Technical Article: #009

Title: Hustler Rewire Part 1 – Considerations and Planning
Date Added: 14th October 2012
Article Author: Andy
Hustler 30 – Hariette B
Rewiring a boat is no task to undertake lightly.  It can be a very complex task and many different things need to be taken into account.  This article is intended to share my experience.  Hopefully it’ll help other Hustler owners when considering rewiring or even just adding a new electrical component to their boats. To cover this in one article isn’t practical so I’ll be splitting my experience over a number of articles namely:

Rewire Part 1 – Considerations and Planning
Rewire Part 2 – The Tools, Rewire and Battery installation
Rewire Part 3 – Installing a Sterling Pro Split-R
Rewire Part 4 – Installing a Solar Charger
Rewire Part 5 – Installing a new Stereo

Firs of all I want to be clear that I’m no expert! What I impart here is my experience based on gleaning things from books, the net and my own experience with 12V electrics over the years.  If you are looking for a guaranteed installation then pay for a professional to come in and do the job especially if you aren’t confident in working on your own boat. However, you own a Hustler and I’m assuming as a Hustler owner you aren’t afraid to get involved and do most repairs and upgrades yourself. In which case these articles may help expand your knowledge a little bit more.

Original installation – No battery straps, no controlled wiring, no idea!!!

I chose to do this myself because as skipper of my ship I wanted to be sure of what’s going on with my boat, how to fix it and also save some cash in the process :-). Seriously though should I lose power and have problems with my electrics at sea I wanted to be sure that as skipper I’d know exactly what was happening and most important of all why.

In the beginning…
Hariette B is the typical 70’s boat.  There’s no wiring diagram, no channels for neat wiring and certainly no consideration for today’s power demands when afloat.  In short much of what’s as standard within your boat from the 70’s and even the 80’s is far from what’s required of today’s power demands.  This worried me as I wasn’t sure whether Hariette B’s wiring was up to the job for my demands as I’d read all sorts of horror stories of cable overheating, getting hot and in extreme cases bursting into flames!!!

I simply had to check what my wiring was like before the new season. Not only that if there were any issues afloat I’d know how to deal with them. So I did some research on 12v electrics and what was needed.  There’s a few books that are very namely:

Practical Boat Owner’s Electrics Afloat: A Complete Step by Step Guide for Boat Owners
The 12 volt doctors handbook (which you can download from here)

There are others out there and a multitude of websites that cover the subjects but I found I kept coming back to these books to cover the principles and to help aid my understanding of the 12v electrics system.

NOTE: The 12 volt doctors handbook has some old info in there. Some of it still applies. However, the connecting wires bit is a little outdated nowadays.

From this point on the articles will assume you know what amps, volts etc. all mean and have a basic understanding of the 12volt system. If you don’t, click on the eBook link above to download it to learn the principles.

It’s all in the planning
Before undertaking any rewire I needed a plan.  I needed to know exactly what I want from my electrics, how often I’d need them on. From there work I’d also need to calculate not just the loads on the wiring but the batteries too.  I only had two batteries one for starting and one for house.  I knew this wasn’t enough.  In addition, it appeared the only charging that took place was when the engine was on. All well and good but what if I wanted to sail for 20+ hours?  What if I was at anchor for a few days?  How would I know my charging was efficient?  I had a manual battery switch.  This meant that I’d need to remember to switch from Battery one to Battery two physically in order to charge the batteries (If I remembered that is).


The original Battery switch – Check out the lovely wiring job.

There are better solutions out there for charging. However, I just wanted something simple and this was to be found in the guise of the Sterling Pro Split R. What does it do? This device does away with the manual battery switch and automatically charges the batteries when the engine is running from your existing Alternator. It prioritises the Starter battery first for charging then the house batteries. As it tops up the starter it slowly increases the charge to the house batteries. I’ve tested it all season and I can honestly say it’s been brilliant. However, more on this in Part 3! I wanted to run the following in Hariette B:-

  • Usual Instruments (GPS repeater, Depth, Radio)
  • Chart Plotter
  • Auto Pilot (Raymarine 2000+)
  • Stereo
  • Nav lights
  • Interior lights
  • Eventually a Diesel Heater (Webber/Eberspacher)
  • Power Monitor

I tried to think as much as possible of everything I’d want to run electrically as I needed to do a power audit.  If I knew how much I needed to run at a given length of time with the appropriate amps I’d know:

  1. How much battery capacity I’d need
  2. The gauge of wire I’d need to buy for charging and running the system
  3. The length of cable I’d need as the longer and thinner the cable the greater the likelihood of voltage drop

My calculator is a simple spreadsheet and just for you it’s available for download here :-). The spreadsheet gives the total number of amps per hour.  You can then deduct this from the total amount of amps available to your battery.  To make things easier though I added extra columns to calculate hours run time for a typical 24 hour period at sea.

