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Old 18-03-2022, 06:53   #1
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Advice on electric outboard for a tender / dinghy

So I just bought an Inmar 9-foot inflatable dinghy for my sailboat.

I imagine that the tender will be used primarily for short distance travel to and from my mooring, on day-sails and similarly to and from an anchorage on the occasional overnight sails.

I had thought that I would simply use a ~1hp 12v trolling motor for the tender.
Advantages - lightweight, easy to charge the battery
Disadvantages - low power, likely not able to plane the tender

I see that there are a lot of higher HP 48v outboards now available. Some of these are not much more expensive than the trolling motors. Even a small 3-4hp electric would have a performance advantage, but I am concerned that it would be more difficult to charge the battery, especially on board, since my boat has a 12v system.

Does anyone have any experience with these motors?
Thanks!
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Old 18-03-2022, 11:13   #2
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Re: Advice on electric outboard for a tender / dinghy

Even with a 4hp motor getting on a plane requires 1 crew on a very light RIB or folding dinghy.

I would count on being displacement only unless you actually have a RIB, and an Ultrlight to boot.

In displacement mode, the trolling motor is probably the best bang for the buck.
I’d get a MinnKota 45-55lb thrust with Digital Maximizer which increases motor efficiency.
I’d replace the stock prop with a Kipawa prop which will increase range about 15% at lower speeds or increase top speed a bit.
I would get a 60-80Ahr LiFePo battery from Amazon.
I would erect 2 vertical posts up 3’ from the transom and mount a 100W solar panel flat on top. Depending on how much motoring you do each day and how shady it is where it’s tied to the mothership that may be enough to keep the battery topped up.
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Old 18-03-2022, 11:56   #3
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Re: Advice on electric outboard for a tender / dinghy

If you need to plane, here’re the results of a survey I conducted here.

https://www.cruisersforum.com/forums...l#post3496301p
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Old 19-03-2022, 12:20   #4
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Re: Advice on electric outboard for a tender / dinghy

Here's a better link to the last update of the Survey
https://www.cruisersforum.com/forums...ml#post3516272
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Old 19-03-2022, 14:20   #5
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Re: Advice on electric outboard for a tender / dinghy

I use a Torqeedo 503 with extended battery life 915 Wh battery.
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Old 19-03-2022, 14:24   #6
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Re: Advice on electric outboard for a tender / dinghy

Quote:
Originally Posted by ramron67 View Post
So I just bought an Inmar 9-foot inflatable dinghy for my sailboat.

I imagine that the tender will be used primarily for short distance travel to and from my mooring, on day-sails and similarly to and from an anchorage on the occasional overnight sails.

I had thought that I would simply use a ~1hp 12v trolling motor for the tender.
Advantages - lightweight, easy to charge the battery
Disadvantages - low power, likely not able to plane the tender

I see that there are a lot of higher HP 48v outboards now available. Some of these are not much more expensive than the trolling motors. Even a small 3-4hp electric would have a performance advantage, but I am concerned that it would be more difficult to charge the battery, especially on board, since my boat has a 12v system.

Does anyone have any experience with these motors?
Thanks!
I have two electric motors, a 3 speed Newport trolling motor max 55 lb thrust with a 35 Ah battery. Go for back and forth to the mooring. At max power I do about 3 kts and draw 50 amps which gives me about 20 minutes at full speed on an 8 foot dink. It has a 40 watt solar panel so it is always charged when I go out. My cruising motor is a 3hp Torqpedo much more powerand much more expensive. It is computer controlled with gps, monitors usage tell time left and distance. At high speed fully loaded with 3 adults an a child on my inflatable it can drain the battery in 2 miles at max speed at lower speed much longer. On person much further maybe 4X. At lower speed up to 16 miles. I can change of 12 volt but take a long time. I have two batteries. The whole set up is about $3000. Most of the cost is the batteries. I went to this because I could no longer lift the 4hp Mercury of the dink, it weighed 45 lbs. The Torquedo weighs a total of 30 lbs and brakes down to two 15 lbs. half the battery, half the motor.

Hope this is helpful.
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Old 19-03-2022, 15:01   #7
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Re: Advice on electric outboard for a tender / dinghy

Quote:
Originally Posted by ramron67 View Post
So I just bought an Inmar 9-foot inflatable dinghy for my sailboat.

I imagine that the tender will be used primarily for short distance travel to and from my mooring, on day-sails and similarly to and from an anchorage on the occasional overnight sails.

I had thought that I would simply use a ~1hp 12v trolling motor for the tender.
Advantages - lightweight, easy to charge the battery
Disadvantages - low power, likely not able to plane the tender

I see that there are a lot of higher HP 48v outboards now available. Some of these are not much more expensive than the trolling motors. Even a small 3-4hp electric would have a performance advantage, but I am concerned that it would be more difficult to charge the battery, especially on board, since my boat has a 12v system.

Does anyone have any experience with these motors?
Thanks!
I think you have the right idea. Just watch the weather and currents since you won't be over powered. Keep a pair of oars.
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Old 19-03-2022, 15:28   #8
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Re: Advice on electric outboard for a tender / dinghy

Nestaway boats in the UK are supplier of both Torqeedo and Epropulsion electric outboards and can be very informative on the subject.

