Electric outboard for a spindrift?

[Aphers]

19 hours ago, Captain Tim said:

After seeing what goes on inside one of those lithium batteries, I'm happy I went the 2.5 hp Suzuki route.

29lbs plus 8lbs for extra gallon of gas. As a side note, I buy my gas at the local airport which is ethanol free. I think this is a huge reason the little Suzuki starts and run so well. 

 

The good quality batteries are safer than carrying petrol around. 

But the cheap knock offs are potentially very dangerous. 

If going the electric route, you need to know what you're doing. Correct cable sizes, good quality connections, and appropriate fuses are essential. 

 

There are many stories about fires caused by lithium batteries. In every single case these are poorly built or installed, and almost always a volatile chemistry like LiPo or NMC, rather than the much safer LiFePO4.

[paul_stewart]

"LiFePO4  cells are incombustible, which is an important feature in the event of mishandling during charging or discharging. They can also withstand freezing cold, scorching heat, and rough terrain. When subjected to hazardous events such as collision or short-circuiting, they won’t explode or catch fire.  Also,  LiFePO4 batteries are non-toxic, non-contaminating and contain no rare earth metals and no cobalt or nickel, making them an environmentally friendly choice."  -- relionbattery.com

 

Regarding the meaning of "incombustible",  it's reasonable to follow the advice of Will Prowse.

He says a LiFePO4 battery is like metal box full of wood.  It's stable and is not going to spontaneously combust or explode.  Of course, if the entire boat is already a bonfire, then you could make it burn. 

 

Caveat emptor:  when purchased from a reputable dealer.    

[Bryan Rolfe]

Any time you store energy in a confined space, be it gas, diesel, or various battery chemistries, and design that stored energy to be "easy" to release, there's a risk of that energy releasing much faster than you intended. Gas is probably the most dangerous, followed by LFP maybe, and then diesel. Usually the bigger risks with any battery system is the wiring not being properly protected, and a short causing a fire that way. 

Off topic: Will Prowse has really good when he sticks to the subject matter he knows well: batteries and solar. However, he has in recent years chosen to share some of his pseudoscientific views, particularly about drinking alkaline water and chemicals in our clothing causing health issues (which is why he is always wearing a merino wool shirt in his video). Neither of which are supported evidence-based research.

I just find it interesting how people can use data-driven analysis rigorously in one aspect of their life, and would probably poo-poo anyone making claims about batteries that are not supported by data, but are willing/able to completely ignore it in other aspects of their life -- or more likely, they just don't trust it if they didn't do the testing themselves. 

[Don Silsbe]

I’ve been around gasoline-powered engines for 70 of my 76 years.  We played with them on a daily basis, when I was a boy.  I’ve never experienced one fire.  If money were no object, and I could afford the extra batteries to extend my range, I’d probably join the crowd.  But for me, my little Suzuki is a thrifty, trouble-free auxiliary.  

[Steve W]

I have a Suzuki 2.5 I love. Plenty of power. Unlimited range.

And hate. Loud with no reverse.  I am going electric some day.

 

 

[Lille Ø]

Today we picked up a new ePropulsion Spirit 1.0 Plus here in Grenada. At 1kW, it is more powerful than what our Spindrift 9N needs. On that level, the smaller eLite would be a better choice. But we bought the bigger outboard for the bigger battery capacity. Initial test runs in flat water say that at around 120W power we move at 3kt, and BMS estimates range to be 8.5h, so around 25NM.

 

As a bonus, with some additional parts (a cable and a DC-DC converter), we will be able to use the ePropulsion battery as an emergency battery also for the big boat.

[Oyster]

Quote

when purchased from a reputable dealer.   

Being in the rv side of off the grid and self contained setups, lithiums  are widely used and comes with a wider  range of quality and results. This gets discussed all the time.  The issue when buying lithium batteries is that local battery outlets are pretty selective in wanting to sell them.  Purchasing from Amazon comes with a risk, mainly service and quality. The huge selling point is that "you can get ten years of service from them" I say if there was any ifs, ans and butts to that story, then you can attach that to lithium batteries, dependent on their owners a larger percentage of the time.

 

Battle Born batteries offers a bit better quality and service. Of course that comes at a higher price than the constant quality issues, but much cheaper with the Chinese built lithium batteries that pops up overnight on the web for sale.  The quality is all over the place. Of course on the opposite side of the conversation pertains to the owner. Proper charging does require a dedicated battery charger. Of course a regular charger will bring them up to snuff enough to use them. 

 

But for the sake of this topic here dealing with electric dinghy propulsion,  there is some advantages over the gas powered small outboards due to the simplicity , as long as you have the ability to charge them.  Charging with solar can do the job when you are in remote areas. But thats not instant like gas powered outboards if you run it on empty.

