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Author Topic:   Starting Battery Specifically for Mercury OptiMax Outboard
csj posted 10-01-2010 10:28 AM ET (US)   Profile for csj   Send Email to csj  
Folks, I have been told I need two batteries [with a rating of 1,000-cold-cranking amperes] for my twin 135-HP [Mercury OptiMax] motors on a [Boston Whaler CONQUEST]. Is this accurate? Do [the starting batteries needed for Mercury OptiMax ] need to be deep cycle batteries? Any suggestions [for a starting battery for a Mercury OptiMax on a Boston Whaler CONQUEST]?
K Albus posted 10-01-2010 12:09 PM ET (US)     Profile for K Albus  Send Email to K Albus     
Based on your profile, I'm guessing your Optimax 135s are 1999s. If that's the case, I believe you need batteries with 1,000 marine cranking amps (as opposed to cold cranking amps). It is also my understanding that the batteries should be starting batteries, and not deep cycle batteries.
Lil Whaler Lover posted 10-01-2010 04:04 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
Deep cycle batteries generally have much lower cranking power. DEKA DC27 (deep cycle) has 715 CA'S @ 32 degrees, while the DEKA 27M6 (combo) has 1050 CA'S @ 32 degrees. This is fairly typical of the breed. The 27M6 was jointly developed by DEKA, Yamaha and Gray White. All Grady's come standard from the factory with the 27M6 installed.
Mambo Minnow posted 10-01-2010 07:35 PM ET (US)     Profile for Mambo Minnow  Send Email to Mambo Minnow     
Yes, starting batteries at 1000 MCA. West Marine has them. They are the ones in a white plastic case. Approximately $105 ea.
jimh posted 10-02-2010 08:07 PM ET (US)     Profile for jimh  Send Email to jimh     

jimh posted 10-04-2010 07:58 AM ET (US)     Profile for jimh  Send Email to jimh     
The best source of information about the proper battery for starting your engine is from the owner's manual. The owner's manual will have the recommended minimum battery characteristics needed to start the engine. It is generally better to conform to the manufacturer's specifications than to go by what you've been told by others.

It is typical for a Mercury OptiMax outboard to require a starting battery that has a marine cranking ampere rating of 1,000-amperes. A battery with a rating of 1,000-MCA may be found in a deep-cycle battery design.

In a Group-24 size, the INTERSTATE BATTERIES model 24M-XHD is rated at 1,000-MCA. It is not a deep-cycle battery.

On your particular boat you may find that the primary electrical distribution is split between the engine and the house loads, and you may want to use a battery for each load that is more specific for the load. There is no reason to use a deep-cycle battery for engine starting, but deep-cycle batteries can give longer life in services where they will be discharged and re-charged over many cycles.

jimh posted 10-04-2010 08:00 AM ET (US)     Profile for jimh  Send Email to jimh     
Whether or not you need two batteries is more a matter of how much reliability you want in your electrical system. If you cannot start your outboard motor by pull starting, you likely will want two batteries to provide more reliability for electrical engine starting.
themclos posted 10-04-2010 10:08 AM ET (US)     Profile for themclos  Send Email to themclos     
I would recommend you investigate a Sears Diehard Marine Battery, either the Platinum PM-1 or PM-2. They are AGM batteries and I believe either one will meet the requirements for an Optimax outboard motor.

I have the PM-1, Group Size 31M, and it has performed very well.


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