Did you take apart the Reciever and the servos in the boat?

Crystals look like small metal cans with two prongs. They have the frequency printed on them, or paper tags listing the frequency.

They look like this
http://www2.towerhobbies.com/cgi-bin...al&FVPROFIL=++

Unless this is more of a "toy" boat in which the frequencies are sometimes hard wired into coils.