Trolling Motor Questions

[nokiddin]

Hey all. I am thinking about getting an electric trolling motor for my boat. Its an 18 ft starcraft holiday with a 90 hp inline 6 merc on the back.

I assume I need at least 55 lb thrust, and would prefer to stay with a 12V system. Since I have a closed bow with a fairly high front end, I think its best for me to stick with a transom mount motor.

My questions are, with a minn kota traxxis, or endura 55 lb thrust transom mount, how long of running time do you think I could expect? (of course I understand there can be a lot of variables, however, can anyone give me a general idea?)

Also, what is the best battery type? I'd prefer to not have to buy another battery charger, since I already have a conventional battery charger on the farm.

When I actually troll, would be pulling steel line for lake trout. The place I usually go has power restrictions for recharging, since it is remote and only has diesel generator and solar powered electricity, so I want to know how much an electric motor will restrict me, or if I should opt for a small kicker gas motor instead.

Thanks for your suggestions.

 

[Silvertip]

Re: Trolling Motor Questions

On that size boat a 55# motor will be operating at relatively high speed settings. The higher the setting the more current the motor draws. Exactly how much is simply not known unless you hook an ammeter (not a voltmeter) in the positive lead to monitor current draw at various speeds and wind conditions. But here are some numbers to chew on. A 55# motor draws 46 amps under worst case conditions but 1/2 speed is not necessarily 1/2 that value. But for purposes of this discussion lets assume you operate the motor at 1/2 speed for extended periods which is 23 amps/hour. As for battery type you need the largest deep cycle you have room for and your budget allows. Those batteries are rated by physical size (group 24, 27, 29 31 etc) and each group size has a RC (reserve capacity) number. A group 27 for example will have a RC number of 150 - 175 minutes at a 23 amp draw. What that means is the battery can deliver 23 amps for 150 - 175 minutes before it can no longer do so. So using those numbers, the battery would allow a run time of about 2.5 hours (175/60 = 2.5). Batteries are buckets of electricity so the bigger the bucket the longer the run time. The higher the draw the quicker the bucket empties. To carry this one step farther, if the motor operated continuously under worst case conditions the battery in the example would last only a little over an hour since it is drawing current at twice the rate the battery was spec'ed at (23 amps). Your home charger can either work fine for recharging or it can damage the battery. It all depends on how "smart" your portable charger is. Most old style chargers are not very smart and can ruin a battery if left on too long.

 

[sweet addiction]

Re: Trolling Motor Questions

I find this little chart very handy when selecting the right battery for the job.
Interstate Batteries

 

[nokiddin]

Re: Trolling Motor Questions

So, judging by silvertips example and sweet addictions chart, even if I buy the biggest battery I would get six and a half hours running time at half speed. If I understand correctly, with my boat I would probably be running at least half speed all the time, and with any smaller battery, it seems like I'd only get around 3 hours.

So for actual trolling, it seems a 55# TM with my setup probably isn't worth it for the amount of time I would get on the water, maybe only as a positioning motor I guess.

Would getting a 24V system, although more expensive, get me more time on the water? Or am I better off finding a small kicker gas motor for actual trolling?

 

[gm280]

Re: Trolling Motor Questions

I think one other issue Silvertip was trying to convey was that FACT that your trolling motor will have to work (and drain your battery(s)) so much faster trying to push your boat then pulling your boat. While it would seem the same effort to do it from either place on a boat, pushing a boat takes far more effort and attention to try and keep the boat going where you actually want to go. Mounting the trolling motor on the bow is such a better idea for a lot of reasons one being less drain on your equipment (battery(s) and trolling motor).

 

[Silvertip]

Re: Trolling Motor Questions

If you are really out doing serious fishing and trolling for six hours straight you need something other than a trolling motor. You didn't indicate just how fast you need to troll which is a giant factor in this application. But most folks will use a small 5 - 7.5 gas kicker for sessions that last that long.

 

[nokiddin]

Re: Trolling Motor Questions

With a bow mounted TM, would I get that much longer times? I don't necessarily go out for 6 hours at a time, but as I mentioned before, I go to a camp where they generate their own power with solar panels and diesel generators and it probably wouldn't be looked upon that nicely to be chargin up a battery very much, so if I go for a weekend or so and can't charge up, 6 hours fishin over the weekend is a cuttin' it a little short.

Seems a kicker would be best in this situation, however I love the idea of trolling in the peace and quiet of an electric TM. With the problem of me going to the camp ignored for now, would I run into any problems with a bow mounted TM on my boat? With the closed bow and it being quite high up from the water?

Thanks for your help guys, glad I didn't just go buy a 55# transom mount.

 

[Silvertip]

Re: Trolling Motor Questions

It doesn't matter if you fish 3 hours one day and 3 the next. That battery will not likely make it. You are in one of those situations where what you want to do requires compromise. You either use a small gas kicker, haul a portable generator with you (most have an 8 amp charging output), you charge the battery from your vehicle, take two batteries along, or you find a place to fish that has shore power. Don't even think about solar panels.

Bow mount vs stern mount will not likely gain enough run time to make the difference in price worth while. Since your boat is a closed bow, how do plan to get to it to deploy and retrieve the motor if mounted on the bow?

 

[nokiddin]

Re: Trolling Motor Questions

Seems the gas kicker is going to be best. Thanks for all the advice.

Is there a kicker plate out there that detaches fairly easily for times when you go on trip and don't need the little motor? Or is more of a bolt on and stay on kinda deal (unless you go through a fair amount of work)

 

[ondarvr]

Re: Trolling Motor Questions

We use 24V (i-pilot) bow mounted motors for trolling up to 7 or 8 hours at a time, but on multi day trips you either charge it back up at camp with a generator, or bring more batteries. This is for rather slow continuous trolling, but some of the boats are 20' or slightly larger. I also have a gas kicker.