Although interference is a risk , it is with ANY Rc project, engine type, being IC or Electric, with ANY type of radio, 40mhz, 27mhz or 2.4ghz. im not sure if changing the radio gear will be much different in your case, as a suggestion perhaps you should look at fail safes for your throttle should you have any radio glitches, or loss of signal, these little devices plug into the throttle servo and should you have a failure with the radio it forces the throttle shut, either killing the engine, or putting it to idle (how ever you decide to set it up).
With all IC driven items a fail safe should be a necessity for such events.
http://www.modelsport.co.uk/?CategoryID=9910&SubCategoryID=991035It is worth looking at changing your radio or at least purchasing the (or some) other sets of crystals for your radio (6 frequency's as standard and you have 6 others called splits) just in case others pop along and don't check frequency's, you could end up with a dead or uncontrollable boat.
2.4 ghz is the only way to eliminate this problem as they the radio gear is binded together so only your TX will work with your RX.
The choice is yours but they are the facts.