Universal Diesel Engine – Wiring Harness Upgrade – Marine Wow!! On top of the trailer plug blunder a 10GA wire in a bundle like these wiring harnesses are in, and in an engine space, is not even rated to handle 50A of current under the ABYC safety standards. This wiring harness and alternator path was such an f’ing blunder from the start it’s not even laughable. Hardin Marine - Wiring Harnesses Terminal Block Style Marine Engine Wiring Harness - Big Block/Small Block Chevy Wiring your boat's engine can be simple and easy. Take the frustration out of bad connections. These weather proof correct fit engine harnesses make the perfect choice for a new boat or to update an old boat.