What you have is a control line (U-control for some of the older generation) engine.

It does not need a carburetor to run, but it will only run at one speed- wide open! this is not a huge deal, other that your airboat will move along at the fastest speed the engine will pull it, with no way to slow it down. To use this engine on your airboat, you'll only need one servo to operate the rudder.

As far as starting it, you'll need to connect two lines from the engine to the fuel tank- one from the carb to the fuel pick-up line on the tank and one from the muffler pressure tap to the vent line on the fuel tank.

After you've filled the tank, put your finger over the exhaust outlet on the muffler and flip the prop over several times (WITHOUT THE GLOW PLUG CLIP ON) quickly to prime the fuel system- you should see the fuel run through the pick-up fuel line to the venturi nipple.

Once the system has been primed, connect the glow plug clip to the glow plug and quickly flip the propeller counter-clockwise. Make sure to use a 'chicken stick' or electric starter, and be sure to stay out of the way of the prop!