want to make RF remote control for model boat

Long range is range of few meters, kilometers, ....?

You need speed control, on / off, direction control ?

What motor type is in focus, and what power ?

i will control motors my self. just need signal, range must b around 100 meters.

Do you have some knowledge about electronics and RF?

If you just need signal, seems to be a bit thin description. Whatever you want, you probably know that you can buy ready made remote controls and receivers: http://www.hobby-lobby.com/car_boat_...rs_252_ctg.htm ?
If you need further RF related details, RX/TX design tips or plans, try to be very specific.