What size battery for a 38lb thrust motor?

I want to mount an old minn kota endura 38lb thrust motor to my pa14 but I know next to nothing about batteries. I know I'll need a deep cycle one but that's about it. What size battery should I get to power this motor? Ideally I would like to get at least 4-5+ hours of use at the top speed setting.

From what I could locate on line, it appears your 38 lb thrust motor, at max speed will draw around 40 amps at 12 volts......so that's basically 40 amps per hour.
If you have a 12 volt deep cycle battery, rated for 100 amp hours (Ah) and you run the motor at full speed (40 Ah), the fully charged battery will be depleted in: 100 Ah / 40 Ah = 2.5 hours.....that's it.

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Dr.SteelheadCatcher
Warrenton, OR

And you'll find that it greatly slows long before that amount of time is up.

One of the reasons for selecting smaller motors is that they'll push your boat just as fast as a larger motor (or nearly so) and do it for a longer period of time. Of course, if that's what you've got, then that's what you've got.

Ok, that makes since on the amps. I'm not 100% committed to this trolling motor, I picked it up on Craigslist for $40 or $50 a while back. I'll see how it does, keeping an eye out for a smaller motor though. Thanks

Keep in my mind dropping down to 30 or even 28 lb motor won't change the current draw that much.
I would determine the max weight you want to add in battery size and where to store it. I think you will find you won't use top speed #5 very often.
If you could come across a digital maximizer TM circuit that might help the efficiency.

We use 22-NF 55Ahr AGM's mounted inside the center hatch and slid back between the scupper tubes, it's a perfect fit. With a PWM throttle control you can get around 4 hours cruising time, remove the tackle tray and add a second battery to bump your run time to around 6 hours. A 30 thrust is good in calm fresh water but I use a 45 in salt to a give me the speed to keep the bow up when swells or strong currents are coming for behind, which causes the bow to dip and wanting to rollover.
A group 24 79Ahr AGM will fit inside the center hatch if it's laid on it's side.
Tom has a point, the smaller motors 30-45 have a smaller footprint and have less drag than the larger 50,55's
at time the smaller motor is faster because of this. However the torque of the larger motor won't be there.
Another thing to look at is the prop, the stock 2 bladed props tend to "slip" while trying to push a heavy boat, at times you can back off the throttle and you'll pick up speed as the prop grabs, if possible try to run a 3 bladed prop like our speed prop, which is a Motoguide prop modified to fit a Minn-Kota.
http://bassyaks.com/photos/img_20120725_200032/

tight lines
Steve
Bassyaks.com