Sugggest you look at Flysky i6. I have been using this for over a year now for both sailing and airplanes. It is a 6 channel computer 2.4 radio which is an over kill for your 2 channel boats but is very reasonably price at about $50 US. Try banggood.com
Art
An advantage of the I6S is the receiver battery voltage is transmitted back tot he transmitter so you always know how your receiver is doing. And it is sold by various names, i.e. Hobby King has a version and it comes with 2 receivers.