 

Lille , great shot, enjoy your trip in the Windward Islands, wish we were there . Everything electronic continues to evolve at a break neck speed.  When using lithiums, keep in mind that cold temps can restrict recharging too on some brands.  The earlier versions came with a feature to warm them.  On the opposite side you can install them inside, sideways without the same problem as lead acid batteries.

[Aphers]

I would never buy a lithium battery without doing due diligence on the quality. Ideally you want to see a tear down video so that you know what's inside it. 

 

I have built two lithium batteries from bare cells. It's not especially difficult. I did it primarily to save money, but it also allowed me to specify the type of BMS and the size/shape of the finished battery. The first one is approaching four years old and has been in daily use delivering hundreds of amps, powering an induction hob, air fryer etc, with zero degradation evident. It's remarkable technology.

[Oyster]

10 hours ago, Aphers said:

I would never buy a lithium battery without doing due diligence on the quality. Ideally you want to see a tear down video so that you know what's inside it. 

 

I have built two lithium batteries from bare cells. It's not especially difficult. I did it primarily to save money, but it also allowed me to specify the type of BMS and the size/shape of the finished battery. The first one is approaching four years old and has been in daily use delivering hundreds of amps, powering an induction hob, air fryer etc, with zero degradation evident. It's remarkable technology.

Can you tell us more about your considered AH rating and the physical size of your battery?  Any pictures? That sounds interesting.

[Aphers]

2 hours ago, Oyster said:

Can you tell us more about your considered AH rating and the physical size of your battery?  Any pictures? That sounds interesting.

Sure, although bear in mind this is as my yacht's domestic bank rather than electric power for the dinghy. 

 

Each battery is four cells and a BMS, the first one was 271Ah and the second was 280Ah. Both BMSs are rated for 200A, so in theory I can draw 400A total from the system. The cells themselves could support 550Ah total current. However I have the system fused at 250A using a Class T fuse (an important point- other high amperage fuses are not rated for large lithium systems). Each lithium battery is separately fused with a 225A MRBF as well.

The biggest draw is the 3kva inverter which can draw up to 240A, although I try to keep everything below 200A.

 

As to physical size... I can't remember off hand, but each battery is similar in size to a 110Ah lead acid. Certainly far smaller than 'drop in' lithiums of comparable capacity. They're buried under a berth in our spare cabin and not easy to access, otherwise I would measure them. 

 

Assembling the battery takes a few days but isn't difficult. You need you charge the cells up to full and get them all balanced. I used a cheap adjustable DC power supply. Then it's simply nuts and bolts and a few crimps.

I used threaded rod and plywood end plates to clamp the cells together, with the BMS mounted to one end. 

 

There's a lot of info out there on DIY battery assembly if you're interested.

[Oyster]

That's great information. My interest is for our rv, which is now set up for off the grid boon docking.  I have followed this now for a few years and with three different solar packages that I have built up and installed myself.  Lead acid batteries are heavy, if you get enough ah to run the essential stuff and run my 2000 watt Renogy inverter for a period of time without using the generator for a boost. Since the industry has removed propane fridges from the market for the newer rvs, and replaced them with the 12 volt sorry and still serious draw of current and questionable in dependability, I switched my setup to a residential, but similar Cu.Ft and run it on my inverter. So far , so good.  So I want to improve my setup after doing several trips with the current solar versus battery capacity without overloading the rv with dead weight.  

 

But the more reasonable lithiums, which reduces a ton of added weight on my hitch while the need to have the lead acid stored in the open area keeps me looking for a reliable and dependable alternatives from the current GC2 6 volt batteries.  I was able to achieve a decent AH for the limited room for open storage on the hitch.  The main issue with the AGM batteries , which can be stored inside and further back from the hitch are still heavy when I get enough AH to do what I want by batteries to do.  Thanks, I will look further into this , using what you have described. 

[Aphers]

Weight is just one of the advantages of lithium. I'm talking here specifically about LiFePO4, not the more high performance and dangerous stuff like Lithium Polymer. 

 

You can use pretty much the whole capacity of a lithium battery (vs 50% for lead acid) so not only ate they lighter, you need half as many Ah to begin with.

They hold up their voltage really well under heavy loads so no more low voltage faults from sensitive equipment.

Lithium batteries do not reduce charging speed as they fill up. So no more watching for batteries to go on float at a trickle charge rate. When you're charging from solar or a generator, you don't have endless hours of charging time available. 

Even if you don't get them back to full, they don't care. Lead acid batteries must regularly get back to 100% to prevent degradation.

You get far more charge cycles and many more years of use from lithium batteries. Cheap 'leisure' lead acids give you 150 cycles, high end AGM might get 500. Lithium is in the thousands, I've seen figures anywhere from 2000-5000 quoted. The first person to document fitting LiFePO4 to his yacht was Rod Collins, who after 13yrs has not been able to measure any significant loss of performance.

