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Electric trolling motor setup, what do I need?

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    Posted: 31 Dec 2017 at 10:26pm
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I have been looking into an affordable electric trolling motor setup for my little 3.5 smartwave.

The option I am looking at is this 24lb Watersnake with a kayak bracket fitted. (https://www.marine-deals.co.nz/watersnake-asp-t24-sw-electric-trolling-boat-motor-with-kayak-bracket)

My thinking is this will allow me to operate from the front of the boat, either creeping up to surface schools without the motor noise making them disappear or quietly stalking the flats. I may even be able to slow my drifts with the lower of the two modes instead of using a drogue.

Notably this does not have all the benefits of the much more expensive minnkota setup, it is very manual and simple. Two speeds + forward and reverse with buttons. Steering is by an attached handle and stowing away is a few knobs. You can either remove it and stow away completely or lift and lay it flat alongside the hull (see video in link).

I can easily make something to steer while standing, would just have to bend down to switch speeds or stop/reverse. The steering can also be tightened or even locked fairly easily to maintain a set course.

My Questions:

  • Is 24lb thrust enough for a 3.5m plastic (smartwave 3500) boat with a 30hp 2 stroke motor?
  • How much battery power do these things use (can't find any info on their website).
  • Will I need a separate battery to avoid my main battery going flat or will my current (50Ah) be enough for a day's fishing?
  • How much water spray can these things handle, I can't find any reference to say how waterproof they are. It will get a tad wet some days while travelling if the wind gets up etc.
  • Is there any great flaws in my thinking?
  • Has anyone else had experience with using these, thoughts would be great.
Cheers,
Johan
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Post Options Post Options   Likes (0) Likes(0)   Quote FishMan Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jan 2018 at 6:07am
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Johan, I know very little about electric motors except that you will probably need an extra battery. Being reliant on one battery could lead to a certain amount of paranoia when using the electric Smile

And I would question whether you need an electric motor at all. Get rid of the oversized two stroke and replace with a smaller four stroke. Your life will change. I'm not sure what the 3.5m smartwave requires to get it up and moving, but surely a 15 horse four stroke would get it moving? Then you have all those quiet slow speed approaches at your finger tips. Four strokes absolutely purr at slow speeds and completely change how you approach a fish school.

Sure, four strokes don't have the same ultra-quiet boat positioning ability that electrics have in skinny water but you're fishing deepish harbour water where you're contending with surface chop and some sort of breeze on most days. In my opinion a four stroke is the better option.

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Post Options Post Options   Likes (0) Likes(0)   Quote Tagit Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jan 2018 at 8:05am
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Without getting into the specs of that specific electric motor etc you can do a few basic sums to get an idea of what sort of battery issues you might face.

A 50A/H battery @ 12v will give you a theoretical 0.6kw of power for one hour. Reality is less than this and if it is meant to start your main engine as well then you are probably looking at max 25% to 33% of that capacity. 0.6kw is around 0.8hp so your current battery might give you 15 to 20 mins of operating at less than 1hp. I doubt that is going to be enough for your needs?

Next thing is that very roughly 24lbs of thrust is around (depending on lots of variables) 0.3 hp (or less). That means that you could maybe operate that motor for around 1 hour and stay close to a battery level that will still start your main engine in a perfect world.

Bottom line is that I wouldn't run that off my main/only battery. I you dropped a single 8D (~200A/H) size battery into the boat for the trolling motor you get around 100A/H of usable energy without compromising the the life expectancy of the battery through over discharging. That might give you a normal day of usage doing what you are proposing. Also doubles as a spare battery for starting the main engine if ever needed. With a little simple cabling and a switch you could also have that battery get some charge from the main engine when it is running but with a small alternator on an engine like that probably not big runs between spots I doubt there is much value in doing that.

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Post Options Post Options   Likes (0) Likes(0)   Quote Snuffit. Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jan 2018 at 8:57am
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You will definitely need a separate battery, and a deep cycle battery at that. Deep cycles are designed to be drained to 20% of capacity on a regular basis, unlike starting batteries which will die if you treat them that way - which you will if you use your electric motor often. Your average sealed lead acid battery wont cut it either. Do some Youtube surfing and you'll pick up heaps of info. I run a Minn kota putting out 55lb of thrust of my 4.3m pontoon boat - you can pretty much cruise right up to normally spooky fish like trout without scaring them until they look up and have a WTF?!! moment :D so I definitely advocate them for ease of use and silent stalking.
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Post Options Post Options   Likes (1) Likes(1)   Quote Joker Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jan 2018 at 11:29am
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Be aware that the cheaper electric motors use a constant full rate of charge and tones it down with a rheostat for a slower speed setting. The Minn Kota at anchor lock uses a pulse mode of operation greatly increasing the useful charge.
At full bore on a 55lb motor with a 130AH deep cycle we get around than 1.5 hours before starting to degrade the battery life. At lower speeds 3/10 we get more than 6 hours. 

