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PostPosted: Tue Apr 03, 2018 10:45 am 
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Location: Cheshire, CT USA
So I finally bit the bullet and bought a Minnkota 55lbs thrust saltwater transom mount motor and 35Ah AGM battery. Just got delivered to my house last weekend. Motor is ultra quiet as tested in my garage. I know it's not as powerful as my old 2hp Honda but the quietness made it seem even less powerful than expected. Planning a test run later this month on a lake. As I am in CT, it's still in the 40's and ice cold water so I'm planning to run the motor in a barrel of water in my garage to get an idea of battery life at various speeds. 30 day return policy so I do want to get on the lake without rigging just to see how fast it can move the boat. If I am satisfied with speed, I plan to run extension wire through the hull from the storage cooler (35Ah battery is only 7 x 5 x 6.5 inches) so it fits in the hull cooler) with quick connects at the motor and battery. Then if battery life isn't more than 1 hr, I may buy a second battery to keep in the opposite hull as a back up and to help balance the boat. Motor supposedly draws 50 amps at full throttle so that's just over half an hour of battery life at full speed theoretically. No data on amp draw at 50 or 75% throttle. So far though, geometry of the motor head and center of gravity (all the weight is in the prop end) is a little different than my 2hp Honda and the tiller does not fold back like the Honda so mounting on my transom mount might need some tweeking. I will post some pictures once I have things worked out.

Keith

First thing I thought of when I saw it was the droids from Star Wars Clone Wars. :lol:

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PostPosted: Tue Apr 03, 2018 11:26 am 
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Location: Benicia, CA
Assuming you get to like the motor, next season after the AGM battery is needing replacement (or for a spare), spend the extra cash and get a Lithium Ion battery. It is 1/3 the weight, holds charge without draining when not in use (so don't need to keep it on a battery tender) and packs more amp-hours for longer use. "Probably" could even boost voltage and motor power (electric bicycle guys do it all the time with their hub motors) but I'd wait until sure you need it. Sure, it costs more initially, but you get 2000 charge-discharge cycles from lithium and only a couple hundred from AGM. Just sayin'... I replaced my BMW motorcycle battery with lithium and am in my third year on the OEM lithium battery on my electric bike...you can say I'm a believer (like all the Prius owners out there).

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PostPosted: Wed Apr 04, 2018 4:58 pm 
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Hi guys, check out my electric motor and mount on my Hobie Getaway. It is 32lb thrust lithium ion Shakespear motor so it works well with a few people on board. Goes even faster with the rudders lifted so there is less drag. Battery plugs into the head of the motor. Here is the link to the forum where there are pictures (scroll down a bit):

https://www.hobie.com/forums/viewtopic. ... 1&start=60


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PostPosted: Tue Apr 10, 2018 10:57 am 
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Location: Cheshire, CT USA
I finally got a chance to test the Minnkota 55lb thrust trolling motor with a 32Ah AGM battery. Ran it in a 35 gallon drum of water for 2 hrs on 50% power. It was still running but the battery indicator showed that it was drained so I stopped the test. Didn't want to damage the battery by running it too low. Put the battery back on the charger and it was all charged in the morning. I will run another test at 75% and 100% power soon. I only have amperage draw numbers from Minnkota of "max 50 amps" so I'm guessing:

50% throttle = 2 hrs run time which should be about 16 amps
75% throttle= TBD (guessing about 60 minutes at 32 amps)
100% throttle = roughly 38 minutes run time at 50 amps (based on minnkota manual)

Of course I have no experience with batteries and have read that AGM's should not be run down below 50% so that seems like a waste of potential energy. Not sure the logic behind it but at least I now know that I can run it down if needed. I'm guessing it just shortens the lifespan of the battery. I don't mind buying a new one every couple years if needed. It's way cheaper than the cost of tune up of a 4 stroke and carb rebuild every year.

Also, I expect the amp draw and run time will probably be different when under load of pushing a boat but I'm just looking for a baseline for now.

Keith

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PostPosted: Tue Apr 10, 2018 1:05 pm 
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KeithB wrote:

Of course I have no experience with batteries and have read that AGM's should not be run down below 50% so that seems like a waste of potential energy. Not sure the logic behind it but at least I now know that I can run it down if needed.

Keith


Pretty much all battery testers are only measuring voltage at the terminals. So the "power meter" is simply telling you what the battery voltage is. And a fully discharged battery is typically only a couple volts down from the stated voltage and fully charged is typically slightly above the stated voltage. When they tell you not to discharge below 50% they are trying to help you optimize the number of charge/discharge cycles your battery will sustain before replacement. Even more important, though, is that an electric motor running at a lower voltage uses many more amps to get the same power. P=V*I where P is power, V is Volts and I is current (amps). If there is insufficient heat sink (probably not a problem with an immersed motor) the windings can overheat.

