Transitioning from electric toothbrushes to electric outboards, a Washington couple developed a compact, lightweight, and simple-to-operate dinghy motor. We look at PropEle Electric Boat Motors Inc. and the secret behind going 1,000+ nautical miles on one equivalent gallon of fuel.
Gilching, Germany, and North Bend, Washington, might be 5,250 miles (8,450 km) apart as the crow flies via southern Greenland, but they share several characteristics. Both are exurbs of major cities, i.e., Munich and Seattle, respectively. Both are situated in proximity to lakes and mountains. And both places are home to makers of electric outboard motors.
Headquartered in Gilching, Torqeedo has been blazing a path for modern electric-propulsion systems in recreational craft for more than a decade. Today, with 200+ employees the company is now owned by Deutz, a large German industrial corporation.
North Bend is a whistle stop on I-90, on the west side of Snoqualmie Pass in the shadow of Mount Si, where Joe and Linda Grez, both in their 50s, hung out their shingle as PropEle Electric Boat Motors, Inc. They started with a small outboard for kayaks, called the Electric Paddle, but today they focus on a more powerful model, the EP Carry, a 220-watt motor for small tenders and dinghies that costs $1,600 with battery, comes in three different shaft lengths, and weighs 21 lbs (9.5 kg)—all included.
Taking on Torqeedo’s marketing and financial muscle and its established lines of Ultralight and Travel outboards resembles Grimm’s tale of the Valiant Little Tailor battling giants. While the Grezes acknowledge jousting for dominance in the market is not an option at this time, they see opportunities. What gives them confidence is their legitimate claim of “Assembled in the USA” and their thorough understanding of consumer products, having worked at Sonicare to develop and market the popular electric toothbrush. A search for Joseph Grez on Google Patents returns 54 entries. Most of them are for technologies related to skin-, hair-, and dental-care products, but three are for technical solutions for use in electric outboards, including a transom clamping mechanism (US8747171B2); a pivoting outboard clamp module (US20190061897A1); and the activation and deactivation assembly (US9004964B2).
Combining work experience, fastidious research, and their personal experience as sailors—they own a sharpie cruising ketch in the San Juan Islands—the couple believes they’ve found a sweet spot with fellow cruisers who want electrical power for the commute from boat to beach and back.
Exploiting a Niche
“We have a couple of things in our favor,” Linda Grez says. “People are dissatisfied with heavy weight, gasoline, and all the disadvantages of gas engines. The aging demographic of boaters doesn’t want to carry a 35-lb [15.9-kg] motor or hand it down to someone [in the dinghy], and younger people are very excited about electric technology.”
Another impulse came from shifting market conditions compared to a few decades ago. “Most [small dinghy motors] weighed between 14 and 20 lbs [6.35 and 9 kg], and sales of motors in the sub-4-hp range were almost twice what they are today,” explains Joe. Then more stringent emission rules effectively replaced those small two-strokes with bigger, heavier, and more-powerful four-strokes that weigh between 30 and 50 lbs (13.6 and 22.7 kg).
Convincing consumers that they don’t need oodles of horsepower to go from ship to shore and back when a small, quiet, and light electric motor can do the job still takes persuasion. Eliminating the hassles associated with combustion engines, such as emissions, noise, odor, oil changes, winterizing, and proper storage in a vented space, is helpful, but it does not eclipse a mental condition known as “range anxiety,” but more on that later.
The EP Carry, Joe Grez maintains, has “a reasonable amount of power for these small boats. And more power doesn’t make sense, so let’s focus on portability and ease of use. Of course, we don’t have the smoke and the choke and the stalling and the turn-it-around-for reverse. But that’s the game.”
It is a game with a growing number of converts, according to Stuart McKenzie of Comox Marine, PropEle’s Canadian dealer in Comox, British Columbia. “Our typical buyers are cruisers on smaller boats, both power and sail, but mostly sail. They like the compact, lightweight, easy storage and use of the EP Carry. To date I have nothing but positive feedback from our customers using the motor.”
Simple Is Hard
Aside from the selling points of all small electric outboards, the simplicity and the application-specific design of the EP Carry merits a closer look.
For starters, it uses an air-cooled brushless motor. There’s a shaft coupling between the output of the motor and the main shaft and a “rubber spider” connected to a rubber fan, which pushes cooling air over the motor and the heat sink of the controller before expelling it in the back.
The Grezes say it took them 18 months to figure out the key design considerations, which boiled down to two areas: Addressing the likelihood of hitting rocks in shallow water, and the stability issues associated with having to stand up in the dinghy to mount or remove the motor and to tilt it up and down.
