It had to happen eventually. With all the electric cars hitting the market, somebody with dollar signs in their eyes would stick the same batteries into a boat, and sell it to the aquatically inclined. The electric motors for boats you are undoubtedly already familiar with are just piddly little trolling motors, I'm talking full blown high speed motor boat propulsion instead.
If you're looking to convert your existing boat, Torqueedo has you covered. Offering motors anywhere from 1 to 80 horsepower, they can electrify watercraft from your fishing dinghy all the way up to a small yacht.
They also have loads of surface area to slap solar panels onto, allowing them to "refuel" constantly while away from the dock. Gas boats can't do that. And with enough panels, you can power the motor directly from sunlight, not using any of your battery capacity at all until the sun goes down.
On the high end of the market, we have Edison Electric Boats. All polished wood body, twin 70kw motors, a top speed of 40mph and a range of between 30-40 miles depending how it's driven. This is the Tesla of electric boats. You can increase the range by buying a larger battery pack, but the stock configuration is already $120,000.
Heartbreaking isn't it? But marine applications are very demanding, it takes more energy to push a boat through the water than to propel a car of comparable weight across land. The limit is also economic, not technological.
Due to the high buoyancy of air, boats can carry extremely heavy loads. You could pack way more batteries into this thing than it comes with, it would just cost an arm and a leg (which it already does). The price will come down though, thanks in large part to the growing market for electric cars.
"I don't want to hear it" you say. "That's too rich for my blood". Fair enough, I said from the start that it's at the high end of the market. If what you're after is an affordable electric runabout just for traveling between your cabin and a buddy's, or going to the marina to buy groceries, consider one of Go Float's offerings.
They may look like toys, but the nicest one will do 25mph. That's nothing to sneeze at, you can pull a water skiier at that speed. In terms of speed, the nicer models at least are real boats. You can go usefully fast and far in one of these, but it'll only fit one or two passengers depending on the model.
The cheapest one, still a few thousand bucks, will do around 4mph, with a range of 6 miles. Optionally you can add a second battery to double the range, and the batteries are hot-swappable. This means you can remove the depleted one, put it on the charger, and put the freshly charged battery into the boat so you can continue your fun without having to wait.
The biggest advantage is the relative lack of maintenance compared to gas powered boats. Brushless electric motors are maintenance free. There's no fouled plugs, no timing issues, just charge it up and go. If you leave it sitting outdoors you may have problems with the battery, as freezing temperatures will damage it, but that's about the only consideration.
At the lowest end, it's feasible today to build your own solar electric boat. It won't be pretty or move terribly fast, but trolling motors consume sufficiently little energy that it's quite easy to power them purely off solar. You should still carry a battery with you in case the weather turns bad, but so long as the sun is shining you have effectively infinite range. You can get anywhere you please, just not in a hurry.
Jamie Mantzel, mad genius, role model and my favorite Youtuber currently lives in the Carribbean where he gets around using a solar powered boat of his own design. While the sun's out, the motor is powered only by solar. The batteries are only necessary to draw on as the sun goes down. The video above documents a thirty mile journey made using only the power of the sun.
If you have a boat and some cash to spare, or are just an eccentric hobbyist looking for a project, electric boats should be on your radar. Even totally ignoring the environmental benefits, some lakes don't allow motorized watercraft if they are gas powered, and such regulations are likely to become more widespread and stringent in the future.