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PostPosted: Mon Apr 16, 2018 6:53 am 
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Location: Cheshire, CT USA
I was able to get the boat out on a small local lake to test out the Minnkota 55 on Friday. No mast or sails, just the boat with rudders and motor and my 9 year old son and I. It moves the boat but much slower than the gas powered 2hp Honda. Or maybe it just seemed slower due to the quiet because I was able to record about 4mph at full throttle against a 10mph wind using a speedometer app on my phone. Downwind was about the same. I guess I never recorded speed with the Honda. If that was 4mph, I'm guessing I was seeing at least 6-7mph out of the Honda. Anyway, no significant decrease of speed at 75% throttle. Reverse gear didn't do much to move the boat. The prop turned but the boat barely moved in reverse. So we tooled around the lake for about 30 minutes at 75% throttle and called it a day. Battery had about 50% charge left when we stopped.

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PostPosted: Fri May 18, 2018 9:08 am 
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Have you had any more experience with the 55? I am thinking about a similar motor. I have a 3.5 hp 4 cycle and I am a little afraid of the amount of weight...
It sounds like it was driving you OK against a headwind, would like to hear more if/when you sail with it...


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PostPosted: Fri May 18, 2018 10:33 am 
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Quote:
It sounds like it was driving you OK against a headwind...


Yes, but that we with no mast or sails, so not much windage. And just one adult, one kid.


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PostPosted: Fri May 18, 2018 1:53 pm 
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interested to hear how it works once you get to really sail with it


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PostPosted: Mon May 21, 2018 4:14 am 
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I was hoping maybe Memorial Day weekend but weather may not cooperate.

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PostPosted: Mon May 21, 2018 5:13 am 
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excellent, if we are lucky up here in NH may be able to get my "new" 2005 into the (lake) water about that time too, we'll see.


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PostPosted: Mon May 21, 2018 6:18 am 
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Location: South Boardman, Mi
I ran a 50lb thrust motor on my 21SC, but later switched to a 2hp 2 stroke.

50lb electric observations:
+Quiet
+Lighter Motor
+Longer, adjustable shaft
-Required charged batteries
-Limited Range
-Much less power
~3mph

I had a 35AH deep cycle AGM battery, 12V. For motoring under 1/4 mile it worked great. Anything longer and it was a bit of a disappointment. The motor had enough power, but with a 35AH battery it lacked the range.

Wire gauge is another concern. With a 12v 55lb thrust motor you will likely need to run 8 gauge wire, or keep your wire lengths short.

Gas Motor observations:
-loud
-shaft too short
-heavier
-drank gas
-leaked gas in certain positions
+way faster than needed
+extended range
~6mph

Personally, if you just need a little kicker around the docks, a 30lb electric will do fine, and a 50lb will give you extra power for short bursts of speed. 35AH is probably about right for your needs. The real benefit of going electric will be felt when you add a marine stereo system to your boat with a couple of 80W speakers


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PostPosted: Mon May 21, 2018 6:31 am 
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yeah, always a trade off, where is that free lunch (I'm hungry)...

On my gas motor BTW I switched to only using the very expensive no ethanol gas in a can, like from home depot. Carb has been happier so far...


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PostPosted: Mon Jun 18, 2018 1:53 pm 
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Yeah, I've been using Tru-Fuel (ethanol free) for several years but still always had carb issues.

Anyway, finally got out on the water on Saturday. Still cool on the water but a light jacket made for a great day of sailing. 10-15mph SSW wind was perfect. Furled the jib out in open water and let the main luff while trying out the motor in light chop and head wind. Basically no forward movement or very little. Not impressed at all. Used the motor when coming back to the launch as someone heading out had tied off right at the end of the dock and I needed to get around them dead into the wind. Can't really tack my way forward in between the launch docks. Motor worked fine, albeit slowly, to get me in the last 100 yards.

Wish I could rig up an impeller system like a wave runner inside the hulls. That would be sweet instead of this ridiculous looking trolling motor dangling off the stern.

Edit: forgot to take any pictures. I'll be out again next weekend and will be sure to take and post pictures.

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PostPosted: Mon Jun 18, 2018 2:02 pm 
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thanks for the update Keith, sounds like no good into the wind. But I guess the most common use case is going to be no wind...so maybe still some hope.


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