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Author Topic:   Dual Batteries on Montauk 17
Feejer posted 04-08-2007 08:53 AM ET (US)   Profile for Feejer   Send Email to Feejer  
I realize this might be over kill, but have any of you put dual batteries on a Montauk 17? My electrical needs will be as follows. Combo GPF/FF, Icom VHF and Stereo with 2 speakers. In a perfect world I would have a starting battery and a house battery running thru a BEP combiner switch. Do I really need 2 batteries form my application?


jimh posted 04-08-2007 10:05 AM ET (US)     Profile for jimh  Send Email to jimh     
The basis for making a decision on electrical needs for a boat is not really influenced too much by the boat or the brand. The primary influence is the motor, and, since you have made no mention of the motor, it is hard to make a specific recommendation.

Speaking in general terms, the need for dual batteries depends on a boat's motor. If the motor cannot be easily started without a battery, it is a very good idea to have a back-up battery aboard. Some motors can be easily pull-started, but they may still need a battery to run. This is typical for many modern motors that have sophisticated engine electronic controls.

Another factor to consider is the availability of alternate means of propulsion. If you can row or paddle your boat easily, maybe you don't have quite as much worry about a lack of motor starting ability. Or if you never get more than 200-feet from the strand, you might not be as concerned. If you cannot row you boat back to shore, you need to have proper concern about engine starting.

The electrical load on a small recreational boat from its instrumentation and other electronic gadgets is not particularly high, and you can expect that the charging system of almost any outboard motor could keep up with the demand for current. About the only device that might be a power hog that I can think of is a big RADAR set. If you have a 10-kW radar running, it might draw some current from the battery. But a GPS receiver, a SONAR, and a VHF Marine Band radio with the squelch on do not draw much current.

The electrical devices on a small recreational boat that will draw significant current are electric motors. Electrical motors used for propulsion are very big consumers of electric current, and, because their use almost always implies that the main motor is not running, they tend to be operated during periods when there is no charging current available. Other electrical motors used to run pumps can also be a current drain, particularly a pump that is running continuously like a pump used to circulate sea water in a bait well.

Another current drain is vessel lighting. If you operate in periods of darkness and need to display your navigation lights or have a lot of other vessel lighting you will have significant drain.

Adding a second battery does not really create too much complexity in the electrical system. The extra cost is not excessive. The extra weight is not terrible, although all extra weight on a boat is a burden which reduces performance. Having two batteries does not guarantee you won't run them both down below the point of being able to start the engine, but, if properly managed, it does make that outcome less likely.

Feejer posted 04-08-2007 11:20 AM ET (US)     Profile for Feejer  Send Email to Feejer     
Thanks Jim
The motor is an 06 Mercury 90hp 4 stroke EFI which puts out 50 amps. I have no idea if this engine can be pull started or not. I will not have the boat for another 2 weeks. The Mercury will be the only means of propulsion. I'm sure 50 amps will be plenty to charge 2 batteries. On my last set up I had a Yamaha 150 which put out 35 amps. is what I used on that set up and it did a fine job. I guess my main question is not if I really need it, I think I can get along with out a second battery, but what type or room is it going to eat up in the console. I have always been some what of a pack rat when it comes to carrying extra parts on the boat. Tools, prop extra safety gear, etc... The Montauk has much less storage than I am use to and I will need to balance what I take and what I leave home.
WT posted 04-08-2007 12:32 PM ET (US)     Profile for WT  Send Email to WT     

Here's a picture of batteries in my 170 Montauk's console. It does eat up a lot of space but I suppose you could build a second story "loft" inside. I also use my ice chest/seat as storage. current=Montauk3-18-04001.jpg


jimh posted 04-08-2007 12:35 PM ET (US)     Profile for jimh  Send Email to jimh     
If the battery size is a concern, you can often get valve-regulated lead-acid sealed batteries which will be physically smaller than a conventional flooded-cell lead-acid battery of equivalent electrical capacity. In particular an absorbed glass mat battery or a gelled electrolyte battery will tend to give you more power in less space (and weight). However, expect to pay a premium for this feature, both in terms of the cost and in other areas of operation, such as sensitivity to charging voltage and tolerance of over-charging.

Also, if you stuff the battery in some hard to reach corner of the console and then pile 50-lbs of gear atop it, you may want to get a sealed battery to avoid problems related to checking the electrolyte level and out-gassing.

jimh posted 04-08-2007 12:43 PM ET (US)     Profile for jimh  Send Email to jimh     
Warren's very sharp digital image also shows an important component in a modern small boat electrical system: the on-board permanent battery charger. Because of the intermittent use of our boats and their storage on trailers, I find that it is quite handy to have an on-board charger wired into the battery system. I can plug the charger in for a few hour or over night before a boating trip, and I know I am going to get to the ramp with the battery system in excellent condition.

An intelligent charger will have a multi-stage charging cycle which will help to condition and maintain the batteries in the best possible chemical state to insure maximum available charge and longest life. Believe me, they will do a better job charging than some 1970's outboard motor's poorly regulated electrical output.

Then, on the other hand, there is the keep-it-simple approach: get a new WALMART battery every two years and carry jumper cables. That works, too.

Feejer posted 04-08-2007 02:51 PM ET (US)     Profile for Feejer  Send Email to Feejer     
All good ideas, thanks
Feejer posted 04-08-2007 02:54 PM ET (US)     Profile for Feejer  Send Email to Feejer     
I think for my first season of my Montauk I am going to go with a single battery set up and see how that works. I will also be carrying on of those self contained battery jumpers.
Chuck Tribolet posted 04-08-2007 08:51 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Warren: Where did you get those really cool red and black
wing nuts in the picture?


WT posted 04-09-2007 12:22 AM ET (US)     Profile for WT  Send Email to WT     

Sunny's Marine Electric 916-487-3868. Sunny installed all my electronics.


andygere posted 04-09-2007 01:02 PM ET (US)     Profile for andygere  Send Email to andygere     
I had dual batteries in my '79 Montauk. I used the boat in the ocean, and the charging system on the '79 Johnson was pretty weak, so dual batteries gave me a bit more confidence. Note that I would not suggest the location pictured for mounting the battery switch because it is subject to submersion if the boat gets even partially swamped.

I am using the BEP system on my current Outrage, and highly reccomend it. There are several threads in the archives on that topic. sitebuilderpictures/batteries.jpg

Teak Oil posted 04-14-2007 09:50 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
For what you are running there is no way you will need dual batteries. Unless you are going several miles offshore on a consistent basis I see no need for the complexity, weight, and waste of space just to run a couple of radios that a 1000 amp battery can run for days by itself.

A single 1000 amp battery will crank an engine for a LONG time. If you engine does not start by the time that battery dies, it won't matter if you have 50 batteries, there is something wrong with your engine.

The piece of mind offered by twin batteries is false IMO, unless you will be a long way from help or are running livewells, electric motors, etc. If you want true piece of mind, get a kicker motor.

Space on a Montauk is precious, you cannot afford to waste any.

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