Boat Trailer Wiring & Adapters | Wholesale Marine The light on the circuit tester quickly indicates which circuit is out- either tail lights, ground lights, or left or right turn signals so there’s no guesswork. If your trailer serves several purposes, towing your boat, RV, or camper, then you’ll need Anderson’s Boat Trailer Wiring Harness Adapter 7 to 4-Way. Boat Wiring Harness | Boat Wiring - Easy to Install Rewire Your Boat - Quickly and Correctly. Take days off your boat wiring project. Our snap-together boat wiring harness comes in three sizes for boats up to 30' and is designed to handle almost any boat wiring configuration - and there is no freight charge for purchases in the lower 48 states. Simply snaps to panels and parts - ours or yours! Harness Adaptors | Boat Wiring - Easy to Install - EzAcDc If you purchase the “snap together” option on our boat wiring harness, then the helm connection for the harness as a 12 position connector pre-installed and an adaptor comes with it. The snap together harness also includes snap together connectors for all of the accessories, adaptors, and tie wraps.