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Charging with Mercury 20EH / Battery questions

1117 Views 2 Replies 2 Participants Last post by  James_N
My skiff currently has a 2001 Mercury 20EH  2 stroke non tiller on it .I have read that the charging system on it is very minimal and i can't charge 2 batteries with it do to that.   
    Iam setting the boat up and have 2 batteries. A start battery at back of boat and then a deep cycle under the center console .  The deep cycle as its hooked up now to a fuse then switch panel to run  = nav lights , bilge , livewell pump ,fish finder , horn .

  I fish with live bait alot and thats where iam concerned .   Should i try to run just one battery and let the charging system do what it can  Or  Leave it the way it is ?

  Later down the road , i planned on looking for a used 35 or 40 hp outboard ( short shaft non tiller) if i can find one Would that allow me to run dual batteries to help ?
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· Brandon, FL
12,696 Posts
What is the output of the charging system? Is a larger setup available that is cheaper than a new motor?

If the output is less than 20 amps then you would be better off installing an isolator and charge each battery independent rather than in tandem.

· I Love!
34 Posts
Discussion Starter · #3 ·
Iam not sure where to even find out, I been told its 6 to 8 amps @ wot . Honestly , since i have not used the boat as of yet iam not sure how to even tell if it has a charging system on it ( other then the prev. owner saying it did. )

Iam stuck in the middle alittle on as to buy different boat motor or just replace this motor after the first of the year ... The other issue is this is a short shaft with a max of 40hp rating . . So i'll need to see if 30 to 40 hp charge output is enough to run dual batteries and look for that in a short shaft or switch to long shaft and a jack plate.
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