Battery boat- how many to avoid being stranded??

Okay guys...
I'm planning on purchasing an 18ft Alumacraft weighing in at 690lbs (MV1860AW). I would like this boat to be electric powered only (gas not allowed). The boat will be meant for slow cruising speeds, mainly circling the lake with occasional anchoring stops. I would like it capable of powering with up to 4 individuals. My question is, how many batteries would you guys recommend to run this setup given the weight range? The average speed would rarely exceed 3mph but I'm usually out there as long as 7 hours at a time (tops). I'm expecting to purchase AGM optima batteries but have no experience with them (and have no idea of how many I'd need to run a setup like this safely.) I'll buy what's ever recommended.

Also, what kind of trolling motor would you recommend for this? Even though it will be meant to cruise, I do want one of the most powerful motors just to know it's available when needed.

Re: Battery boat- how many to avoid being stranded??

You gave us absolutely no useful data. 1) How big is the body of water? 2) How many miles do you plan to cover in 7 hours? 3) What other electrical accessories are on this vessel? 4) what size motor do you plan to use for propulsion? See where this is going??? Batteries don't have an unlimited capacity and electric motors use lots of current. As an example, a 55# thrust trolling motor draws about 46 amps at full speed (which by the way is about 2.5 - 3 mph). For your purposes you will need a 24 volt motor which puts you up into the 80# class minimum for the load you are carrying. That means you need a minimum of two large deep cycles (group size 27) wired in series. How long that would push the boat depends primarily on the current draw of the motor. That's why we need to know what your plans are for power.

Re: Battery boat- how many to avoid being stranded??

Are you thinking electric because the lake requires it/personnal preference?
To get 3-4mph almost any trolling motor will be wide open(there not built for speed).Running a trolling motor wide open for along time at wide open isn't good for them plus like mentioned earlier with the amp draw,may not get your 7 hours.
If it's legal,a small 4 stroke(2-4hp)is quiet and pretty easy on gas.I'd say more efficeint at trolling for longer periods,steady.

Re: Battery boat- how many to avoid being stranded??

Sorry about leaving some important facts out. The lake itself is a 1,450-acre body of water. I really don't plan on going out too far. My guess would be that my actual distance of travel would be no more than 4-5 miles in a LONG day. And by that distance, I mostly am talking about circling near the dock, not traveling more than a 2/3 of a mile away from it. From you guy's response, I'm thinking I may have depicted an unrealistic speed of 3mph. It's hard to tell since I'm only referring from perspective rather than a speedometer reading. I just got on my treadmill and it seems like 1mph is more accurate of what I'm shooting for as far as (average) thrust speed is concerned. As far as other electronics on the boat: a transom mounted 360* light, and bow mounted red/green light (for night use.) I am most likely going to look into a fish finder although it's probably not even necessary. As far as the motor power, that's actually what I'm wondering from you guys. I've been used to my 30lb endura on my 9ft pvc inflatable seahawk, so this is a whole new territory for me and will be my first solid structure boat.

Pootnic- The main reason for the all electric setup was for efficiency reasons as well as keeping my gross weight near my vehicle's tow capacity (and since my required speed is very slow). You do have a good point however and I will see what the low hp line of gas motors has in terms of price/weight/efficiency. If the numbers match up, it might make sense to consider one along with the electric and then delete the need for a few extra batteries.

Re: Battery boat- how many to avoid being stranded??

For the best effiency you are going to need a digital trolling motor, something like a MinnKota Traxxis 80# thrust That will set you back around $600. Then a couple batteries would be anywhere from $200-400 depending on how good of batteries you buy. But, this is just a trolling motor and max speed won't be fast.

Torquedo is an electric outboard that will have better speed, but it's not cheap, $1700 on up.

I have a 70# digital MinnKota transom mount that I run on my 2000# 18' Crestliner. It's not a speed demon, but will go a long time on 2 group 29 batteries. I run it at 1/2 speed or less while trolling. Wished I had the 80# model though...

Re: Battery boat- how many to avoid being stranded??

As you can see, electric power as the primary source of propulsion for boats is still a fair distance off although perhaps a hybrid of some type may appear in the near future. If there is no restriction -regarding gas engines and speed is not a factor, then any of the small 4-stroke gas outboards makes much more sense. If you are on a restricted lake, then electric is your only choice and that takes a bunch of battery power. A small outboard would easily exceed 3 mph and allow you to get off the lake much quicker in an emergency (bad weather for example) than the electric. Time to re-think??