Solar Trolling motor on a Dorry? Bad idea?

[onesea]

Ok I have read a bit but the idea but it keeps coming back.

We use a 11’ dorry as a tender (300kgs) always kept afloat and the bottom is not always the cleanest.
Presently we use a 2.2hp 2 stroke which is fine rarely gets above 3/4 throttle even when dinghy is weedy, there is 4 knot speed limit.

Distances is about 0.5 miles to the boat and the same back currents maybe 0.5 knots at worst.

Dinghy would be used at most a couple of times a day for 3 or 4 days then left to recharge on solar for 5.

Dinghy is used all year in flat water with 2 people and 2 dogs and gear (300kgs total max), in most winds (I often go out and get on with maintenance when weather unfit for sailing). Presently I will not leave the outboard on the dinghy for theft reasons, so we carry it to and from the dinghy a few 100m.

Torquido type engines are same weigh as 2 stroke so of little benefit for much ££££

However I have been pondering replacing with a trolling motor (10kg - £200?). Leaving batteries (free) in dinghy to charge from solar panels (£100) on an arch on the dinghy.

At that price I could even consider leaving outboard on dinghy and just making it inoperable.

Would a trolling motor be up to job? What size trolling motor/ solar/ batteries would you recommend?
Any other affordable suggestions?

I am thinking 100w Solar
If anyone has trolling motor in Solent region to try I would be interested.

 

[Dellquay13]

IIRC, not many of the trolling motors survive long in saltwater, despite claiming they do

 

[jaminb]

I had a Drascombe Longboat on the Thames (non salt water) and did exactly as you are proposing. I went for 24v trolling motor and two leisure batteries. I have a couple of the folding flexible panels (a1 size when folded) and charged fine over a week from may to Octobe.

set up worked perfectly for me but wouldnt fancy it with strong tide, winds or waves.

 

[Kelpie]

Just to give a data point, my 68lb trolling motor can move my very light 11ft dinghy at about 4.5kt.
It works reasonably well but despite being rated for saltwater use, it has pretty much fallen apart. It still works but things like the shaft clamp no longer work.

 

[rogerthebodger]

https://flic.kr/p/WVjhbh

Solar powered run about used in my old marina

 

[Minerva]

Just to give a data point, my 68lb trolling motor can move my very light 11ft dinghy at about 4.5kt.
It works reasonably well but despite being rated for saltwater use, it has pretty much fallen apart. It still works but things like the shaft clamp no longer work.

What brand of motor do you have?

 

[Grith]

Our torqeedo propels our 28 foot trailerable cruising yacht ( yes yacht despite the monster secondary motivation equipment) in no/low wind situations then unships and becomes our inflatable dingy outboard which it can push to 4 knots. Seen here connected to our solar system charging whilst underway and in use.

 

[Tranona]

As with most things, you get what you pay for. Trolling motors were designed for different patterns of use than moving heavy dinghies. Their advantages are lower cost, lighter weight and no petrol. Downsides are limited power, separate battery requirement (which might also mean limited range) and lack of robustness, even the so called seawater ones.

However many can live with these limitations and your usage puts them in the frame. The reservations would be lack of power for the heavy dinghy (and load), although a 55lb and upward has thrust comparable with a 2hp outboard, but at maximum power and therefore shortest range.

Probably worth a punt, but if you have a good working outboard why bother? If you do, leaving the batteries in the boat with solar is a good idea, but don't leave the motor out in the elements!

 

[LiftyK]

If you’d like some inspiration take a look at the “rctestflight” channel on YouTube. Don’t be put off by the name. His most recent project was posted just eight days ago. It is an episode “building an unlimited range electric boat”, using solar power on a small boat. The guy is a smart young engineer and he explains everything clearly.

 

[Kelpie]

What brand of motor do you have?

It's a Bison.
In fairness I haven't treated it very well, it spent a Scottish winter on the back of a dinghy on an exposed pontoon.
It's just a shame that they didn't use stainless springs, nuts, and bolts. In retrospect it would have been wise to have swapped them out at he start.

Another flaw for regular use is that unless you devise a solution, the standard method of connecting the power leads to the battery leaves everything exposed and inevitably saltwater will do its thing. It wicks through the copper strands and you have to keep chopping a few inches off the cables and putting new crimps on.

 

[Neeves]

It's a Bison.
In fairness I haven't treated it very well, it spent a Scottish winter on the back of a dinghy on an exposed pontoon.
It's just a shame that they didn't use stainless springs, nuts, and bolts. In retrospect it would have been wise to have swapped them out at he start.

Another flaw for regular use is that unless you devise a solution, the standard method of connecting the power leads to the battery leaves everything exposed and inevitably saltwater will do its thing. It wicks through the copper strands and you have to keep chopping a few inches off the cables and putting new crimps on.