The example assumes I’ve sailed for 8 hours then anchored overnight. The chart plotter is my anchor drag alarm so always on. I’ve also assumed I’ve got a boat heater and this is switched on towards the end of the evening. I’ve got all my interior lights burning for 8 hours, played some music on the stereo and I’ve had the fridge on for 3 hours. Normally you’d have some engine on if you were leaving a marina or even an anchorage so there would be some charge. However, this assumes no charge at all as a worst case scenario. In this scenario for me I’d have to switch my engine on after 24hours to charge up the batteries. If I added a third battery I could leave it longer.

I’ve also added the battery banks calculator so the results from your audit can be easily seen.  I was originally going to go for 3 house batteries but only have space for two.  To make matters worse I only have a small space batteries so I needed small high capacity batteries (Not that easy to find). The calculator also allows you to factor this into your total calculation.

Remember: A battery can never be run down to zero.  If you have a hundred amp battery the safest you can drain it to is by around seventy percent.  This means with a hundred amp battery you only have seventy amps available.  As soon I as understood this it changed everything as to what was feasible!

Mapping it all out
So now I had it figured out as to why and what I wanted to run the next thing to figure out is how.  This can only be visualised by drawing a diagram of what you intend to install and how it’s all routed. This is where existing wiring diagrams can help you to understand what you boat looks like and where the wires are routed.  However, I think you will need to be extremely lucky to have a wiring diagram for a Hustler (Hopefully maybe an owner out there has one, If so please contact me).

In my case I had to start from scratch and put my own diagram together.  This diagram would take into account not just the items I wanted to run but the new components I’d need to charge the batteries and reduce the load on the wiring overall.

The new components were:

  • Second switch panel to handle the instruments separately from the lights
  • BUS bars to handle the distribution of power negative and positive cable runs
  • Solar Panel for keeping the batteries topped up when I’m away or just pottering around under sail
  • Smart battery charger to charge the starter and house batteries automatically so I don’t need to worry about that manual switch ever again
  • Automatic Bilge Pump
  • Fuses! I needed fuses all over the place.  It’s amazing how there weren’t any anywhere!

In addition there’s the existing wiring.  I pulled everything out to explore what was going on with the wiring, where it was and how old it all was.  This will be explained in part 2.

My wiring diagram can be seen below. It is also available to download here as a high resolution version.

Hustler Wiring Diagram

Please think of this as an example as you’ll need to draw your own to make sure it’s fit for your requirements.  Of course if you have an identical set up to me then you are in luck!

Some Notes…
1) Yes, I know it’s not a true wiring diagram as it’s a mixture of symbols and images. However, I thought this approach made it easier to understand.

2) Yes, I also know it doesn’t go into the minutiae of the lighting circuits but to be honest, life’s too short and it’s pretty obvious where the lighting circuits are as it’s a common negative and a unique positive for each light back to my positive Bus Bar.  I know this therefore my diagram serves the purpose to show the overall big picture.

3) I used Visio to create my final diagram. However, I sketched it all out before I put it into Visio just to double check things were ok.

4) Double check everything, my diagram may not be right for your installation. Use it purely as an example.

For anybody about to start this task do not underestimate the cost in time, tools and money.  The more you think about the planning, the cable runs, the placement of new components and most important of all the battery load and placement the easier the job will be to actually do.

I think I spent 2-3 months poring over electrical manuals, catalogues and downloaded all the manuals for all the instruments I use in order to build the right view of what was needed. This enabled me to buy the necessary tools and the necessary wire for the job.  Having planned everything fully the installation was completed over a few weekends. I’ll never forget the look on my wifes face when I had all the fittings out of the boat and stripping out all the wires :-) more on this next time.

Next is part 2 – The Tools, The rewire and Battery installation

The article above is related to works that the author has carried out to their own boat at their own risk. This article is intended to share the authors experience with other readers only. It is not intended to be a comprehensive step by step instruction guide. Anyone choosing to do any work as a result of reading this article do so at their own risk. If there is any doubt about whether to conduct work on your own boat call a professional to assist.