Converting a direct drive ski boat from gas to electric

[cougfan]

Saw an electric Nautique wakeboard boat at the Seattle boat show this week. This got one of my ski partners and me to thinking what would it take to convert a direct drive ski boat into an electric version.

I remember seeing a thread earlier on BOS about an electric ski boat but don’t think it was a converted boat.

Anyone have any info on this subject?

My ski partner and I are up for the challenge. All we need is more info on the subject to see if it is feasible and or worth doing.

We both are mechanical, have the shop space and the time. He is also retired from Boeing in the robotics department.

Just thought it would be cool to have an electric ski boat on our ski lake.

Thanks in advance for any info?

[Andre]

http://www.ltsmarine.com/EN/

First Nautique ever converted was by LTS marine.

[DavidN]

Pricey, but probably the easiest way to do it...

https://www.thedrive.com/tech/30431/electric-v-8-crate-motor-from-electric-gt-is-sema-swap-ready

[Horton]

https://www.digitaltrends.com/cars/electric-crate-motor/

[Horton]

@cougfan You say electric Nautique? You mean from the factory standard equipment electric?

[MuskokaKy]

Doesnt anyone remember this? i thought it was pretty cool when i first saw this video in 2013.

 

[Horton]

https://www.instagram.com/p/B74z8zWBzRb/?utm_source=ig_web_copy_link

[Pullhard]

Recommend finding a wrecked 100% electric car like a Nissan Leaf and get the motor and battery out of it. Will take some ingenuity and fabrication to figure how to mount the motor. Next problem will be where to put the huge battery. Would also be some concerns about a large battery in the boat and coming in contact with water, fire concerns, and electrocution . Most also people don't know lithium batteries are highly flammable. Electric motors have huge torque and rev. Will need to figure out how to gear the motor down and what type of prop to use. Finally, the charge only last for a short while so recharging will also be a concern.

[6balls]

@Pullhard so no problem, right? Will keep putting gas in mine.

[BraceMaker]

@Pullhard think a leaf would have the necessary power? A basic leaf is like 150 hp. Maybe in something like an old stars and stripes but I'd be concerned it wouldn't give you want you wanted.

[jjackkrash]

@Horton, I was told approx. $300k for that 210, or only about a $200k upcharge over base 6.0l 210.

[Justin]

https://www.instagram.com/watershedinnovation/

[Jody_Seal]

Hey ! Dont forget cable skiing is electric..

[cougfan]

@Horton the Nautique was straight from the factory. Should have gotten pics but was too busy asking about the boat ☹️

We are thinking of using an older prostar or Ski Nautique as a donor boat and swaping an electric motor for the gas motor. Need to figure out the battery issues among other things.

We need projects in our retirement?

[Horton]

@cougfan as long as you are going in knowing it will be a huge money pit.

[BraceMaker]

I've been pondering this for a while. There is an old nautique atom skier so incomplete it will never get restored. An I do feel it would be a very cool electric ski boat. Small enough to run on a lower power cheaper motor. Atom skier appropriate in name for an electric boat. And since it's not a restoration the ability to use modern epoxy sealers and finishes would make the hull work easy. The power train being 15K has been off-putting.

[jayski]

https://correctcraft.com/correct-craft-acquires-electric-boat-drive-system-pleasurecraft-engine-group-prepares-for-the-future/

 

https://watershedinnovation.com/

[sixball]

I think one of the first things is to look at the weigh distribution on the current boat and understand somewhat close what you may wish for weight distribution. would not want to spend the time doing the build and then finding the wake is crap from the hull not sitting in the water proper. Then would you weight it with sacks to get a surf or board level wake? Once you understand that you will have a good Idea on the start to placement of the new gear. The battery's should give you a good start as the motor I would think will be lighter. You may need to think of drive shaft angle in that equation. Not going to be easy to make the hull work better then the manufacture. If you are going to do it the need to get it close is a must in my mind.

