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Author Topic:   Battery Recommendation
st posted 03-11-2006 01:40 PM ET (US)   Profile for st   Send Email to st  
I have two batteries interconnected with a PERKO OFF-1-BOTH-2 switch. BATTERY-1 is very weak; BATTERY-2 is getting weak. Even after 1.5-A trickle charge for two days last week, this morning the Mercury 90-HP motor on my 1982 MONTUAK will turn over only when I placed the swith to "ALL". The batteries are both size 24, deep cycle, and nearing four years old. I guess it's time for battery shopping.

My boat has minimal electronics, only fishfinder, no trolling motor. Should I replace them with the same deep cycle type battery? Should I use one starting and the other one dual purpose? Should I use dual purpose on both? What group size? 24?

I read an archive post someone recommending to not get group 24, "at least group 27, as heavy as you can handle it, and as big as you can stuff it in there." I am confuse now. Someone please simplify these selection, thanks!

Chuck Tribolet posted 03-11-2006 02:08 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I have a single Group 24 dual purpose and an Evinrude 90. It's fine.

The battery you start the motor with should be either a
starting battery or a dual purpose. The house battery should
be either a dual purpose or a deep cycle.

Before you replace the batteries, try a jumpstart from a
known good battery, attached at your batteries. If that
doesn't crank well, you have a wiring problem, not a battery

Also, 1.5 amps for 48 hours is 72 AmpHours. Group 24s are
usually about 60 amp-hours, BUT charging is not a 100%
efficient process, and chargers tend to be rated a bit
optimistically. I'd throw the better battery on the trickle
charger for week and try again.


jimh posted 03-11-2006 03:35 PM ET (US)     Profile for jimh  Send Email to jimh     
A marine dual-purpose battery is a good choice for a simple outboard boat that does not have sophisticated electrical distribution and charging circuitry. Unless you have special requirements, I would get two batteries of the same type.

My experience is that a Group-24 size battery is the proper fit in the OEM Boston Whaler battery box. Larger batteries will not fit very well.

Many mariners replace their engine starting batteries at routine intervals. Four years is a typical lifespan.

Batteries are sold in a wide range of prices. You can get a new marine grade dual-purpose battery for about $45 at discount retailers, or you can buy a premium marine battery for about $300. There is a lot of middle ground.

All of my current batteries are conventional wet cell lead-acid batteries. When I replace them I will investigate absorptive glass mat (AGM) batteries as an alternative.

st posted 03-11-2006 05:25 PM ET (US)     Profile for st  Send Email to st     
Thanks gentlemen for taking the time to respond and gave your valuable inputs. As per your suggestion Chuck, I went ahead and jumpered a known good battery to the boat battery, and it turned over the motor without hesitation.

Thanks for helping to simplify my options on batteries. if I may ask another, what's the advantage(s)-if any- for having a Dual Purpose type compared to a Starting type battery, if your primary need is only to start the motor? If this has been discussed before, please disregard...

glen e posted 03-11-2006 05:58 PM ET (US)     Profile for glen e  Send Email to glen e     
An AGM is the best battery for recreational marine purposes, IMO. Advatages:
no mainteeance
will take a regular charge
when depletyed, will "bounce back" faster
last longer

Cabellas makes AGM's that can be shipped UPS to you for about 15 bucks a batt. I have 3. The junk batts they gave me when I bought the boat came out immediately and these went in. The specs for a group 24 are amazing and they are dual purpose - they both can be used for starting and deep discharge purpose...

get them here.

Chuck Tribolet posted 03-11-2006 08:56 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The dual purpose battery will be more tolerant of being run
down than a starting battery. With electronics that you
might accidently leave on overnight, that's a good idea.

AGM batteries were developed for jet fighters that pull
negative G forces. If you take your whaler out in REALLY
snotty stuff they might be a good idea. I think that in most
cases they are overkill.

And I don't think they are any more tolerent of being run
down. Adm. Linda had one in her Suzuki 750. It lasted two
years, just like the flooded cell batteries she'd had before
that. The bike sat all winter, and the battery didn't like it.


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