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ContinuousWave: Small Boat Electrical
Complete Overhaul of Electrical Power Distribution
|Author||Topic: Complete Overhaul of Electrical Power Distribution|
posted 05-04-2013 11:44 AM ET (US)
I am going to be installing Blue Sea System [electrical power components] and would like to make sure I have all of the necessary components. Thus far I have:
--two marine batteries
--Blue Sea 8-position 12-Volt switch panel
--Blue Sea Add-A-Batttery and [Automatic Combiner Relay] kit
--Blue Sea 12-fuse [secondary power distribution panel]
Do I need another Blue Sea System component? A grounding block?
posted 05-05-2013 08:55 AM ET (US)
A comprehensive list of components or device will be much longer. For starters, you will need:
--primary power distribution bus wiring accessories for positive and negative primary power distribution
--marine grade wire in various sizes with distinctive insulation colors
--ring terminal connectors for various wire gauges with various hole diameters
--crimp tooling to install the ring terminal connectors
--an assortment of in-line fuses for the recommended installation of the BLUE SEA SYSTEM automatic combiner relay; see the instructions. (By the way, these accessories cost more than the combiner relay.)
--insulated wire clamps to support the wiring
--an assortment of stainless steel pan head Phillip head self-tapping screws in various sizes and lengths to use as fasteners
The literature from BLUE SEA SYSTEMS should give you a good idea of the major components you will need and the accessories to go with them.
To discuss a complete overhaul of a boat's entire power distribution system, I would separate the complete overhaul of the boat's electrical system into smaller projects:
--battery selection and installation of battery cables to the primary power distribution, switching, bus bars, and over-current protection
--automatic charging relay or voltage sensitive relay installation
--secondary power distribution, control, and over-current protection
--branch circuit power distribution, control, and over-current protection
We could have a lively discussion on each of those topics.
posted 05-05-2013 10:19 PM ET (US)
[Separated from another discussion on a different topic and made into its own thread.]
posted 05-06-2013 08:45 AM ET (US)
BLUE SEA SYSTEMS makes so many components that it is best to identify them by their part number. For example, the component mentioned above as a "Blue Sea 12-fuse" secondary power distribution panel is most likely the BLUE SEA SYSTEM component PN5026:
This is an excellent blade fuse secondary power distribution panel. I have used that panel in the overhaul of my own boat's electrical power distribution. However, this is just one model of many models made by BLUE SEA SYSTEMS. Some other models do not have the negative power distribution bus or lack the cover. Because of the many variations, it is important to identify the specific model of BLUE SEA SYSTEMS component being discussed.
One important reminder: these fuse panels are supplied without any fuses. One must purchase the blade fuses separately. BLUE SEA SYSTEMS sells ATO blade fuses, but they are a bit pricey at more than $2 per fuse. I recommend sourcing the fuses from another vendor.
There are many manufacturers of ATO fuses, and many vendors offer ATO fuses without any brand identification. For an important component for over-current protection, I prefer to use a brand name device. I recommend using a well-known brand of fuses, in preference to a no-name or no-brand made-in-China fuse.
I give some more details about refurbishing the secondary power distribution on my Boston Whaler boat with the BLUE SEA SYSTEMS PN5026 blade fuse block with cover and negative bus in an article at
posted 05-06-2013 09:00 AM ET (US)
I am not certain what component you are referring to as a "grounding block."
In small boats with hulls of non-conductive material, such as a fiberglass boat, it was common with some manufacturers, notably Boston Whaler, to provide a bronze electrode on the transom that was installed below the normal water line level. This electrode was used as a ground for the metallic components of the boat's fuel system. The metallic components of the fuel system were bonded together in a daisy-chain manner of connection, typically using a 10-AWG conductor with green insulation.
If you are referring to an electrical bus with terminals or binding screws that is to be used to accumulate connections in power distribution or in grounding protection distribution, these devices are commonly used. They are available in a variety of configurations of different current rating, of different size terminal posts, and of different binding screw fastener size and number.
The need for these devices varies with the complexity of the power distribution. However, it would be very typical and very common to use several of these electrical bus distribution devices. In the BLUE SEA SYSTEMS product line, these devices are called BusBars. See
for a listing.
If one of these wiring devices were used in the connection of the bonding system, it may be a "grounding block."
More typically, these devices are used in the power distribution for aggregating the battery negative circuits onto a bus. They are more often used in the battery negative than in the battery positive because the positive circuits are usually distributed through power distribution panels with over-current protection for each branch circuit.
posted 05-06-2013 09:10 AM ET (US)
With boats, there is really no ground connection, and the sea is considered to be the ground. Connection to the sea is made by a dedicated electrode or by connecting to the chassis of an outboard motor which has exposed electrodes as part of a galvanic corrosion protection system. This bonding system should only be used for establishing a common potential between metallic components of the boat, and never for power distribution.
In boats with 12-Volt power systems the battery negative is wired with its own conductors and distribution system. This power distribution is kept completely separate from the ground or bonding system so that there are no circuit paths by which normal power can flow on the bonding system conductors. It is typically, however, for the chassis of the outboard engine to be used for the negative circuit for its power electrical system. Because the outboard engine is in contact with the sea through its underwater electrodes, the negative power distribution system is also maintained at "ground" potential in this way.
To emphasize the separation between the bonding system and the power system, the negative circuit of the power system is not referred to as "ground" but rather as battery negative.
posted 05-06-2013 09:00 PM ET (US)
I just re-did my Montauk power distribution this last weekend, I'll get a before and after picture posted shortly.
Aside from the major components listed you will need one DC fuse/breaker (~30-50 amps depending on what you need) that goes between the battery selection switch and the secondary power distribution (aka 12-fuse).
Or at least to ABYC guidelines, you'll need one. -- I actually did not install one, because the distribution panel is a mere 3" away and only has 5 circuits on it (lights, VHF, GPS, 12V, bilge). Bilge pump would be my biggest draw. I may add one later, but decided not to.
And do not know what console you are working, but the classic Montauk/Outrage are small, and very difficult to work in, so pre-mount as much as possible. -- Working inside the console added a whole day to the job for me.
posted 05-07-2013 09:02 AM ET (US)
From my article on the plant tour:
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