'One' expects an outboard to be somewhat resistant to the elements - you really should not need to replace everything as you take it out of the box (and tinned cable would help). In terms of an OB, electric or not, stainless bolts are not a big financial issue (though stainless into an aluminium casting might be, an issue)

I sympathise with you

Its all a bit disappointing

Jonathan

 

[rogerthebodger]

I an about to fit my trolling motor to my dingy with a Lifepo4 battery and a small solar pane to keep the battery topped up. Just waiting for the battery to arrive

 

[Tranona]

'One' expects an outboard to be somewhat resistant to the elements - you really should not need to replace everything as you take it out of the box (and tinned cable would help). In terms of an OB, electric or not, stainless bolts are not a big financial issue (though stainless into an aluminium casting might be, an issue)

I sympathise with you

Its all a bit disappointing

Jonathan

Just reflects the fact that these motors are not "serious" for general saltwater use, whereas a Torqeedo or e Propulsion are - at 3 times the price.

They have their place in the market if your pattern of usage fits with their limitations.

 

[B27]

I was in the Yealm a few weeks ago, it seemed to me my 'Ancient Mariner' was unreasonably noisy at 7AM.

I don't see myself coughing up two grand for a Torqeedo, but a couple of hundred for an electric outboard could be a temptation.

Petrol outboards are also grubby smelly things which you don't rerally want in a nice car.

I've seen a few people using trolling motors on powerboats for fishing, had a chat with one owner who said he'd had his for a couple of years no problems, just rinse it and give the metal bits a sniff of WD40.

 

[B27]

Just reflects the fact that these motors are not "serious" for general saltwater use, whereas a Torqeedo or e Propulsion are - at 3 times the price.

They have their place in the market if your pattern of usage fits with their limitations.

3 times?
I thought these shiny options were well into 4 figures, whereas an ebay trolling motor is £130 plus battery?

 

[rogerthebodger]

If you get a leg from an old petrol outboard and fix an electric drill onto the top of the drive shaft you can get a very cheep electric outboard

 

[Kelpie]

I paid £100 for my Bison secondhand, in as new condition. Then added a 60Ah lithium battery for £280. That battery has now become a useful extra to my main house battery, which has saved me a few times now.
Of course I could have spent £50 on a small car battery instead.

Torqueedo/Epropulsion seem to start at about £1500? So it's a very different proposition.

In defence of the bison, it is lovely to use. Always starts first pull. Almost silent. F/n/r which small outboard don't have. My wife and son both like it, it's much less daunting to use than a petrol engine. And with a 60Ah battery I have 1hr range which is slightly more than I get from a tank of fuel in my 3.5hp 2 stroke.

Maybe I will put it back in to use one day. I would want to find a suitable pelican case or waterproof toolbox to put the battery in, along with Anderson power connectors, and a battery monitor. The unbranded ones are under £50. So total extra cost not outrageous.

By the way, it's not hard to shorten the shaft on these motors- just unbolt the head and saw a bit off the tube, being careful not to damage the cables.

 

[Minerva]

One minor thing that's always bee a bit of nuisance - the last thing off the tender is the outboard and petrol tank, yet this needs to be the first thing in the boot of the car so we end up with all our bags strewn around the car at the end of the sail. The ability to just throw an electric trolling motor in last without fear of petrol / oil going all over our bags would be appreciated.

I've noticed decathlon sell a bison electric outboard - I know from experience they have very good customer service around refunds / replacements of faulty goods.

£200 for the motor, £400 for a 100ah LiPo4 battery, £200 for an extra 100w PV panel on the boat with MPPT charger and a £150 mains battery charger at home leaves £50 out of a grand to buy a waterproof box for the battery - the whole package with a decent motoring range would come in at a grand. Probably even cheaper if you already have enough solar installed on board.

 

[B27]

It's like electric cars I suppose.

What range do we need?

I'm thinking most ports I go into it's 5 minutes from mooring to pontoon?
If we anchor, it's normally similar.

There is the odd place like Salcombe where it can be a long slog to windward to get to town.

Recharging from the boat's solar on a grey week's cruise when you want to go ashore a lot could become limiting.

 

[onesea]

The way I am thinking the batteries will lead acid (probably from a marina skip at end of season 100amp hour?) in standard battery box’s. I will not be taking them out of the dinghy routinely. They help the dorry self drain on the mooring and would replace my present ballast. Lithium batteries would be to expensive to leave in the dinghy they would get borrowed.
The tender stays in the river and Initially I would not replace 2stroke outboard for inflatable tender.

@LiftyK the set up I am think about is similar to rc’s but with battery to power the runs to and from the boat and solar to charge the batteries.

Connection wise I would put decent waterproof connections on the outboard and battery connection.

I guess the question is how many lb thrust motor 68lb (12v) or more? 24v 100lb?