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ContinuousWave: Small Boat Electrical
Wiring Electronic Accessories
|Author||Topic: Wiring Electronic Accessories|
posted 02-26-2009 08:58 PM ET (US)
I am going to install a new depth sounder or fish finder on my 2006 Montauk. [D]o I need to wire it straight to the battery? Can I power it [through] one of the console switches? The same for a stereo down the road.
posted 02-26-2009 09:17 PM ET (US)
It is a bad practice to wire individual loads directly to the boat's battery. Generally there is a power distribution system built into the boat. Quality boat builders like Boston Whaler provide for enough capacity in the battery distribution system for attachment of new accessory electrical loads to the battery distribution panel.
If you wish you can use a console switch to control a branch circuit to which you can wire several electrical loads.
If you don't have enough capacity on the existing power distribution panel, you should add more capacity by adding a secondary power distribution panel.
The electrical load of a small depth sounder instrument will only be a few amperes, so there is probably enough capacity in the boat's existing power distribution panel to accommodate this load.
|Casco Bay Outrage||
posted 02-26-2009 11:24 PM ET (US)
Since the GPS, Sounder, Fishfinder and marine stereo's all come with their own power buttons, wire it to the positive and negative of the bus in the console with an inline fuse.
Consult page 12 of the 2006 Montauk owners manual found here to locate the two busses:
Many accessories come with wire and an in-line fuse already. As for the appropriate rated fuse, if not already included in the box, the specifications table of the manual will tell you what is correct.
posted 02-27-2009 09:49 AM ET (US)
I'd wire them to the accessory switch. That way you can
shut off all the electronics in one place. If you don't, by
and by you will forget something and flatten the battery.
posted 02-28-2009 08:39 AM ET (US)
And you also might forget to shut off the accessory switch.
I have always installed a battery switch so that any unintentional electrical loads, accesory or otherwise, will shut down. (Of course I could forget to turn off the battery switch :-) Then you can wire all accessories to the main power busses, which should allow for neater, more logical wiring, rather than piling up a bunch of positive feeds on the hot side of the accessory switch.
posted 02-28-2009 08:47 AM ET (US)
With regard to the 2006 Boston Whaler 170 MONTAUK in particular, I note that there seems to be a discrepancy between the schematic diagram shown in the owner's manual and the electrical panel layout illustration also shown in the manual. A switch with the legend STEREO is shown in the panel layout, but no such circuit is shown in the electrical diagram. The STEREO switch and associated circuit, if they exist, would be idea to use for control of an audio amplifier dedicated to reproduction of stereophonic audio recordings.
The base electrical system of a Boston Whaler 170 MONTAUK c.2006 appears to lack a primary battery switch, although one is offered as an option.
posted 03-01-2009 01:36 PM ET (US)
The addition of Blue Seas fuse panel(6 position) with negative buss to our 2003 170 Montauk solved the problem of too many wires on the battery or acc. switch. While installing the panel I added the Blue Seas 7650 battery switch and automatic charge relay. These additions really cleaned up under the console. Hope this helps.
posted 03-04-2009 07:15 PM ET (US)
Great photo. What is the top red wire connected to? Are you running three items off the panel? What are the items?
posted 03-05-2009 12:17 AM ET (US)
The suggestion to add a small auxiliary electrical distribution panel to boats like the Boston Whaler 170 MONTAUK which lack unused branch circuits for multiple accessory devices is a good recommendation. The cost of a small six-circuit expansion fuse panel is very modest. As the nice image linked above shows, there is ample room in most cases to install the distribution panel. Adding wiring to the secondary distribution panel in an organized and neat manner will improve the electrical installation on the boat.
By wiring a single device to each fuse you can select a fuse rating which is matched to the device. You can also eliminate in-line fuses in the device power cords. It is often seen that the in-line fuse holders are not particularly of the highest possible quality or especially suited for a marine environment. If you go with a one-to-one wiring, one device per each fuse, you can provide the same over-current protection to the device as the in-line fuse provided.
However, if you just add one device, I'd wire it to the accessory switch and let the expansion of the electrical distribution hold for the future.
|L H G||
posted 03-05-2009 01:26 AM ET (US)
Contrary to what JimH has said, for years back in the late 80's at least, both Lowrance Sonar and Raytheon Radio manufacturers always recommended that these devices have their own wiring directly to the battery. Their idea was to avoid static and other interferences. Following these instructions, when I rigged both my '86 and '89 Outrages I followed this practice. It is a pain to do, a lot of expense, and in re-wiring my later purchased old classics, I did not do this.
Several manufacturers even offered special battery connection terminals so that all these multiple power leads could be easily connected to the battery. I remember Bass Pro offering them.
posted 03-05-2009 08:49 AM ET (US)
The advice given in 1980 by manufacturers like Lowrance and Raytheon to connect their equipment directly to the battery was intended to reduce the potential for common mode noise in the power feed to those devices by isolating the wiring of device from any other loads. By wiring a device to the battery with its own individual power leads, the current flowing to and from the device will not share a current path with any other device. This means that noise induced on the power distribution of other devices cannot modulate the power being fed to the isolated device.
