Rewiring a 16' Hewescraft - SailNet Community

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Old 05-23-2013
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Rewiring a 16' Hewescraft

My boat's wiring has been getting flakier and flakier so I decided to change things out. The mains switch was routed just to the engine. It took a hot lead from each battery in and the common out of the main switch went to the hot lead to the engine. The negative engine lead went to one battery ground and the grounds of both batteries were tied together.

That setup worked pretty well for the engine, but power for everything else was taken off just one of the batteries positive leads. That resulted in no ability to turn off everything and made all my accessory power being dependent on just that one battery. Another issue was where the switch was mounted. It was on the deck, underfoot... that positioned the connectors very close to the deck. I never saw issues when there was water on the deck, but it just never seemed like a good idea. I've found a new location for the switch. Up under cover and mounted to a side wall in the bilge.

My plan now is to route the accessory power off the mains switch common out. I bought a new mains switch yesterday, along with a 15' length of marine grade 8 gauge wire, some liquid tape, and a bunch of connectors.

So the only issue now is the ground that I supply to the front. I’m a little confused about how to do that. Currently, there is one 12 or 14 gauge hot wire that ran from the positive terminal of one battery and there were 3 smaller (14 or 16 gauge) wires connected to the negative terminal.

A friend suggested that I use the boat hull as ground. If I grok right, that would mean just running a wire that attaches to one of the major hunks of metal (probably a threaded stud and a ring connector would be pretty secure). But I’m confused about the circuit path at that point.

How are my batteries grounded in that scenario? I get the circuit path where current flows from the positive terminal, to a device, and back to the negative terminal. To complete the circuit I’ve described above, wouldn’t I have to connect my two negative battery terminals to the hull in order to complete the circuit? That seems like an odd way to do it to me; maybe dangerous, I'm in a little over my head at this point and looking for some "best practice" advice.

Looking forward to reliable power…. Soon

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Old 05-23-2013
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Re: Rewiring a 16' Hewescraft

I uploaded a simple diagram to try to make my question a little easier to parse.
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Old 05-24-2013
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Re: Rewiring a 16' Hewescraft

First, never make a metal hull part of a current carrying circuit - unless you want to see it corroded in a very short period of time. Your neighbors' won't be too happy either as their props and shafts disappear.

All grounds are common so with both batteries' negatives tied together run a wire to a bus where any other negatives are connected. I would keep the wiring at the battery posts to a minimum and run bilge pump negative as well as forward negative feed from here. The positive wires are better on buses as well which keeps batteries neater and easier to service.

I'm guessing your boat looks like the one pictured below.
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Living aboard in Victoria Harbour
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Old 05-27-2013
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Re: Rewiring a 16' Hewescraft

It sounds like you have a pretty good handle on what you need to do. It's interesting that this power boat has this two battery set-up. Note that many sailboaters go with an asymetrical set-up. One battery is the "main" battery used for starting and loads for normal use. The second battery is smaller and only used as a backup. For a given weight of batteries, this maximizes overall lifetime.

As for your ground questions, consider your boat circuits to just be a large flashlight - no need to tie to ground or the hull or anything else. There needs to be a path from positive, to the load, then to negative and that's it. That said, I would defer to someone who knew something about aluminum hull conventions. I would think you'd avoid any electrical connections to the hull, but there is a chance that your engine, which is tied to negative, is already tying your hull to negative.

I would buy a roll of duplex safety wire (two conductors) and run that everywhere. Get 14 or 16 awg for your main loads (assuming they are reasonable small) and perhaps 10 or 8awg for the run from the switch forward to your panel. If you want to do it all right, make sure you've got fuses in the right place (including on the battery positive terminals), and the best type of connections are adhesive lined heat shrink ring terminals and butt splices, but they're not cheap:

Battery fuse block:
Blue Sea Systems Terminal Fuse Block

Ancor Butt Connectors (Heat Shrink)

Ancor Marine Grade Flat Duplex Safety Electrical Cable
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