5 Myths with Electric Propulsion: Don't Believe Marketing

Electric power and electric propulsion are still growing industries for yachts and small ships. In this field, a few marketers may stretch the truth a little to make a sale. This led to many myths and misunderstand about electric propulsion. Today I debunk five common myths.

Note that this video does include several simplifications and details not covered for brevity. For full explanation, commission a custom engineering analysis from DMS.

References

[3] United States Environmental Protection Agency, Analysis of Commercial Marine Vessels Emissions and Fuel Consumption Data, Washington, D.C.: EPA420-R-00-002, February, 2000.
[8] A. D. S. e. al., "Analysis of The Propulsion System Towards The Speed Reduction of Vessels Type PC-43," International Journal of Engineering Research and Applications, May 2017.

[GeorgeOu]

Hybrid systems are probably the best of all worlds. Using the electric drive for slow maneuvering and idle is really efficient where the dirty diesel engine is extremely inefficient. But the diesel is really good for sustained 60% loads. This method does not add too much battery weight.

[mozismobile]

Electric is more complex to people who haven't dealt with them before, but infernal combustion has a lot more moving parts and needs a lot more servicing. Especially in small boats where changing oil and fuel filters etc is a hassle because they don't have full time mechanics on board. The maintenance schedule for an electric motor is "make sure it's still there" rather than the long checklist for a diesel.

Now all we need is a battery with the energy density of diesel...

[albula]

All good points. Battery is overall useless for boats/ships, except for ferries. I am certified on a few here in Norway and they sure are amazing machines.
What I would disagree in your video is complexity. With modern equipment, batteries are actually quite simple .They are different but there are almost no moving parts, no oil changes, no leaks, no fumes, almost no maintenance. You need some controllers to supervise the battery with loading or discharging but that's it. Also modern Li ion batteries are holding up fantastically for the absolute abuse they get on our ferries. We charge them with up to 4 MW every 30 minutes but they barely degrade.
The major downside is simply the range, that's why all Norwegian ferries that have plug in electric systems (about 64+) only one is without combustion engines. All other ones have 2 backup diesel generators to help when power is low, converting them to peak shave diesel electric propulsion systems.

[drchill]

For a video that purports to disprove myths, this certainly seems to intentionally walk right by the reasons why people choose to go electric, the sorts of boats being made electric, and the economics behind going electric. You imply that most people converting are doing so because of their concern for CO2 production, when very few people I'm aware of really care much about this issue. I mean, you know, we all want to do our part, but that's not what's driving us. We're changing because as recreational sailors and cruisers we are tired of the complexity, maintenance and expense of diesel power. Diesel's great, when it works. When it doesn't work - which is often - it's a royal pain. Mechanic's time, when you can find them and get them to come, costs a fortune. The engines are enormously heavy and located in cramped compartments and it seems that the part you need to get to is always impossible to get a wrench on. For every green warrior converting to electric to save the planet, there are five people who decided to go electric after hanging upside down trying to bleed the injectors while bobbing around out there, or spending two hours hanging upside down over the back of the engine block trying to replace another damned belt that shredded. The engines are dirty and noisy. The fuel is increasingly expensive, and finding decent diesel in some places is difficult. And when you get a bad batch in the Bahamas or Lewards you're dicked. And when your engine decides to have a fuel issue it always seems to be someplace dark as you're going into a channel with wind against tide. I like being able to simply push the throttle and feel the boat move. You talk about electric adding complexity. This is simply ludicrous in the real world. Diesel motors, especially the newer ones, are hugely complex with multiple potential points of failure. Electric motors have very few moving parts, and the components that run them are quickly and easily interchangeable because they are easily accessible and don't weigh much. Electric motors are torquey and deliver umph way down in the rev curve and they are extremely reliable. The only disadvantage to them, honestly, is range. Shrug. Some of us are still actual sailors. We sail. And your comment that running solar slowly doesn't have the math behind it is absurd. KWs are KWs, and if I have more coming in than going out, I can do it practically forever. For free. The cost of repowering with a new diesel is prohibitive. A new electric motor with battery system and inverter and charger will run less than half the cost of a new Yanmar. For a power boat electric makes very little sense (outside of narrow niches like canal boats). But I think that most people going electric are sailors. For us there are significant advantages you are ignoring.

