Can my Merc 125 handle charging two batteries?

tomxdana

Seaman
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Oct 16, 2007
Messages
63
I have a trophy 1802 with a Merc Saltwater series 125 outboard uses a stator and not an alternator. It says that it produces 17 amps at WOT. Is this enough to charge two batteries? I have 2 now and I'm looking to replace them because they are 5 years old and they don't hold charge as well as I would like. Can I go to 27 series batteris? I believe they are 24 series right now. If the motor can't handle charging the bigger battery it might actually be worse than a waste of money. Thanks for any input. My trips are usually within 5-8 miles of my marina so I don't get a lot of run time to charge. There is a nowake zone so I guess its running for 20-30 mins to get to fishing grounds.
 

ondarvr

Supreme Mariner
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Apr 6, 2005
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11,527
Re: Can my Merc 125 handle charging two batteries?

It won't charge them quickly, but it will charge them. Bigger is almost always better when it comes to batteries.
 

fishrdan

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Jan 25, 2008
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Re: Can my Merc 125 handle charging two batteries?

produces 17 amps at WOT.

My trips are usually within 5-8 miles of my marina so I don't get a lot of run time to charge. There is a nowake zone so I guess its running for 20-30 mins to get to fishing grounds.

What is running off the batteries and how much do they get discharged on a trip, do the batteries get heavily depleted?
17 amps at WOT isn't going to charge the batts much, but if you are only recharging for starting the outboard and light electronics draw it might work fine.

Leaving batteries in a discharged (or not completely charged) state will shorten their life, but if you got 5 years out of your current batteries, I'd say the batts and outboard's charging system did very well.

I'm with ondarvr, that bigger is better for batteries, but what are you using the batteries for? Starting and electronics with a backup battery, or start battery and trolling motor battery, something else?
 

fishrdan

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Re: Can my Merc 125 handle charging two batteries?

duplicate post
 
Last edited:

tomxdana

Seaman
Joined
Oct 16, 2007
Messages
63
Re: Can my Merc 125 handle charging two batteries?

What is running off the batteries and how much do they get discharged on a trip, do the batteries get heavily depleted?
17 amps at WOT isn't going to charge the batts much, but if you are only recharging for starting the outboard and light electronics draw it might work fine.

Leaving batteries in a discharged (or not completely charged) state will shorten their life, but if you got 5 years out of your current batteries, I'd say the batts and outboard's charging system did very well.

I'm with ondarvr, that bigger is better for batteries, but what are you using the batteries for? Starting and electronics with a backup battery, or start battery and trolling motor battery, something else?


Because my boat doesn't have a self bailing deck, any water that hits it ends up in the bilge. I slip it from April to Dec and I don't have any electricity at the dock. I have the batteries isolated with the Blue Sea system so I have one for the motor and the other for electronics. My main bilge is off the "house" battery and then I have another pump a little higher as a backup that connects to the "start" battery. Running my gps drags the voltage down so I rarely even keep that on. I have a radio but haven't used it mostly because I like the quiet when I'm fishing but partly because of the battery situation. No trolling motor or hose for the deck.
 
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