The 130AH 12v is a big battery weighing over 30kg

A better option might be towing a small sea anchor to slow you down on the main motor.

Here are some results that I got off the net for current draw from a Minn Kota 55Lb Terrova.
These results are pretty consistent with all other test results that I have seen.
Motor Speed......Current Draw (Amps)
1...................... 0.9
2...................... 1.5
3...................... 3.2
4...................... 5.2
5...................... 8.4
6......................12.7
7......................17.5
8......................23.5
9......................30.2
10....................36.5
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jan 2018 at 1:03pm
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Wow thanks for all the responses. Will have a good read tonight and post some more questions.
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jan 2018 at 10:51am
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Originally posted by FishMan FishMan wrote:

Johan, I know very little about electric motors except that you will probably need an extra battery. Being reliant on one battery could lead to a certain amount of paranoia when using the electric Smile

And I would question whether you need an electric motor at all. Get rid of the oversized two stroke and replace with a smaller four stroke. Your life will change. I'm not sure what the 3.5m smartwave requires to get it up and moving, but surely a 15 horse four stroke would get it moving? Then you have all those quiet slow speed approaches at your finger tips. Four strokes absolutely purr at slow speeds and completely change how you approach a fish school.

Sure, four strokes don't have the same ultra-quiet boat positioning ability that electrics have in skinny water but you're fishing deepish harbour water where you're contending with surface chop and some sort of breeze on most days. In my opinion a four stroke is the better option.


I like the idea but unless it is somehow nearly cost neutral I don't think it will be an option for me. I will investigate the cost though because the 15 or 20hp 4 strokes look like they have power trim and tilt, that would make me happy!

Till like the idea of maneuvering easily with the trolling motor though.
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jan 2018 at 10:57am
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Thanks for the info on the battery guys.  I will have a look at the cost of a 100Ah deep cycle battery.  From further reading that's what most seem to recommend for this motor and based on youtube reviews and such it looks like the 24lb will be enough thrust for my boat.

The big problem I have is where in the world I will put the battery.  It will have to be the centre console I suspect which will require a re-think of how I currently use the space but that is not a big deal. I am also considering a forward casting deck so it may be able to go under that.

I don't think I will bother with wiring to the alternator on my motor, but what about a solar panel instead? I have space on my centre console and have seen similar setups kayak guys use (battery box with solar panel on the lid).
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Post Options Post Options   Likes (0) Likes(0)   Quote Tagit Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jan 2018 at 11:26am
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The biggest solar panel you could probably reasonably fit (without having seen your boat) is probably going to supply maybe 8 amps in good sunlight. That would look like some sort of mini T-top in size. Reality might be a lot less than that if trying to just mount a panel on an existing smallish space. It would however probably extend your day a little and if parked exposed to the northern sun could be your off-water charger rather than having to plug in each time you get home (unless heading out again in the next couple of days). There are also flexible solar panels that can be used to fit odd shapes/spaces on the boat but that tends to get a bit expensive.

Extrapolating Jokers current numbers above for your motor it looks like you might be running around 10 - 20 amps in normal use or maybe a bit less even at times. That would suggest that a 100A/H battery would reasonably give you 3 to 5 hours of decent use before exceeding the 50% discharge level and starting to shorten the battery life. One better but slightly more expensive option would be to use a Lead Crystal battery which give almost 100% usable capacity without shortening their lifespan. That would give you maybe 80 - 90 usable A/H from virtually the same physical size battery.
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jan 2018 at 7:59pm
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Originally posted by Tagit Tagit wrote:

Extrapolating Jokers current numbers above for your motor it looks like you might be running around 10 - 20 amps in normal use...

That sounds about right. I found some limited info in a review that suggested it ran at 20 amps at the max setting. I don't imagine I would use it more than 3 to 5 hours in a day either.  Will look into the lead crystal and deep cycle battery options. Don't mind paying for decent stuff that lasts, just depends on how much it will be.