[cougfan]

We are in the early planning stages of this project! Seeing the electric Nautique boat at the boat show kind of sparked an interest in us. We know that it won’t be easy or cheap that’s why l started this thread to get all the info we can. I know of an older Ski Nautique that can be bought for cheap to use as a donor so that would be a start. Still researching the electric motor and battery set up

[Wayne]

My company has done EV conversions for OEM demo vehicles. Prices range wildly depending on the level of integration but the best advice I can give you is make the powertrain work before you buy a boat to put it in. The biggest hurtle will actually be the battery pack, charging and the Battery Management System. You can buy an inverter for a 3-phase permanent magnet motor from SemiKron and characterize it to a motor pulled out of a wrecked EV or use a take out electric axle from a car (Tesla model 3 axles run around $5k). Or buy an aftermarket inverter/motor from a Chinese company.

 

Horton is very correct this will be a money pit. Material costs for EV conversions, even using donor vehicle parts will go over $20k very quick. Add in the extra bits and a rapid prototype control unit to manage everything and $50k will be in the rear view mirror and $100k soon approaching.

[cougfan]

I know a retired Tesla engineer who opened up a used electric car / repair shop with his son. Will be checking with him about this project. Should be a great source of info and maybe parts. Stay tuned

[KRoundy]

@Wayne Yikes - that's an expensive retirement project. There's a reason Nautique did this in a wakeboard boat first - the weight penalty for a battery that lasts long enough for a ski is similar to fat sacks. @cougfan Would you consider a wakeboard project? Perhaps a Air Nautique from the 90's could be had for cheap?

[lakeho26]

Could the added weight of the battery’s be compensated with a lighter weight hull design? Such as the 176 at 2250lbs manufacturer’s weight rating of course but still lighter then current slalom boats. I understand current hulls are constructed differently with liners and different stringer designs but could a slalom tug be built lighter at today standards to compensate for the electric drive unit, including the battery, control, inverter electric motor.

[lakeho26]

I guess my comment above was slightly off topic but maybe starting with a 176 or similar weighted hull would be a good starting point!

[Horton]

@lakeho26 as modern boats have gotten wider and have a larger wetted surface area the acceptable weight range has gotten heavier. The ProStar has the largest wetted surface area of the current slalom boats so it could take the most additional weight with the least penalty. A smaller / lighter boat like a 196 would be much more impacted by the additional weight.

[cougfan]

@KRoundy not really interested in converting a wakeboard boat. The Wednesday night crew want to use the boat on our private ski lake for our Wednesday night skiing. Usually ski for 2-3 hrs so hoping we can get enough battery life for this. Like I said earlier this project is in the very early stages of research/development

[chrislandy]

I think it's a great idea, especially if you only have a few hours running at a time with a long break between,

 

I was thinking about it myself, but as I repowered mine last year it's thrown that idea out the window for a few years!

 

think tesla motor rather than nissan leaf.

 

Weight: not an issue IMO

 

LT-1 engine is circa 300kg wet, gearbox is approx 50-70kg = 350kg

Full tank of fuel, 100l, approx 100kg inc tank

 

Totoal 450kg

 

Tesla motor is about 140kg (everything bar batteries) - direct drive to shaft as it has a gearbox in it

Tesla batteries are about 25kg/unit, say 10 units = 250kg (aparently typical for a 200 mile charge range in an EV)

so thats about 390kg

 

So that leaves about 60kg (130lb) weight saving, or another 2-3 batteries.

 

You can unlimited water cool so overheating is not an issue, parts look to be about $30k from EVWest sso you could probably source cheaper if time is on your side

[lakeho26]

@Horton that makes sense and understood. Would a smaller wetted surface area of a 176 or similar weight ratio to wetted surface area boat, make it feasible for an electric drive unit to be efficient enough due to the lessened load on the drive unit to work? Or is the added weight to a smaller wetted surface area boat going to cause as much drag/load as a similarly weighted larger wetted surface area boat?

