Wiring to Connect 5-Flat on Trailer and 4-Round on Boat to 5-Flat on Tow Vehicle

Updated 08/21/2014 | Published 08/19/2014

Products Featured in This Question

RoadMaster 4-Wire Connectors - Trailer and Vehicle Ends

(50)

$14.22

16 Gauge, 4 Conductor Jacketed Wire - Per Foot

(237)

$2.82

Deka Heat Shrink Butt Connector - 12-10 Gauge - Nylon Insulation - Yellow - Qty 5

(1104)

$8.13

Hook Probe Circuit Tester

(61)

$13.33

Question:

I have a boat with a 4-pin round connector in the bow to engage built-in boat transom lights when the vehicle brakes. The vehicle end connector is a 5-pin flat. I am looking for a way to split the 5-pin flat from the vehicle to connect to the 5-pin trailer connection AND the 4-pin round connector in the bow. The boat manufacturers part is $$$$$. I have checked the trailer section on your website but do not see a solution ........ any ideas? Thank you.

asked by: Rick M

Expert Reply:

Although we do not carry a wiring harness/adapter that will allow you to split the 5-flat on your tow vehicle to allow you to connect to both the 5-flat on the trailer and the 4-round on the boat, I have a solution for you.

You will need the RoadMaster 4-Wire Connectors, # RM-910030-4, Jacketed 4-Wire (sold by the foot), # DW03240-1, and the Deka Heat Shrink Butt Connectors, # DW05745-5.

I recommend that you splice into the wiring, behind the 5-flat on your trailer, in order to add the 4-round. You will want to start by checking the pin functions on the 4-round on the boat using a circuit tester like part # PTW2993. Depending on which end that you need, you will wire the 4-round trailer or vehicle end using the jacketed 4 wire and connect those wires to the like function on the 5-flat wiring on the trailer with the Deka Heat Shrink Butt Connectors, # DW05745-5. Lastly, I recommend wrapping all of the wiring connections with electrical tape and you should be ready to go.