Electric motor options for inflatable dinghy

[wyb2]

Originally Posted by zedpassway

...

Last summer I used the minkota 55lb thrust to get out to the mooring in about 1/2 foot seas, in my 10 foot Walker Bay dinghy and by the time I got to the mooring the 12 volt battery was down about 50%....

What was the battery? You can hook up anything from a 7 Ah powersports battery to a 200 Ah deep-cycle to a trolling motor.

[Steadman Uhlich]

Originally Posted by zedpassway

I have a 1003 model. Supposed to be about 2 hp. I also have a $200 Minkota.

My mooring is about 1/4 mile from the dock at the club. I keep the Torqeedo on the boat(its a 19 foot West Wight Potter micro cruiser) as a back up for the 6 HP Tohatsu. I don't use it for the dinghy, but I could. The dinghy has a 2.3 HP air cooled Honda OB because I need to leave it sitting at the dock all the time, and leaving a Torqeedo on the boat would cause it to be stolen. And the Honda does have more power to get it through swells to the mooring. The honda accelerates much faster than the Torqeedo, but they have the same top speed. It does make 5 times as much noise, since the Torqeedo is almost silent.

Last summer I used the minkota 55lb thrust to get out to the mooring in about 1/2 foot seas, in my 10 foot Walker Bay dinghy and by the time I got to the mooring the 12 volt battery was down about 50%. I had to run the Minkota flat out to move more than 1/2 a knot an hour. I used the Torqeedo to get the 19 foot sailboat back to the dock and then back out to the mooring again in 1 foot seas agains a 15 knot breeze, and used about 4% of the battery(pulling the dinghy too). I ran the Torqeedo at about 1/2 power and went 5 times faster. There is no comparison between the Minkota and the Torqeedo.

I actually removed the stern ladder and put in a new motor mount just for the Torqeedo in case i should need it. With two batteries, I can get about an hour at 4 knots, or 2.5 hours at 2.7 knots---on the 19 foot sailboat.

If you can afford the cost, The Torqeedo is head a shoulders above the competition, IMO. The competition's motors in the same category actually cost more than the Torqeedo.

I have three motors for my sailboat( the 6 hp Tohatsu, the 2.3 HP honda, and the 2.3 hp Torqeedo. Sailing(because we are all on a schedule) is 50% very slow motor-boating.

Good post. Thanks for taking the time to write your detailed report and comparison.

[GrowleyMonster]

A trolling motor can work if sticker shock keeps you away from the excellent torqueedo systems. You may want a prop change. Also cheaper trolling motors do not have a PWM power supply. Many have basically a resistor network for speed control, which is very inefficient except at full speed. But, PWM motor controllers are cheap as chips on eBay and you can connect one between your battery bank and your trolling motor, set the motor full power and leave it there, and use the PWM controller to adjust speed. This vastly increases range and efficiency. For a very portable power source, consider a 20AH 48v Lithium ebike battery. The controller should of course not be ran wide open with a 24v or 36v motor. Avoid 12v motors but if you just won't listen, at least test the motor for current at full power with a 12v battery and never use a power setting with the 48v bank that exceeds that. I like flooded cell lead acid batteries, except in the dink. Stuff happens, and often weight is an issue.

FWIW I ran my 7600lb 27' boat nearly 6 miles, at about a knot, a few months ago on an ebike battery. So pushing a dinghy at 3kts for a couple of miles should be easy sneezy, even with a trolling motor. Trolling motor, controller, and ebike battery would make a nice portable propulsion option. Remember even though the motor is down in the water where it won't easily overheat, and they are therefore very tolerant to overvolting, you CAN burn one up if you are really adept at destroying stuff.

[Peregrine1983]

Growlymonster and Zedpassway - thank you both... lots of great info here.

[zedpassway]

Originally Posted by wyb2

What was the battery? You can hook up anything from a 7 Ah powersports battery to a 200 Ah deep-cycle to a trolling motor.

250AH deep cycle battery. But the prop on a Minkota is nothing like the prop on a Torqeedo. Its runs fast and slices through the water. I had to run the Minkota at full power level 5 to get any forward motion at all. It might be ok for a small fishing boat in a quiet lake. Its almost worthless out on the water in near ocean in any kind of waves, in my experience.

