The mass of the motor itself isn’t really important. The main problems are:

• The battery mass and cells management. 21700 lithium‑ion cell cells are quite sensitive when soldered into a pack. A few cells for an RC model or a trials motorcycle are easy, but when you have several tens of thousands of them, you can definitely expect quite a few defects—both in the joints and in the cells themselves. How do you repair that…?
• Sealing the motor so that condensation absolutely cannot get inside. And it will be a bigg temp. changes there.
• The mechanical design of the drivetrain to be light and strong enough.
• Choosing the drivetrain layout — direct drive or drop-down.
• Cooling of the controller and the motor.
• The construction of the powerboat hull, from the battery section to the drivetrain, so that it can handle the additional mass.

In my opinion, you can expect the final cost of the conversion to be at least €200,000, and that’s a very expensive project for such an old hull.

For that kind of money, you could buy new engines, drives, and enough gasoline for the rest of your life. And you would probably still cause less environmental damage than by using:

• An electric motor who containing environmentally problematic materials for permanent magnets.
• Li-ion batteries, whose production is also environmentally questionable. (In China—Inner Mongolia—I saw with my own eyes what lithium extraction does to the surrounding environment!)
• Electricity from Germany, which is in reall actually in wery high % generated from non-renewable sources: a significant portion is bought from Poland (coal) and France (nuclear-ok for me, but not for your politicians), as well as from gas.

I think this would be a very expensive and inefficient toy, which unfortunately might still be used to obtain EU non-repayable funding.

Hi Plavutka,

you are with most thoughts right I think.
Battery pack manufacturing is not easy, ah and you forgot it’s also dangerous because there is always voltage. The Battery management is also a nightmare. I had the luck that I could develop and produce the bms circuit boards in my company. My experience was that the cells were always good even over the years. When a battery pack was dieing it always started with a broken BMS. Also as usual the guy who made the development of the bms quit the company. 😠
the welding of the cells was actually not that big problem. I will attach a video where if possible, a CNC router did the welding. I just found this video now the speed was much faster after some time.

Unfortunately I can not upload a video.
https://cimg6.ibsrv.net/gimg/www.off...83b498f13d.png

I know cells 21700, I use EVE INR 21700 50PL in my RC airplanes on the cells limits which it is in reall on 125 A. For the small hotliner with 1-2 S prop work I go over 200A.

Conerning the motor design, my thought was that the motor should have similar torque and motor speed then most boats with Z-Drive have at the propshaft. The problem is that all motors I found on the market have higher motor speeds. If you take a Tesla Motor eg. it has about 15,000-19,000 rpm, so gears are needed to get the propeller shaft speed down(3500 rpm) and torque up. As far I understood from my motor bike experience gears take efficiency and most times gears do funny sounds, also gears have a live time and need service like oil changes. I just repaired my rock hidden TRS lower gear housing on my 33 cougar and the oil situation was a real mess. Back to the motor, the only motor I found was the EMRAX which has also lower speeds. But the design is not really what could be under water. The price of the Emrax is also not really cheap and then I would need to build around another housing to use it under water.

@ Andrew and Smarty: I will attach the offer and the datasheet of the Emrax. Probably you know it already. Offer can be automatically generated at the Emrax homepage (www.emrax.com). Without controller!

To put the motor outside the stern in the water would have some advantages I think. No separate cooling, no impeller pump, the old engine room will be free for batteries, no joint shaft. Drives could be also trimmed up. If I crash the propeller and the finn it will be easy to repair!

https://cimg6.ibsrv.net/gimg/www.off...a502960c7f.jpg

https://cimg2.ibsrv.net/gimg/www.off...de21e30c52.jpg
https://cimg3.ibsrv.net/gimg/www.off...4c3497b5d3.jpg

@ Plavutka: Concerning China. I was always a fan, but since I orderer a metal laser cutter and laser welder in China which was was cought from German Custom and sent back I think different. The Chinese send me the wrong CE-Declaration so all went back and money was gone. Anyway I was asking Suzanne to offer me some Chinese 300 hp electric Outboards. I attache pictures. I just saw that the chinese calculate in the 1200hp system with a consumption of 7,5 kWh per km.
If I go on with this project then I would like to it without china. Batteries from Corea or Japan. The only thing I will order would be permanent magnets for the motor.
https://cimg1.ibsrv.net/gimg/www.off...b02dfdc859.jpg
https://cimg2.ibsrv.net/gimg/www.off...ccdadd2e1f.jpg

I mentioned China because practically all rare earth elements used for electric motors with stronger permanent magnets, and practically all the materials for manufacturing Li-xx batteries, come from there, regardless of where the final product is made. Even these 21700 batteries are actually from there. Unfortunately.

And this datas from outboard broshure are classic bull****!

1.) 360 KWh it is like 480 Hp. Gasoline engine with 480 hp use less than 145 l/h with this power. It mean that 360 KWh batery it is equivalent to 145 l or less l gassoline.
2.) 540 KWh it is like 725 hp. Gassoline engine with 725 hp use less than 220 l/h, probably less than 200 l/h, but ok. It mean, that 540 KWh it is equivalent to 220 l or less l gassoline...
3.) 720 Kwh = 945 hp = 280 l of gassoline and not 480 l.

And you can not take out 100% energy from batery.
Al this datas are like bad joke for boat wit si high instaled weight only for propulsion. It is limited ok for displacement boat
And wery high weight of batery also take a lot of energy by planing.
Electric power=no go for planing boat, except for speciall conditions, lakes, green fanatics...

I have an electric robotic mower that works great. Got rid of a crummy old zero-turn rider with a 20 hp Kohler Magnum and never looked back.

Blowing leaves is so energy inefficient, though, that electric blowers need too frequent battery changes when you need to move large amounts of leaves, e.g. when clearing a road through a forest in the fall. I bought the biggest backpack gas blower that money could buy at the time. It sucks down fuel at a rate which people not used to supercharged big blocks would consider amazing.