor rpm in the range of 20,000-25,000rpm with a 4S battery pack.

I would suggest something like this:

http://www.hobbyking.com/hobbyking/s...er_1025kv.html

It is high torque and has a cooling fan , but you could also add a water cooling coil or jacket if needed.

For an ESC I would recommend the Hobbywing Seaking 60A:

http://www.hobbywing.com/product_show.asp?id=223

Try Googling for a local supplier for you.

For a propellor, something like this is a good cheap option for a metal propellor, but it depends on the shaft diameter.

http://www.proboatmodels.com/Product...ProdID=PRB4019

There are also many plastic propellors available in the 40-50mm size which would give you some tuning options as well. Here are some examples:

http://www.offshoreelectrics.com/pro...d=ose-2bld-316


yellow-bird