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Author Topic:   Necessity of a Battery Switch
swist posted 09-18-2005 07:30 AM ET (US)   Profile for swist   Send Email to swist  
My Montauk 170 did not come witha battery switch. What would be the reasons for wanting one? Just the security of knowing any electrical draw left on by accident is not an issue (save the bilge pump)?

And I have seen a couple of dual battery installations (with switch) on some Montauks. This strikes me as overkill for such a small boat, unless accessories are to be used extensively with the engine not running.

Any thoughts

jimh posted 09-18-2005 07:47 AM ET (US)     Profile for jimh  Send Email to jimh     
Many small boats do not have a battery switch. The parasitic current drain on the battery when all devices are switched off will usually be very small. As you mention, it is handy to have a master disconnect switch so you can easily isolate the battery from all loads.

A battery switch is a modest additional expense. A simple ON-OFF type switch is probably less than $30.

Typically the motor on a smaller boat can be pull started, so this removes some of the necessity for a back up battery for engine starting.

Bulldog posted 09-18-2005 08:05 AM ET (US)     Profile for Bulldog  Send Email to Bulldog     
Most small boats don't have battery switches and they do fine, a master switch for accesories other then bilge pump is a good idea on the dash. The downside of a battery switch mounted in an open boat near the stern is that it will get wet at times and corrosion never sleeps, the switch would be a possible high resistance connection and possible point of failure..............Jack
17 bodega posted 09-19-2005 05:39 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
This is on my "to do" list. Being berthed in saltwater lends itself to corroded connectors and IMO places a larger probability of current drain without a switch. With my boat, it's hard to tell if the salt and fog are the culprit or the old and sometimes tired wiring on my old boat. I have replaced many connectors, fuses and other terminals as well as sprayed the west marine corrosion inhibitor on all connections on the boat. I'll report back any improvements the on/off switch makes.
17 bodega posted 09-22-2005 11:03 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
I found out why my batteries were draining. It is not the necessity of a switch afterall. I was not previously aware that two sets of battery cables were connected by bolts and connectors until the outboard shop informed me. The positive lead had all but corroded away because the fitting was zinc and was not treated with anti corrosive agents. I replaced the leads, applied corrosive inhibitors, and pulled them back through... this will be more saltwater insurance in case of problems.

I will still install a switch, but don't feel the same sense of urgency.

Tollyfamily posted 09-29-2005 02:19 PM ET (US)     Profile for Tollyfamily  Send Email to Tollyfamily     
My Montauk battery will die in 3 weeks if not switched off. The Fishfinder and stereo still draw when off. I just pull the factory CB when parking, no need for a fancy shutoff.


Marsh posted 09-30-2005 09:50 AM ET (US)     Profile for Marsh  Send Email to Marsh     
Your reply may be the explanation for why my Montauk battery also dies after being parked for 3-4 weeks. It has only done this since I installed a GPS/sounder. Can you tell me: where is the "factory CB" on an '04 Montauk? Maybe I'll start pulling mine while I am parked as well.


swist posted 10-05-2005 06:52 AM ET (US)     Profile for swist  Send Email to swist     
I did install a battery switch after also observing that some of the elctronics draw power when off - I put it on the sloped part of the console inside front, just to port of the breaker box. The cables that used to go to the positive battery terminal had plenty of slack to reach the switch.

You need to buy/make a short piece of #2 red cable to go from the switch back to the battery.

The only slightly tricky thing was noting on the wiring diagram that the bilge pump positive feed does not go directly to the battery terminal, like on many other boats, but rather it hooks to the DC main via a short jumper inside the little breaker box. You need to get rid of the jumper, and then run a piece of #14 red wire from the bilge breaker to the #1 terminal in the battery switch (the side that goes to the battery). Otherwise you will switch the bilge pump off with everything else, which you probably don't want to do.

davej14 posted 10-15-2005 09:29 AM ET (US)     Profile for davej14  Send Email to davej14     
I found that the motor itself has parasitic leakage of several milliamps. This shouldn't drain a battery, but it all adds up. I am installing a switch before launching in the Spring.
jimh posted 10-15-2005 09:40 AM ET (US)     Profile for jimh  Send Email to jimh     
[Moved question about bilge pump wiring to a separate thread.]
Liteamorn posted 10-16-2005 11:00 AM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I installed a main switch just because I feel it is as important as life jackets.

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