 

Understanding of course that the wake might not be optimal due the boat being designed with a different weight in mind.

[Pullhard]

Interesting photos and videos. That boat is full of batteries....Would also like to hear what it sounds like. Electric motorcycles and other electric vehicle conversions have a strange whining sound. Will take some getting used to not having the sound of a big V8 onboard. Would also be interesting to see how a perfect pass would work with an electric motor.

 

http://www.ltsmarine.com/english/lts-water-ski-boat/

[cougfan]

@Pullhard if you will miss the sound of a V-8 just get a recording of one and play it on your 8- track while you are skiing/driving??? Seriously wouldn’t Zero Off work in an electric boat?

Lots of questions left to answer but the list is getting shorter thanks to all of the responses ?

[KRoundy]

This year-old winter thread had lots of discussion and links in it:

https://www.ballofspray.com/forum#/discussion/20830/are-we-closer-to-an-electric-tow-boat/p1

[ozski]

All that money and expense at least go with a hull that tracks way better than the rest.

[Kwoody51]

I talked to one of their sales guys about their electric boat at the show in MN.

 

Said ~1.5 hour run time and will only charge at 60 amps or 14 kWh/ hour. Assuming a 75 kWh pack size (he didn’t know pack size) this means if it’s dead you are looking at 5+ hours to recharge. He said top speed was 40+mph, just like normal v drive.

 

You can get a complete separate battery pack installed on shore, for $60k, which will allow for much faster charge times.

 

Said they have this electric boat out for a customer on Tahoe. They had to adjust the torque curve as early torque mapping was leading to snapped drive shafts. I didn’t feel I should mention I thought that was across all V drive boats :)

 

Regardless of cost it’s cool to see someone trying something different. Clearly as the auto’s create large battery packs they will be utilized by others for other applications.

[Jetsetr]

WHY WHY WHY???

Reality check: you don’t have a green boat...

Where does the electricity come from? More than likely a coal fired power plant (gas or the N word).

Step away from the granola, adjust your beanie, slip on your Birkenstock’s and ride your bike to Starbucks for a grande mocha frappe chino mouse milk double lite whip for $14.

 

You’re NOT making a difference...

[AdamCord]

@Jetsetr You're right that EVs are responsible for carbon emissions, but even in coal and natural gas heavy areas, they pollute much less than gas vehicles. For instance, in your state of Wisconsin, where natural gas is heavily used for electricity generation, an EV still produces about half the carbon emissions as a gas vehicle.

 

 

Where I live in Washington we have almost 70% hydroelectric power, so an EV actual produces 13X less CO2 than a gas vehicle!

 

So even if we don't add any new renewable energy in the US, it's already much cleaner to run an EV. Right now it looks like there are going to be major additions in the next 5-10 years to natural gas and renewable electricity sources in the US (natural gas produces about 50% the CO2 as coal), so it will only get cleaner.

 

BUT that may not even be the main reason to drive an EV. You need to drive one yourself to experience how much better a simple electric drive system can be. You have just a few moving parts vs hundreds in the Rube Goldberg Machines that we call engines. No more oil changes, no more lugging gas cans, no more of the hundreds of maintenance issues that gas engines have. I also think that once we do get electric boats, the speed control system will work much better and give a better pull than what we have now. Oh and they are way cheaper to run.

 

Now with all that said, I think that similar to how boat manufacturers put Chevy engines into their boats, in order to get the price and performance where they need to be a boat manufacturer will need to buy the systems from an electric car manufacturer. That's where the economy of scale will drive the price down. I'm happy to see Nautique working on this, but if the prices stated above are accurate then it's a non starter. If Tesla is really able to come out with a sub-$50k electric pickup truck next year then I will see no reason why that tech wouldn't work in ski boats.