[JohnWilkes-tbvc]

I watch many sailing channels on YouTube and observe that sooner or later every one has problems of some kind or other with their diesel engines . While this makes entertaining viewing is it the best method of propulsion for a sail boat? Combustion engines are highly complex with thousands of different mechanical and electrical parts. There is so much that can go wrong and inevitable they do even though they are being regularly maintained. An electric motor has very few moving parts and much less that can go wrong. A BLDC electric motor has basically two bearings at each end of the shaft for moving parts and not a lot else. In contrast a diesel engine has pistons pounding up and down, bearings, gaskets, hoses, cables, pumps, filters, cooling, alternator etc all of which sooner or later will fail. A diesel engine requires regular maintenance whereas an electric motor requires minimal maintenance.

For me an important factor is that once on an ocean passage you cannot stop mid ocean and top up the fuel tank. With electric there is usually a daytime charge from solar especially in the tropics and probably regeneration from sailing if on longer passages. If range is a problem than just add more battery capacity and more solar. I agree lead acid batteries are heavy but lithium are not. If a boat goes to electric drive it makes sense to replace the batteries with lithium and use some of the space and weight gained to increase the battery capacity.

Depending on the size an electric motor it can often be lifted by hand and is much lighter that a diesel engine. In contrast look at some of the videos of people removing a diesel engine from a boat using all sorts of lifting tackle to get it out safely. Removing the engine and diesel tank will not only reduce the weight of the boat but provide additional valuable storage space as a bonus.

To me it looks like going electric is a win win situation and that is before adding the benefits of silence, no fumes, no dirty bilge, no smoke and no smell.

[katanaridingremy]

I think the biggest mistakes when considering electric boats is that all boats are still made as if they are using ICE engines. Few are getting to innovate the marine space like Tesla is the automobile and SpaceX industries.

Instead of treating batteries as if they are replacing a fuel tank, design batteries as part of the superstructure itself. Any weight batteries add is minimized as being part of what holds boat together. Why, rely on solar to charge batteries when you can also have wind turbines. You can also use aquathermal energy (same as geothermal) to generate electricity from the difference in temperature between the water and air, which would be perfect for a constant trickle of energy always going into batteries. Further, when anchor or docked you can lower small turbines into water columns or tides and capture energy from there. Lastly, there's the ever present kinetic energy from waves. Just like how sidewalks are designed to capture energy from people footsteps, the hull can be designed to capture energy from the water making contact. If there ever was a more perfect solution for self sufficient travel it's the marine sector, it just requires thinking outside the narrow box of historical boat production.

[RulgertGhostalker]

direct drive only works for lighter craft with lower power requirements..
the more weight you have to push, the slower the prop needs to spin to couple with the surrounding water under those loads.

that said, not all electric motors are created as torque equals ... the axial flux pancake motors put out more torque per volt.

[freelectron]

Electrical engineer, So many things wrong here. I can't even begin to be bothered starting . Some one please help me out here

[brentsinger]

Enjoyed your video, really valid points. I sell electric motors & batteries and we often tell people that there are parasitic loads on smaller motors (<50HP), i.e. alternator, water pump, and this means the number on the cowling is not the HP delivered to the propeller? Do you think this is a truth? And we also say there is a better 'feeling' to a flatter electric throttle/torque mapping. The effect goes away sharply as you approach 50HP.

[shaider]

For electric motors, their power is equal to voltage times current. A high voltage motor will run faster but has small torque and vice versa. Joule heating is related to the current. Hence, a high speed motor stepped down via gearing is preferred to a slow one

[skylerstevens]

I'm totally imagining Galaxy Quest with Tim Allen shouting keep the boost on for "Peak Power"

[wrobelda]

Which 10kW electric engine weighs 134kg?! Seriously, which one? Also, 60kW battery bank weighs 340-400 kg. So the batteries in this case would amount to 2400 kg at most. 6750kg?! Again, where are these numbers from? You even show a car better by bank, which are exactly as heavy as I said.

