Core Electrical System Revamp

1 Feb


This is a standard project for any sailboat older than thirty, for three reasons:

  1. Sailboats used to be built with electrical systems designed to power a VHF radio and a reading light, and now we ask them to power refrigeration, inverters, all kinds of electronic gizmos, and to charge the battery banks that supply them.
  2. Electrical stuff has come a long way in the last thirty years. Back then we had variations of automotive equipment, and now we have purpose-built, high capacity alternators and regulators, marine wire, and better distribution products.
  3. The thirty-year-old stuff is, well, thirty years old, and becomes suspect because of its age alone.

The corollary to this is the general electrical revamp: Over the years lots of electrical stuff gets added to a boat, and each addition contributes to what ends up being a wiring rat’s nest. At some point you’ve got to reign it all in! But we’ll leave the general revamp for later, and just focus on the core. By core I mean batteries, charging system, core cabling (the big stuff), battery switches, and engine electrics.

I had to do it on my old boat, and I’ve done it on a lot of other old boats: bigger battery capacity, bigger charging capacity, better gear…it just has to happen.

This particular project started with a fried starter on the engine…as in, burnt to a crisp, and very stinky, and then a second fried starter, indicating that it wasn't the starter's fault. 

New fried starter and new unfried starter

On the left is the new, fried starter. On the right is the new, unfried starter.

In troubleshooting the fried starter I saw that the entire output of the alternator went though a 12 gauge wire that made a circuitous route up to the instrument cluster in the cockpit, where it went through a cheesy amp meter, then back to the batteries.

This is the back of the panel, above, and this is where the whole output of the alternator passed:

This might not have been the end of the world, because it was probably only a 25-35 amp automotive alternator, but this is a long way to go (with the associated resistance in the wire, made worse by being old wire) and we have much more sophisticated amp meters now.

The owner, Captain Mike, has only had the boat for a few months. I asked him if he had ever charged his (now 400 amp hour bank, from four golf cart batteries) batteries at anchor using the alternator. He admitted he hadn’t, but he’s got plans to do the Pacific Cup and do some serious cruising afterwards, so he needs a good charging system.

We’ve added a Balmar 110 amp alternator, MaxCharge regulator, and all the associated cabling. The rule of thumb is that your alternator's charging capacity should be about a quarter of the total battery capacity, so for a 400 amp hour battery bank, we want a 100 amp alternator:

In sussing all this out, I found that all the wiring to the instrument cluster in the cockpit was not only pretty sad in general, but had several shorts and melted places, which I’m guessing is how two starters got fried. All the switches on the engine panel were suspect too. Here is the new panel, which I made out of a piece of black Starboard:

We also added an oil pressure and high water temperature idiot light. This addition has saved me a few times, because you probably won't happen to be looking at your oil pressure gauge when something ruptures and the contents of your oil sump get spewed all over your engine room, leaving your engine running strong…and dry. 

It’s a dirty little secret of engine manufacturers that the wiring harnesses they supply with marine engines are anything but marine. Namely, they often use just regular copper wire, instead of proper, tinned marine wire. Over time, this copper wire, crucial to the starting and monitoring of the marine engine, corrodes and weakens, and soon causes faults. Worse, on many of these wiring harnesses there is a big plug in the middle, where the panel plugs into the engine, so to speak, and these plugs inevitably get doused with salt water, corrode, and generally suck. Often just cutting out the plug and joining all the wires with waterproof butt connectors solves a lot of problems.

So on Captain Mike’s boat we’ve replaced and rebuilt all of the engine wiring with tinned wire, good crimps, and heat shrink tubing on all connections. We divided the batteries into two banks with an OFF-1-2-Both switch. We also added a starting relay: It’s a long way from the ignition key to the engine, about a 25-foot loop, so a solenoid starting relay will do well to preserve ship’s voltage going into the starter solenoid.

None of this stuff is cheap. The alternator/regulator package alone was about $900, and in case you haven't checked the price of copper wire lately, it's gone up with the prices of all metals.

The good news is that the old alternator, which still works and is internally regulated, will stick around as a spare.


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