Is there a jet type motor available for model boats?

I am theorising on hull design for watercraft and would like to prototype several designs, with very limited funds. I am hoping to save money by utilising just one powerplant. I would also need details of specifications for ancillary items and radio control gear, servo motors for trim controls etc.

You would probably be better off building a catamaran type test bed and mounting test hulls in between the cat hulls with the power being provided by a motor on the cat. You might also build an upper hull that holds the radio, motor and steering controls and run the propellor and rudder out behind, changing the bottom configuration with add on sections.
A jet like is used in model airplanes will be rediculous on a boat – wants to run really fast and hard to throttle. A water jet might be appropriate, but I don’t know about miniature pressure pumps.
You can find servo info online. Most likely you will be able to buy a boat control, transmitter, receiver, servo package for under $100 and not have to worry about the details.