[youruiz]

When it came time to repower my Valiant 40 sailboat, I first looked at upgrading the original Westerbeke diesel to a Betamarine diesel but it would take at least 6 months toget the motor from the manufacturer and then 3 to 6 months to have someone install it at a total cost estimate of $38 to $42, 000. 2023-2024 saw LiFePO4 cells drop drastically in price. One can DIY a 51.2 nominal voltage battery totalling 16kW for less than $3000. I was able to build an OceanVolt ServoProp 15 based system with 3 x 16kW batteries (48.2kW), doing all the work myself except for the hull glass work for converting from shaft to saildrive. The total cost was $57, 426. I no longer need to do any maintenance except zincs or worry about bad fuel stalling me out (happened to me twice). Reduced weight by 592lb (full tank wt). There is no diesel/oil smell anymore. Motoring is completely quiet. Gained a large storage space under cockpit where fuel tank used to be. I never have to buy or treat fuel. My galley is 100% electric since I could get rid of propane. I can motor for over 8 hours at the same speed I used to on diesel before having to worry about battery. Best of all I get ~400W recharge while sailing 6.5kt. The ONLY benefit diesel power had was the ability to motor 400 miles on a tank and be able to fill the tank in 30 minutes. Now I can motor 50 miles and it takes all night to fill up but I have never in my life motored more than 50 miles in a day so it works out for me :)

[davidotness]

Well, I'm already ahead of this in my project, a 42' motor sailer. I already am to the point of wanting/requiring a generator for backup, 120/240 power, and hydraulics, a product of my 60+ years at sea commercial fishing and sailing merchant marine, mostly in Alaskan waters. As you can most likely tell, I'm retired, so fast speed is not a need; always watching and anticipating the weather is imperative for my cruising plans.
Glad you made this for "to whom it may concern." My larger issue remains what type of battery system to invest in, I've heard some horror stories using lithium batteries that spontaneously combust. I'm open for comments regarding their safety record. And---Toyota seems to be leading in a next-generation battery using silver as the medium and it sounds very encouraging for not only safety, but very rapid recharging, much better than lithium. Caveat: yes, it remains to be seen, but it's sounding quite likely.

[FainTMako]

Lol, I love this channel. Thanks for bringing some personality in with all the useful information you present.

[MurkyDregs]

Very much a layman question here. I'm in the process of having a boat built, 29' DE type, inboard, 270hp diesel spec'd currently.

As I understand it a diesel prefers to operate in a given range for maximum efficiency, yet a hulls most efficient performance, (in terms of fuel consumption, is "hull speed." Hullspeed tends to require a far lower power requirement that's lower than where the engine is at optimal performance. Does a hybrid solution address this mismatch?

[franciscomartinezzea]

Hi. Do you have a video on cycloidal propulsion? What are your thoughts on this system? I've seen them used in tugboats and corvettes...

[TyinAlaska]

I'm waiting for solid-state batteries... and millions of dollars. 😆

[dandil]

wait but when a car says "200hp" or whatever that too is peak power; if you ran that engine at peak power RPM and full throttle you'd get a very reduced lifetime. Also yeah power is power, but in many cases the availability of max torque at any RPM makes vehicles accelerate harder in the real world. "holeshot" with a jet boat for example is easy to do with electric torque and can bog down an equivalent hp ICE engine.

[ricardodelzealandia]

I don't disagree with any of this, but the table at the beginning is not factoring in that any diesel boat will have at least 1000L of fuel (at least as a capacity) so there's that weight to consider. Battery weight is high but if you have a large fuel tank, you could be matching battery vs fuel weight. In addition, all boats have batteries anyway so the difference in battery weight will be the maximum battery weight needed for the engine minus the battery weight already planned.