[Martkimwat]

I use a powerful trolling motor on my Walker Bay 8 and I hook it up to a '36 hole' lithium golf cart battery which weighs about 1 Kilo. The trolling motor weighs about 6.5 Kilos so the whole lot only weighs 7.5 kilos. Nearly half the weight of the smallest petrol O/B. It will give me about 45 minutes at economical cruise (2.5 kts) or about 22 minutes at full power.(3.5 kts) and thats with a full load, I can row that fast when I'm on my own so only use it when I have company. (myself +2). The trolling motor is a 55lb pull model with a telescopic leg so it can be used as emergency power on my 27 footer too. It will push that along at about 1.5 kts in calm~ish water, enough to get me into my mooring after sailing as close as I can get.

[barnakiel]

Why a solar panel?

You need a battery anyway so skip this solar panel part and you are done.

b.

[wyb2]

Originally Posted by zedpassway

250AH deep cycle battery. But the prop on a Minkota is nothing like the prop on a Torqeedo. Its runs fast and slices through the water. I had to run the Minkota at full power level 5 to get any forward motion at all. It might be ok for a small fishing boat in a quiet lake. Its almost worthless out on the water in near ocean in any kind of waves, in my experience.

Wow, that's about a 150 lb battery. Must have been fun getting that in and out of the walker bay. Yes, according to everything I could find, the Minn Kota props are 4" pitch, vs 8.1" for the Torqeedo. So it would need to turn twice as fast for the same advance, all other factors being equal.

[PeterLIA]

The Torqeedo 1003 is perfect for a small RIB but won't plane unless you are one up. They have HEAPS of torque which is why they can use the BIG props versus the trolling motors. Also the 1003 has a new option of a bigger battery which nearly doubles the useful range.
Disclaimer - my business Broadwater Marine is the Philippine Distributor so maybe I'm a bit bias in thinking they are a great option despite the cost mainly because you don't have to worry about any fuel issues.
They also have an inbuilt GPS which is used to calculate and display range and time left so no guesswork required.

[44'cruisingcat]

[QUOTE=PeterLIA;2383679]The Torqeedo 1003 is perfect for a small RIB but won't plane unless you are one up. They have HEAPS of torque which is why they can use the BIG props versus the trolling motors..[c/QUOTE]


And 10:1 gearboxes?

[Adelie]

I have several suggestions.

For about the same price as the 55lb Endura you can get a 45lb Minnkota Riptide. Minn Kota® Riptide™ 45 36" V/T Transom - Mount Trolling Motor : Cabela's

While you will sacrifce about 20% of your thrust, you probably won't sacrifice more than 10% of your speed. Speed resistance curves work like that.

The Riptide is designed for saltwater so you can expect increased life from the motor. Also you won't be voiding the warranty by taking it into saltwater like you would with the Endura.

The 45lb motor only needs 12v so you don't need to load 2 batteries into the dinghy and you don't need to play electrician regularly.

Whatever motor you get you probably want to look at replacing the prop. The stock props on both Minnkota and MotorGuide are optimized for acceleration and weed shedding. You don't need those much, you want top speed and efficiency.
Kipawa props makes a range of props for about $35 or so that are so optimized. On the other hand using them voids your warranty for the motors.

Kipawa Propellers - High Performance 3 Blade Weedless Propellers

[mitiempo]

Originally Posted by Peregrine1983

Now I've been thinking about a cheap trolling motor and setting it up with a pair of 12v batteries in series and a small solar panel. Anyone have any thoughts?

Was thinking something like this, but with a shorter shaft... Minn Kota® Endura™ Max 55 Transom-Mount Trolling Motor : Cabela's

Thanks in advance

Make that parallel - the Minn Kota is 12 volts. They are only 24 volts if the thrust is more than 55 lbs.

[0urh]

Originally Posted by barnakiel

Why a solar panel?

You need a battery anyway so skip this solar panel part and you are done.

b.

To (re)charge the battery.

[mitiempo]

Like this

[Peregrine1983]

Hah. That's amazing.

A panel of that size would need a charge controller. With the small amount I use my dink and the short distances I travel on it I am nearly positive I'd be happy with a Minn Kota Riptide with a swapped prop, a cheap West Marine deep cycle battery, and a 6w Ganz solar panel keeping it topped off. I had great luck with the Ganz 6w on my old sailboat's start battery.

Adelie thanks for the advice about the prop.

Btw... Anyone want to buy a 2016 9.9 Tohatsu in great shape?