The concern I express is over the technique of making connection to the battery. It is a poor wiring practice to have multiple wires and terminal fittings attached under a single connection point like a battery post or a terminal block fastener. If four or five ring terminals are aggregated under a single fastener as a connection point, there is greater chance for loosening of the connection, especially on a boat where vibration is constant and high.
When the battery is wired to a proper distribution block using the proper size cables, the distribution block becomes the common point of the circuit, and the portion of the wiring on which shared currents flow is just the very large conductors which connect the distribution block to the battery.
Let's look at the electrical properties involved. In a 2006 Boston Whaler MONTAUK the battery is located in the center console. The battery is connected to the auxiliary power distribution panel by a conductor of 8-AWG size and a total of four feet (considering both positive and negative leads). We now compute the resistance of this portion of the circuit on which the common currents will flow.
The resistance of 8-AWG is .000739-ohms per foot. Four feet of 8-AWG will have a resistance of 0.002956-ohms. The typical radio or SONAR will draw no more than about 10-amperes of current. This means the voltage drop across our 8-AWG will be 0.02956-volts, which we can consider a common mode noise.
We then compare this with the noise induced into the power distribution by the connection of the outboard motor's alternator. The alternator output of the outboard motor contains a very strong AC component, equivalent to the difference between the battery voltage and the peak charging voltage. If we assume a c.1980 outboard in which there was little voltage regulation, the charging output of the alternator probably had a peak voltage output of 15.2-volts or more. We assume the battery terminal voltage was 13.2. This means the outboard motor is modulating the battery voltage with an swing of 2-volts of alternating current.
If we follow the 1980 advice we are going to connect our radio or SONAR directly to the battery so we will avoid a common mode noise of 0.02956 volts, but as soon as we start the outboard motor we will be glad to tolerate the power distribution having 2-volts of alternator noise imposed on it.
It seems to me that if the attached devices can operate in the presence of the 2-volts of alternator noise imposed on the system from the outboard, they will probably be able to tolerate the 0.02956 volts of noise imposed by sharing a few feet of 8-AWG wiring with other loads.
This analysis ignores any power line filtering which each device may have installed. As we have seen, the power source of a battery being charged by an outboard motor can be a somewhat dirty and noisy power source, and equipment manufacturers are aware of this. So they include power line decoupling and filtering components inside their device to reduce the impact of any power line noise on the operation of the device. Again, it seems very reasonable to me that if a device can operate properly with battery power while the battery is being charged by an outboard motor alternator, then it is very likely the device will be able to tolerate miniscule variations in the power created by sharing very small segments of the power distribution wiring.
However, feel free to run individual wires to the boat battery for every load in your boat if that is your preference.
posted 03-05-2009 09:03 AM ET (US)
Can the OEM bus bar of a 1988 Montauk be connected to the auxiliary power distribution panel? Or should the OEM bus bar be wired directly to the battery? The OEM bus bar would supply power to the navigation lights and auxiliary/courtesy lights.
Other items like a GPS device would be wired direct to the distribution panel.
posted 03-05-2009 11:16 AM ET (US)
If the load created by the devices connected to the bus bar doesn't exceed the capacity of the wire servicing the aux panel.
posted 03-05-2009 03:35 PM ET (US)
That makes sense. What would OEm navigation lights pull?
|L H G||
posted 03-06-2009 05:28 PM ET (US)
Jim - The information I used back in 1986 and 1989, and for subsequent replacement Sonar/Loran/GPS units, is still relevent.
Go to lowrance.com , download any of their Sonar/GPS manuals, and under the "power connection" chapters, you will see they STILL recommend connecting their units directly to the battery, with an in-line fuse near the battery (I put mine inside the battery case) and a power shut off switch to power plug corrosion at the unit.
They say you can use a buss bar connection, but it might give electrical interference.
posted 03-06-2009 08:03 PM ET (US)
I used the red/black positive/negative color scheme to keep it simple. The power portion of the distribution block is fed from the battery switch and the negative buss is picked up from the OEM buss bar.I disconnected every thing electronic from the battery and accessory switch and brought them to the fused panel. I terminated the VHF radio,Lowrance 337c and power for the NMEA backbone on the panel and last but not least the power to the ACR to drive the remote led. The picture was taken before the last item was wired in butit follows the same wire path as everything else.
posted 03-06-2009 10:02 PM ET (US)
Thank you. I purchased the same block and will wire this spring.
posted 03-15-2009 07:54 PM ET (US)
Would there be enough space on the Aux. switch for a finder, VHF, and stereo on my 2004 Montauk. The wiring under the boat is a mess. I'm adding a vhf and just want to make sure i have the space on the switch.
posted 03-16-2009 08:08 AM ET (US)
What the LOWRANCE manual says notwithstanding, I would not hesitate to install electrical accessories using power distribution wiring accessories of the proper size and capacity. This type of installation is universal where the electrical system is more complex than a rowboat.
posted 03-16-2009 07:01 PM ET (US)
JBG777, just run the aux switch to a terminal block and go
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