 

Source: US Dept of Energy https://afdc.energy.gov/vehicles/electric_emissions.html

[AdamCord]

Also it's good to see a visual representation of what CO2 emissions look like. I introduce, Car Turds:

 

https://video.whyy.org/video/carbon-car-tailpipe-solid-chunks/

[jercrane]

Honestly the most appealing part for me would be sound reduction.

[chrislandy]

It also depends how much petrol costs in your area, using a rough conversion of 1.3 exchange rate $/£ - it costs me $200 to fill the tank from empty and I'll get 4-5hrs out of that. To charge a 100kwh tesla battery would cost me $16 and get 200 mile range in a car (tesla), so maybe 2-3 hours in the boat (very rough guestimate).

 

So 4hrs running would cost me approx $25-30 rather than $200

[BraceMaker]

@Jetsetr - I don't buy into that argument, it ignores the energy input that is required to explore for, drill, collect, transport, refine, package, transport again, and finally distribute the fuel that we burn. If we use 4-12 KW of electricity in the ability to get a gallon of gasoline into your car all of a sudden that formula shifts.

 

 

[cougfan]

@Jetsetr you are missing the whole point of this thread! The main reason I would like to convert a gas powered boat to electric power is to say I did it. Really want the challenge. The benefits of having a green boat are all icing on the cake.

After reading the feedback on this thread I know it will take a lot of effort, know how and the biggest stumbling block of all $$$$.

I plan on asking lots of questions of people that know about electric cars. Some people have already reached out with offers of help on this project. I didn’t expect this to be easy.

After seeing the electric wakeboard boat that Nautique brought to the Seattle boat show and talking to a couple other venders that sold electric boat motors I thought Why not?

I don’t expect this project to be easy or happen over night.

And by the way I don’ even own a pair of Birkenstock’s, I don’t drink coffee or eat granola. I do wear a beanie on cold days to keep the old dome warm. Not as much hair on top anymore ?

Just my thoughts

[The_MS]

I will make sure to get my contacts at Zero Off to develop a program that will make it feel like a great pull.

[Bruce_Butterfield]

@cougfan while you’re at, another thing to consider would be a twin screw setup. There was a show skier in the midwest a while back that modified the transmission in a ski boat to drive 2 props. With the low rpm torque of the electric motor, it may be able to handle 2 props for better holeshot and better holding power in the course.

 

Obviously that kind of transmission would add a lot of complexity, so with electrics you could use 2 smaller motors and keep the direct drive. Probably a more reasonable design.

 

I’ve long thought a twin screw setup would have a lot of benefit for a slalom boat.

 

Just trying think of more ways to help you spend money?

[BraceMaker]

@Bruce_Butterfield - see my thought was sort of the opposite that you would probably save a lot of money going with a dual motor single prop combination. The cost of a single large motor in EV conversion is high compared to the cost of two weaker motors, add to that the ability to use a belt drive for gear ratio and the ability to spec props for relatively low cost and high ease through someone like @ojeric I think that would be the route.

 

More props = more turbulence, plus now you need to relocate and install struts/thru hulls, plus inboards don't reverse for anything if the rudder isn't in the prop wash so now you need two rudders... Just a nightmare.

 

Show ski is different where a 1:1 boat will rev to 4k and not pull a group off the dock. Don't need that for slalom.

 

 

[Bruce_Butterfield]

@BraceMaker, yes this is a big unknown where we are all speculating. There is a lot of trial and error to get close to something that works and we can all thank @cougfan for being willing to drop a boatload of $$$ on a fun project!

 

Backup and think about the differences between a car/engine and a boat. A car has nearly perfect traction (within limits) and a boat/prop is essentially spinning its wheels and boiling water to start and slipping the entire time in the course. If you can improve the "traction/efficiency" of HP to the water, it "should" result in a better pull. That's where more prop surface area comes into play. Whether a single Big Ass prop or a pair of more typical props is a trade off, but more blade surface area is better as long as the engine has enough torque to handle it without bogging down. That's where the low rpm torque of an electric motor has a huge advantage over a gas engine.

