12v trolling motor on 24v setup

[mn_bowhunter]

I want to add a transom mount trolling motor and have a 24v bow mount.  My 3rd battery runs the other electronics including starting so I don't want to run that down.  I'm worried that if I run my 12v troller to one of the batteries on my 24v setup I'll kill the batteries.  I also don't want to add a 4th battery to my small boat.  Can I run a parallel wiring setup to the 2 batteries I have while they are in series to the front?  My other thought was a way to reduce the voltage, but the load might be an issue.  I really don't need the thrust of a 24v transom mount, but if I have to go that route I will.  Anyone run a similar setup?

[delcecchi]

No you can't run the batteries simultaneously in series and parallel.  Best solution is to bite the bullet and go 24.

[marine_man]

Agreed... as you stated, if you're going to use the transom mount quite a bit, you risk running one of the two batteries down more than the other which isn't ideal.  24V is the cleanest option if you don't want to add another battery.

marine_man

[BobT]

One thing you might be able to do.  If you replace your starting battery with a dual purpose battery you could get some run time for your transom mounted motor but depending on the size of your outboard and how much you use the transom mount, this could run your starting battery down.  

I ran a Lund Rebel 16 with 40hp and a 40pd transom mount this way for years.  I could usually get quite a few hours on my electric before running the battery down to the point where it couldn't start my outboard.  This wasn't a concern for me since the outboard was easy to start with the pull rope if I needed to.