I used to have a 12 volt MinnKota Riptide on my 18 foot Alumaweld Formula Vee and it did okay and the battery would last a long time....Never ever had it run out in one day, but I too had a perko switch hooked to two batteries.
I had the chance to sell my 12 volt and upgrade to a 24 volt and I am glad I did. It has much more thrust and it too does great in the battery dept. I do have the switch hooked up so I can Isolate my outboard's battery.
Get the most thrust you can afford, but remember the added weight of the batteries, which in my boat doesn't seem to make any difference. BTW the thrust on my 12 volt was 55 and the 24 volt is 74 I believe.
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C/R > A good thing > fish all day,into the night! Steve Ng

Dad, think that if I practice hard, they'll let me participate in the SRC ?
[Gig Harbor Puget Sound Anglers....Join your local chapter. CCA member