 

So if I were in charge and spending someone else's money, I would start out with a bubble butt Nautique, 2 electric motors and a pair of 668 props. Getting the right props for the engine/boat is a black art with trial and error. That's the starting point and I would try to get as much pitch as the engine's torque could handle.

 

Yep, 2 more holes in the hull and 2 more rudders. I'll wager the turbulence will be less than a single prop. I'll bet a case of beer on that, but not a paycheck.

[chrislandy]

@Bruce_Butterfield KISS comes into play here, proof of concept on one motor, get the motor controller working and integrated properly with a the throttle control and any speed control system (ZO etc) - @The_MS I suspect you could integrate the code directly into the ESC unit rather than having a separate module as there are a lot of open source motor controllers around now.

 

Then add another motor as a development project, I've seen some EV's have duel in line motors as well as separate wheel / axle drives. Getting two parallel motors synced up shouldn't be that much of a problem as most have rotary encoders on them to track rotation speed.

 

 

On a slightly separate but still on topic note, the UK are looking to ban the sale of petrol, diesel and hybrid cars by 2035 so developing a fully electric ski boat should be a priority. The rest of the EU currently being 2040

[Jetsetr]

All...just giving you all a bit of grief...

 

Wisconsin’s energy mostly comes from coal fired plants. The gas fired turbines are on demand/peak units that come on line as needed...home heating is probably split between gas and electric, probably slightly biased towards gas (much less expensive but some areas don’t have the infrastructure).

 

I TOTALLY get the “because I can” side of doing an electric boat. I’ve built many one of one projects (but they have paid for themselves and generate income for my company). I love doing something that people said can’t be done. That’s the driving factor for the E boat I’m sure. But a hour and a half usage and 4-5 hour charge isn’t going to work for most skiers. I’m sure there are peeps that just pull a few sets and are done. My boat is on the water all day and still uses less than 20 gallons of fuel.

 

I would do a single motor/prop/rudder first. You’re already reinventing the wheel to a point. The amount of structural mods alone needed to do a twin motor/prop/rudder is well beyond most solid builders/fabricators. Keep it simple at first...if there is such a thing.

 

It’s going to be HEAVY...Lithium Ion batteries are about 1200 pounds, motor 100 pounds all the junk to make work 75-100 pounds more...I think you’re over the hull weight capacity just with the batteries. The LI batteries were a comparison used in a EV. Probably find smaller/lighter but at the expense of usage/time.

 

Gas motor and trans 500 pounds.

 

Heavy = low in the water bigger wake...that displaced water has to go someplace.

 

It’s a good off season topic (at least where we can’t ski).

 

Back to the shop...building (another) Rolls-Royce Viper 601 powered 1940 Ford truck....???

 

Hugs!!!

[ForrestGump]

It needs to warm up so you nerds start skiing again and stop all this silly talk.

[Jetsetr]

@ForrestGump RIGHT???!!!!

[skier2788]

Since you are in Seattle.... I would start by talking to these guys.... Clean slate to start from and a proven hull. Design the interior how you want ....

 

https://www.ballofspray.com/forum#/discussion/20028/stolen-boat-from-the-hilltop-lake-arlington-wa-just-north-of-seattle/p1

[eleeski]

@Jetsetr I looked up the weight of a 5.7 engine at about 500 pounds to make sure my truck could haul them back from Texas. Once loaded, the mechanic looked at my flattened springs and squished tires and said "you know those engines weigh about 900 pounds as a marine conversion?" That was a hairy drive home in a massively overloaded Ranger. Traditional engines are quite heavy.

 

In a tournament environment, batteries could be replaced at short intervals with a quick swap system. Possibly expensive but certainly not a weight deal breaker.

 

Acceptance of electric boats will only happen with getting some out on the water. @cougfan 's project is worthwhile. Especially if things like motor and battery suppliers are shared with us. My 04 MC project is waiting for an electric conversion.

 

Eric