Re: Grounding Question
On fiberglass boat there really is no ground. The battery negative terminal is bonded to the engine block, and the engine block is generally bonded through various components of its gear case, propeller, and anodes to the sea. The battery negative bus is the most appropriate substitute for a ground.
In the case of radio antennas which require a ground to operate against, you would need to install a grounding plate or some other form of counterpoise. For a RADAR the ground is probably more for safety than for an enhancement to the antenna, so the battery negative terminal should suffice.
