Network connectors reliable for marine use?Jan 1, 2003
From Ocean Navigator #126 November/December 2002
All boaters should be aware of the potential problems in using equipment with RJ-45-style connectors in a marine environment. These connectors were designed for a benign office environment, and are prone to failure due to both vibration and corrosion. Due to the mechanical design of these connectors, vibration in either the cable or the receptacle is transmitted to the gold-plated contact pins. This wears away the gold plating, eventually resulting in a poor electrical connection. Not being sealed connectors, salt-laden air will quickly corrode the pins.
Wherever possible, electrical connections on a boat should be made either with sealed marine-grade connectors or with direct, sealed wire-to-wire connections, such as lugs and terminal blocks. A number of companies have started making industrial-grade RJ-45 connectors, but few marine-electronics manufacturers have incorporated them into their products to date.
If given the option of choosing equivalent shipboard equipment with RJ-45 connectors or other more ruggedized connectors, boaters should always go with the latter. RJ-45 connectors may be outstandingly easy to install, but they should be avoided unless they can be isolated from both vibration and ambient air.
Bruce Butler lives in Maple Ridge, British Columbia, and is a professional engineer, with 15 years of experience designing undersea vehicle systems and boat electrical systems.
Chuck Husick responds:
Perhaps I have been fortunate since my Tecnautic autopilot, using the RJ-45 system, has performed flawlessly ever since installation almost two years ago. The system is installed in the port cockpit cuddy on my boat, where it is reasonably protected from direct exposure to intense salt spray. However, it is often operating in a saturated environment, made especially difficult by the very high temperatures we have here in St. Petersburg, Fla. I added some DC4 compound to connector cavity as a precaution, and I believe the manufacturer is recommending this procedure for all installations. Vibration does not appear to be a significant problem on most boats, although it might be of considerable concern in on-engine applications.
I recently completed the installation of a system comprising a Furuno 1833C radar/sounder/chart-plotter, Tecnautic autopilot/hull-speed/wind-velocity system plus VHF/DSC radio and Furuno Navtex receiver. That system employed a wide variety of connectors, including some designed for use in exposed locations. So long as the cables could be used without removing the connector, everything went smoothly. Splicing or trying to reinstall a connector that had to be removed to facilitate the installation was another matter entirely. A large part of the problem stems from the use of very small wire gauges, occasionally less than No. 22. Working with wire this size can be very frustrating in a boat environment.
I agree that normal RJ-45 connectors are not suitable for use in exposed locations; however, they do seem to work well in behind-the-panel applications. The ability to install new terminals using a readily available crimping tool is a real advantage, especially when working in a cockpit seat locker or similar environment. I used to design electronic computers and was used to using the then-standard 2- to 4-inch-diameter AN connectors. I must admit that I occasionally long for them, along with the No. 16 and No. 18 wire we had to use in those long-gone days. During my time in the aviation industry, we used almost every kind of connector on the market, with the ultimate realization that if a failure occurs in an electrical or electronic system, you should look at the connectors first!
I have used marine-grade butt connectors in splicing radar cables and have also used small terminal blocks in that application. They work, but not all that well from an installation standpoint. I have found that even the water-resistant connectors used by first-class manufacturers are far from really waterproof. From my viewpoint, the fact that the RJ-45 performs well as the standard connector for almost all Ethernet systems speaks well for the overall concept and the quality achieved by reputable manufacturers. If I were asked to design a connector system for use in protected areas of a boat, I would use the RJ-45 without concern. In places such as exposed on-deck areas, or in or near the bilge, a heat-shrink-tubing-enclosed butt splice is most likely to survive.