For decades, gas was the only game in town for propelling a boat. Not anymore.
“When I started working for Mercury,” Rushforth said, “they told me boats were about 20 years behind cars with regard to technology. But recent innovations have considerably closed the gap.”
The biggest difference between the two industries is research and development money. Even though a company like Mercury has spent about $1 billion on R&D over the last decade, it pales in comparison to the Volkswagen Group, which spent $15.2 billion in 2017 alone.
One sector of the auto industry that’s been booming is electric-powered vehicles, and companies such as Torqeedo, which makes electric motors for boats, have been beneficiaries of the auto industry’s research. Torqeedo partnered with fellow Bavarian company BMW to develop batteries for use on its larger motors. Since 1859, the lead/acid battery, invented by French physicist Gaston Planté, has been the go-to technology, but recent developments with lithium-based batteries have made them a viable energy storage medium. Among their biggest attributes are the fact they can maintain a high current, they don’t lose charging capacity and they provide far more charging cycles than lead/acid batteries.
This year, Torqeedo unveiled its largest inboard engine ever, the Deep Blue i 2400 rpm. It produces 100 kw (134 hp) and uses the Deep Blue BMW i3 battery, a 360v battery that has a 42.2 kwh capacity. The battery’s only downside is it weighs 613 pounds, which for its power output is actually pretty svelte. But in applications like ski boats, weight can actually be a plus.
The concept of an all-electric ski boat has been proven viable by Correct Craft. In 2011 it unveiled the Ski Nautique E, which was used at the 52nd Masters Water Ski & Wakeboard Tournament. Its most recent model, called the GS20 Electric, was introduced in 2017. It packs 220 kw (295 hp) of thrust and uses a 100 kwh battery bank, which gives it about two and a half hours of running time. The time to recharge is one to two hours. The downside? It costs $250,839, but it can go where gas-powered boats aren’t allowed.
This year, Mercury unveiled its first propane-powered outboard, a 5 hp model. I tested it on a 12-foot Jon boat on Lake X in central Florida, famed for hosting super-secret tests and used often to dial in racing boats. Given its top speed of 17 mph, it was probably the slowest non–human powered vessel ever run there. The Mercury 5 hp Propane FourStroke shares the same platform as the Tohatsu/Nissan 5 hp motor, and it started quickly, ran well and had snappy throttle response. Right now, Lehr has the most powerful propane-powered outboard, a 25 hp model.
The beauty of propane, aka liquid petroleum gas (LPG), is it doesn’t degrade and doesn’t have ethanol, which boat motors hate. In other words, if you left a tank of propane at the lake house all winter and came back in the spring, you could hook it up to a motor and pick up right where you left off in the fall, without any deleterious results. As an added bonus, it can pull double duty at the barbecue grill.
It really makes sense on a sailboat with a kicker, because the owner doesn’t have to keep six gallons of sloshing flammable liquid on board. Another benefit of burning propane is its lack of harmful fumes, which is why a lot of forklifts that operate indoors use propane.
Many boaters have learned — the hard way — about the detrimental effects of ethanol. And the strong corn lobby has been working hard to get the ethanol level raised at the pump, from 10 percent to 15 percent, which most marine propulsion systems are not designed to handle. There is a viable alternative that’s also renewable but doesn’t feature many of ethanol’s harmful attributes: biobutanol, the renewable form of isobutanol.
First, biobutanol is not a solvent like ethanol, so it doesn’t destroy rubber hoses and plastic or fiberglass fuel tanks, nor does it clean crud off the surface of internal parts and suspend them in a solution where particles can clog carburetors and fuel injectors. It also doesn’t combine with water, which, over time, will cause an ethanol/water mix to sink to the bottom of the tank where it can be picked up and burned. Because this nasty mixture is hyper-low octane, it can cause an engine to blow up.
Biobutanol can be made from non-food materials such as corn stalks, wood chips and switchgrass, and it can even be made from corn. It has a 30 percent higher energy content than ethanol, so its use actually improves performance and fuel economy, unlike ethanol, which lowers gasoline’s performance when added. B16 is currently being produced, but it’s for off-road use only, so it’s made in small amounts. The EPA allows just 12.5 percent of it to be added to fuel at the pump, so none of it shows up at the local gas station. B12.5 has been sold as boat racing fuel by Gulf Oil under the trade name Gulf Marine 100 at select marinas. Since it doesn’t absorb water, it has a shelflife of two years.
Both B12.5 and B16 are more expensive to buy, because they are produced in low volumes, not because they are inherently more expensive to produce than ethanol. The EPA has been considering allowing B16 at the pumps but no action has been taken thus far.