A lifetime of maintaining farm and heavy equipment out here in the wet…interspersed with over three decades of maintaining Army tactical vehicles used by young soldiers all over the world…have given me some strong opinions about vehicle electrics. These wiring harnesses reflect those opinions…. and the opinion that any small boat liable to be caught out in the ferry lanes in a fog bank needs to have minimal lights, horn and electric pump. Moreover, those lights, horn and pump need to be just as reliable 20 years from now as they are the day they were installed. I’m not a qualified electrician, and my opinions should be weighted accordingly…I’m just a lazy builder who never wants to have to mess with the electrics again once they are installed.



Marine wiring standards call for crimpled connections and protected terminal blocks like the older but professional installation shown above (that needs some maintenance). The books say that proper crimps and terminals have slightly less resistance than properly soldered splices and connections, and I don’t disagree….



…but what do you suppose the resistance is after several decades of user abuse? Add to that the fact that those bus bars are always hot, and invariably hard to get to in a small boat (or the panel the main aesthetic feature of the cuddy), and I’ll go with permanent, sealed connections every time. Crimped, soldered, greased, heat shrunk and armored.



Step One is to understand electricity. There are a few owner-type boat-wiring manuals out there, but the more general commercial manuals often provide the big picture a bit better. Other than the environment, the major difference between automotive and marine wiring is the ground…marine wiring must run a separate wire back to the negative battery terminal, which is the only ground on the boat. Automotive wiring generally grounds each fixture in place to the vehicle frame. Of course, marine harnesses generally require twice as many wires as automotive harnesses.



From the manuals, a plan for the harness is drawn. The amperage loads of each fixture and appliance are computed and the correct wire size selected from the tables in the manual. Then I generally up each circuit one wire size…anticipating somebody adding an appliance one day…. arrange them into circuits and select appropriate-sized switches and circuit breakers.



The necessary supplies are acquired and laid out for the job. I use tinned marine-grade wire almost exclusively…even in trucks and tractors. Ever have to do an emergency repair in the field only to discover the copper is too corroded to solder…even beneath the sheathing? Shown are 16ga, 14ga and 10ga marine wire in red for hot and white for ground. For economy, I generally use labels rather than multi-colored wires. Because I solder and heat shrink all connections, I’m not as fussy about crimp connectors, and use the standard electrical jobber fare (Tacoma Screw, Platt Electric and the like…generally higher quality than NAPA)…but if I were crimping without solder, I’d use all marine grade connectors.





Rather than crawl around for a couple days on bare frames in tight spots, I build the harness outside the boat. All fixtures are laid out in their permanent locations and the wire strung in place, allowing for vertical as well as horizontal runs once installed. I also try to allow a little extra length so the harness can be pulled away from the hull interior some day for repair. When building a boat from scratch, making and installing the basic harness before decking the boat will save a lot of bruises and claustrophobia.



For end-of-circuit wire connections to screw terminals, I generally fuse the strands with a tiny drop of solder to minimize surface area for corrosion to penetrate, and apply heat shrink tape to the ends (here not installed yet) for a good seal. The tip of the wire is lightly greased with proper dielectric grease (it does not conduct electricity…do not use automotive grease), the terminal screwed tight to the wire, and the entry points to the fixture coated with grease…and here protected with a rubber boot.

Continued…