Their website is not well laid out, but I think it would be helpful to read throughly both their Torqeedo and Epropulsion pages. They are very long pages, with relevant information "hidden" by paragraphs of less relevant chuff; e.g. there is a "Power Comparison: Electric Vs Petrol" section on the Torqeedo page that I think is valuable, and which also applies to the Epropulsion outboards. They also compare previous models with current ones.

I'm not in the market for a new outboard, but I was quite impressed when I looked at them a couple of months ago - using the Spirit's regenerative charging on a Mini Transat looks amazing (video by "The Sailing Frenchman" on YouTube, Ep145). However I think planing may be a challenge due to the way torque is applied differently than by internal combustion engines.

I think both Torqeedo and Epropulsion can be charged off 12v using an adaptor.
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Old 19-03-2022, 15:34   #9
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Re: Advice on electric outboard for a tender / dinghy

Another disadvantage is having to carry a battery. It's hard to beat the energy density of gasoline. A gasoline outboard is also a spare motor. You can use the dinghy as a sort of "tug boat" for maneuvering or even propulsion in an emergency.
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Old 19-03-2022, 16:21   #10
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Re: Advice on electric outboard for a tender / dinghy

I once rigged a 1988 trolling motor to a kayak and it went 4.5 knots using 18 amps 12 volts. This motor was very old and not very efficient.

Inflatable dingys are not a very efficient thing to push through the water. It is surprising how many people use them when there are a variety of better alternatives. Consider a nesting sailing dingy. Consider kayaks (with sails/trolling motors etc) All of these will use a fraction of the energy to push under sail/oar or electric. They also are more easily repaired.
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Another disadvantage is having to carry a battery.
seems like less of a disadvantage than carrying gasoline. The battery can power other things like electric bicycle, or recharge the main battery if it's low. You can simply carry the battery in a backpack and plug it somewhere and recharge for free. Then if there isn't a lot of solar use it to top up the boat's battery bank.
Quote:
A gasoline outboard is also a spare motor.
So is an electric motor.
Quote:
You can use the dinghy as a sort of "tug boat" for maneuvering or even propulsion in an emergency.
This is may be possible but it is not a reasonable tactic. I can think of 3 completely different ways to maneuver and none of them involve propellers. Regardless, you can do this with electric just as well.

Filling the bilge full of gasoline and lighting it on fire is an emergency though. I saw a boat burn to the waterline because of this. Apparently they tried to fuel up using the rod holder. There is no telling where people will try to pour gasoline in your boat. I can only imagine this could have happened to me all the times I was offered free fuel, but fortunately I refused every time since I don't use fuel. Imagine the inconvenience of them pouring it in your water tank, trying to be friendly, but who is going to have to deal with the mess?
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Old 19-03-2022, 18:41   #11
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Re: Advice on electric outboard for a tender / dinghy

I've had a MinnKota 55lb thrust digital trolling motor (RipTide model for salt water) on my 9' rigid Puffin dinghy for 9 years. I have a 20w solar panel on the transom seat running thru a cheap ($10) charge controller to charge a GRP 27 deep cycle battery. I also replaced the battery after 7 yrs with.
The battery box is lashed to the center seat center support. The controller is in a tupperware container fastened under the little bit of "deck" at the bow. The only time I ran out of juice was when after 6 years the controller died.
It always starts, makes no noise & I don't have to worry about gasoline.
I was the first to go electric at the marina here in Belfast Maine & now there are 6 of us.
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Old 19-03-2022, 18:59   #12
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Re: Advice on electric outboard for a tender / dinghy

One thing I noticed is that full throttle is barely perceptably faster than 3/4 but uses way more juice.
I once got caught in a squall with 45k winds. I did use full throttle then & it got me the 1/2 mile to the boat.
Mostly I use it at 50% when having to row against wind & tide or if it's hot n humid & I'm tired.
If there is a con it's that when coming in to the dock with wind and/or tide running there's no steering so I added a detachable rudder - like magic!
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Old 19-03-2022, 19:45   #13
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Re: Advice on electric outboard for a tender / dinghy

Hull speed for a 10’ hard dinghy is about 4kt. And inflatable with a poor hull shape it’s going to be more like 3kt.
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Old 08-08-2023, 09:36   #14
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Re: Advice on electric outboard for a tender / dinghy

Congrats on the new Inmar dinghy! Considering your usage, I'd suggest taking a closer look at the PARSUN JOY 1.2 Electric Outboard Motor – it might just tick the boxes you're thinking about.

You're spot on about the 1hp trolling motor being lightweight and easy to charge. But yeah, it might not give you the oomph to get your dinghy on plane. Now, those 48v outboards are tempting, no doubt. Yet, I get your concern about fitting it into your 12v system – who needs extra complexity?

That's where the PARSUN JOY 1.2 could shine. It's got a bit more punch than a 1hp motor, so you could have some fun planing. The cool part? It's made for a 12v setup, just like your sailboat. Charging it should be a breeze, and you won't have to do any fancy wiring gymnastics.

Take a quick look at user reviews and experiences to get the lowdown on how it performs day-to-day. It might strike that sweet spot between power and practicality, making your dinghy trips even more awesome.
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Old 08-08-2023, 12:38   #15
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Re: Advice on electric outboard for a tender / dinghy

The dinghy isn’t new anymore. This thread started 17mo ago.
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