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Old 06-19-2013
ashmun ashmun is offline
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Re: Rewiring my sailboat

Hi Dauntless Brent,
Boat wire has some similarities to house and car wiring but also difference that are important. Unlike a car, where the negative wire can be grounded to a chassis, most wire in boats is 'round trip' (positive wire length and negative wire length running to a device, with a few exception like alternators or starters that are bolted and grounded on the engine). Unlike a house, boats wiring is subject to the marine environment (e.g. vibration, heat, moisture/water, and more). Corrosion is a big factor, so using quality marine wire, connectors and shrink tubing is import as is using the right tools. Good crimpers (as MikeOReilly pointed out) for battery cables are expensive, there is a small crimper that you can hit with a hammer or I'd suggest seeing if you could borrow or rent a big battery cable crimper. We've re-wired almost all of our previous boats, so we own a large crimper and love having it. Voltage meter and a clamp-on AC/DC amp meter is also useful. Remember to use both an ABYC E-11 compliant voltage drop and an ampacity table when figuring out the wire sizing. There tables are generally listed in marine electrical book, some marine cables sites, and there are app both on the web and for mobile devices but make sure they are ABYC E-11 and not housing 310.15 table. If batteries or the cables from the batteries to the switches, circuit protect, etc run through the engine room, remember to take this into account when using the table or an app. Engine space is warmer and the wire might need to be thicker.

There are plenty of good posts before this one, so the only three items I'd add is seconding the "check out Mainsail's site or tech tips" [not sure if this is Ed Sherman's Tech Tips that he's referring to, which is also a great site]; consider purchasing a few good marine electrical book (aka Nigel Calder, Charlie Wing, Ed Sherman, etc.), and even though good wire, connectors, circuit breakers, fuses and switches might seem expensive - get them because the consequences of not having good wires and circuit protection is more expensive.
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