 

My lithium batteries cost less to build than the deep cycle lead acid I had originally planned to install- and that was four years ago. It's really a game changer.

[Lille Ø]

On 4/26/2025 at 9:05 AM, Oyster said:

Lille , great shot, enjoy your trip in the Windward Islands, wish we were there . Everything electronic continues to evolve at a break neck speed.  When using lithiums, keep in mind that cold temps can restrict recharging too on some brands.  The earlier versions came with a feature to warm them.  On the opposite side you can install them inside, sideways without the same problem as lead acid batteries.

Thanks! Little risk of the batteries getting too cold here.

We've lived on board through three Northern European winters (including freezing in for short periods). Our simple-but-efficient solution was to place the LiFePO4 back on top of where the diesel heater duct runs into the cabin. This means that even on cold days the battery compartment stays at least 15°C.

 

This of course wouldn't work on a boat that's left unheated. Then you'd probably want to take the batteries off and store somewhere warm, or at least detach all charging sources (LiFePO4 can be discharged colder than charged).

 

Today it is time to head to the chandleries. With only oars, our anti-theft solution for most of this Caribbean season has been to just tie the dinghy and take the oarlocks with us. But now that we have the outboard, we're going to want to lock the dinghy when we leave it. Here's the inital approach:

[Bryan Rolfe]

Hope you're enjoying the islands, and getting some time to go north before the hurricane is fully upon you. I really in enjoyed Dominica -- not the best anchorages, but it's a fantastic island to explore and much less developed than some of the other ones. Also if you haven't already, the Tobago Cays in the Grenadines are absolutely worth visiting. 

Might be worth adding a bow eye or similar that you can attach the chain to instead? Going over the hull like that I think you'll get chafe. When I was in St. Martin, with an old dinghy and a 2.5HP outboard, I walked up on a guy trying to cut through my chain and confronted him. He straight up tried to tell me it was his dinghy. Like you, I'm sort of hoping that a hard wooden sailing dinghy is not a desirable target for thieves, but the outboards surely are. 

[Bryan Rolfe]

Though I waffled back and forth on this for a while, I decided ultimately to go with an electric outboard, at least for now. If we feel like we need a small 2-stroke, I'm confident we'll find one 2nd hand very cheaply once we're in Mexico. 

I took it out for a little 5NM stroll through the estuary where our boat is kept. Was really satisfying, I can't believe ho quiet these things are. In fact, the noise the water makes against the hull is far louder than the motor itself, especially at the speeds I was running it (100-230W for 3-4kts).  

 

I do need to come up with a bracket for it to mount on. Today I used some plastic material so I wouldn't damage the relatively soft wood. Unfortunately the rudder gudgeons are bolted through basically right where the bolts need to be for the engine mount, so I think I will just 3D print something with ASA (UV resistant) that slips over this bit on the inside, and maybe a thin metal plate on the other side. 

Or I could swithc to screws... I thought there was a good reason I through bolted them, but I really can't think of the reason given the force on the rudder is so minimal. 

 

 

 

[Aphers]

You could just mount the motor off centre. That's what I do with my 3.5hp 2 stroke, and it allows me to keep the rudder in place. For a long motor I take the rudder off as it's easier to just steer with the motor. 

 

I've found that they noisiest thing about my Spindrift when motoring is the captive rowlocks which rattle like crazy.

[Captain Tim]

This guy doesn't seem happy with the electric outboard. "Trading the ePropulsion Electric Motor for a Loud, Smelly Gas Engine (But At Least It Works)"  

 

[Bryan Rolfe]

Yeah every new technology has its hiccups, and it's too bad e-propulsion doesn't have replacement cables/connectors, as I do see that as a vulnerability too. 

Gas outboards have been around a lot longer and improved over decades to (mostly) be reliable and low maintenance. That said, I've had to re-build carbs in many exotic places. We're leaving the option open for a gas outboard, preferably a small 2-stroke, but we're going to give the electric a shot until it stops working, or proves itself incompatible with our needs. 

[Lille Ø]

On 5/11/2025 at 2:49 AM, Bryan Rolfe said:

Gas outboards have been around a lot longer and improved over decades to (mostly) be reliable and low maintenance. That said, I've had to re-build carbs in many exotic places. We're leaving the option open for a gas outboard, preferably a small 2-stroke, but we're going to give the electric a shot until it stops working, or proves itself incompatible with our needs. 

I think a big difference between our Spindrifts and a deflatable is that for us the outboard is mostly a convenience, not a requirement. If the outboard doesn't work, we can still row and sail beautifully. They can't.