The other potential problem I found implies (but is not clear) that the head unit needs to stay dry.  Not sure if that refers to not dunking it or also no spray.  If it means no spray, well, then it is pretty much useless on my boat. It's a small center console and when it chops up things get wet and I have no space to stow the whole thing each time I move location.
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Post Options Post Options   Likes (0) Likes(0)   Quote Troutzilla Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jan 2018 at 8:19pm
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I'm not sure about the watersnake but we've regularly drenched our Minn Kota with spray ( and I mean drenched! )  and have had no issues.
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Post Options Post Options   Likes (0) Likes(0)   Quote JoshW Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 2018 at 4:56am
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Jofly, I agree normally you should probably have two batteries but since you have a 30hp 2 stroke, why not just the use existing single battery and pull start the 30hp if you need to.

Plenty of 30hp boats out there without electric start
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 03 Jan 2018 at 5:41am
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I like that idea. I do have pull start and have used it without problems before.

I already have a good battery location and it means I can add to existing wiring to do a clean connection for the motor.

If I upgrade the current 50Ah battery to something more beefy then I probably wont run into much trouble either as I only run a sounder and vhf electronics wise.
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Post Options Post Options   Likes (0) Likes(0)   Quote Snuffit. Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2018 at 10:19am
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... the addition of your casting deck gives you tons of space underneath for another battery Wink
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2018 at 11:58am
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Yes, it certainly does.  Had a brief test of the deck on the harbour last night for a couple of hours.  It was comfortable and stable. Even in a bit of chop I felt safe standing on it and casting the fly rod. Even managed a tidler snapper from the shallows despite drifting super fast in the wind.  Was nice to be higher up as well.  

Rather chuffed with myself even though it is a tad rough. Glad I don't have to chuck it all away. Not much of a DIY person Embarrassed

Will be easy to locate the battery underneath and the whole lot should be simple to remove when I want to go out in rougher weather.

Any recommendations for an affordable 100+ AH deep cycle battery?

I had a look at these https://www.marine-deals.co.nz/12v-100ah-agm-deep-cycle-battery

Only problem is it is 28kg!  That's a fair amount of extra weight in the bow, not sure how well that would go.

Know of any smaller ones or are they all that big and heavy?
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Post Options Post Options   Likes (0) Likes(0)   Quote Snuffit. Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2018 at 1:16pm
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I'm afraid they are big and heavy. Pig and I've never found a 'cheap' one. Confused
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 08 Jan 2018 at 1:45pm
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Thanks, that's what my research suggests. Will see ho it goes in the bow when I eventually get one, will just have to relocate it under the seat if it's no good.
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Post Options Post Options   Likes (0) Likes(0)   Quote Jofly Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2018 at 7:50pm
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Thanks for all the input guys, here is an update on the end result.

I located the battery under the casting deck in the bow and it fits well and the weight was not an issue during fishing yesterday.

The motor and kayak bracket is another story.  It was a total flop yesterday since the bracket is so high that the tip of the prop was too close to the water surface at the lowest setting, so the motor just created a big lot of froth and nothing went anywhere.

I had to modify two things to make it work and these are yet to be tested.

  • I lowered the bracket to it's minimum height, which involved chopping a stainless bolt and stainless tube from 80mm down to 20mm. So that will put the motor at least 60mm under the surface, which I hope will be enough.
  • The steering tension and locking mechanism was just weird, I don't know if it was just a factory glitch or operator error but it did not do anything unless I locked it in place.  I did just that (as a temporary measure) with epoxy to see if it will work. The epoxy won't last but on land tests suggests locking it in place will be the best final solution.
I also mounted the motor next to the center console. That removes it as a casting line tangling obstacle and with the adjustable steering handle allows me to steer from the front or rear.

Here are some photos of the setup.




Cut down bracket. The vertical metal tube was originally 80mm high, no 20mm.


Steering tention/locking mechanism as it was originally.


Now my temporary and very ugly fix locks it in place and I can use it to tension or lock the steering with the plastic wing nut attached to the other side of the bolt.  This will allow me to tighten it enough to make a longer steering arm which I can use while standing to adjust and set direction.  I will have to drop to my knees to change the speed or stop.  Best I can do with this setup.

Will let you know how it goes once tested.
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Post Options Post Options   Likes (0) Likes(0)   Quote WillP Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2018 at 9:21pm
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This thing is becoming a machine. well done.
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