The first issue was solved with a custom design made of fiberglass-reinforced nylon by APC, a producer of propellers for radio-controlled model aircraft. “These props are 70% glass filled, long fiber, axially aligned in the mold,” Joe explains. “We also realized that it just won’t break when we electronically protect it. This is what you learn and can say with confidence after seven years of development.”
Tilting the motor up and down from the operator’s seated position by pulling or pushing on the long aluminum tiller was a bit trickier to solve. Grez tweaked the mechanics to reduce the force needed for this process and did away with the up-detent, so the motor can slide forward 4” to 5” (102mm to 127mm) after tilting as the operator continues to pull on the tiller arm.
This solution also reduces motor protrusion, a practical consideration at crowded dinghy docks. To lower the motor, a push on the tiller suffices. The ball-shaped throttle at the forward end of the tiller turns right for forward and left for reverse with a safety key that, when pulled, shuts down the motor.
“There’s no other motor that’s designed for the actual user experience in a dinghy,” Linda says. “One of our early testers took it out for a weekend, and we asked, ‘What do you think about it?’ And he said: ‘My wife loves it. She doesn’t mind handing it up to me or taking it off the transom.’ We didn’t realize that it was going to be so much more attractive to women.”
The Consumer Product Approach
A stroll through the workshop adjacent to the Grezes’ home provides insight into their systematic approach based on their development of consumer products, which are beaten, bent, and broken so potential issues are identified and sorted out before starting large-scale production. To check functionality and power, Joe tests each unit in a round basin equipped with a thrust sensor.
In the backyard, the hood of a 1956 Series 1 Land Rover (a restoration project awaiting its turn) serves as the stage for testing UV resistance of the plastic parts in the motor cowling and the lower unit. In Joe’s opinion, “A lot of marine products are designed, built, and launched without full appreciation for use cases and marine challenges. So there’s a nonending list of problems with most boats resulting from components produced without a deep level of background testing and evaluation-improvement cycles.”
They learned important lessons from their first product, the Electric Paddle, that small kayak motor they introduced in 2010.
“We are not young techies [but] gray-haired lifelong sailors and have been creating innovations for brands like Philips Sonicare for decades,” Joe says. “We put over 120 test units in the field for five years and conducted literally thousands of hours of testing ourselves, even sponsored solar race teams to find extreme-service issues before even designing our EP Carry, and we talked to thousands of potential customers about what they wanted.”
Feedback from testing and their own relevant experience informed early decisions like material combinations that resist corrosion. He chose 316 stainless steel after finding out that customers didn’t appreciate bronze. Regarding screw size, spacing, and materials in the bracket, a combination of 5 Series aluminum and stainless steel “seems to be working pretty well,” according to Grez.
To resist damage from exposure to the elements, the motor carriages are made of a gray polycarbonate ABS blended with a UV-inhibiting additive. Other components that had to be tested for reliability, robustness, and water resistance include the electronic circuitry, driveshafts, motor shaft seals and couplings, water-lubricated gear cases, and electronic shear pins.
Within the first three months after launching, a head-connection issue related to the use of the wrong screws had to be addressed. The offending parts were modified to solve the problem. As mentioned, Grez altered the tilt mechanism and also updated the firmware to eliminate the need for throttle calibration. “Otherwise, it’s all the same product and parts. With a large number of units in the field, problems remain minimal. Warranty calls are at normal levels for the high-quality consumer-product category.”
To some extent this story is a sequel to the Grezes’ previous careers at Sonicare, before the company was bought by Philips in 2000. Twenty years on, they can still fall back on a network of engineers and other subject matter experts in their immediate geographical area. “We had a broad team of experienced manufacturing reps who helped us initially to get parts spec’d out, working with different vendors, and fine-tuning these parts, so they were not only manufacturable but also made well,” Linda explains.
As the project manager at Sonicare, Joe had many engineer contacts with relevant skills and expertise, which came in handy for his new venture, too. As a CAD user, he designed the outboard’s parts before a mechanical engineer made them for production, i.e., by checking for consistent wall thicknesses. “They knew me, so they were willing to come on board part time,” Joe says. “It was like a barn raising when we launched it. Everybody came. We had 12 people helping out.”
Addressing Range Anxiety
As mentioned above, the key question every manufacturer of electric propulsion systems must address is the worry about range and runtime based on available battery capacity. “We try very hard to make sure people’s expectations are reasonable, so we ask, ‘How far out do you anchor? How many trips per day do you do?'” Grez explains. He also points to a tool on the website, a calculator for estimating speed and range for popular dinghies with the EP Carry. “If you go ship to shore five times a day with your dog [and cover] less than three miles, you’ve got plenty of charge to go full throttle each trip. Or if you back off to half throttle, you get five or six miles.
The EP Carry is powered with a stock 24V waterproof LiFePo4 battery (# K2B24V10EB) from K2 Energy, which weighs 6.4 lbs (2.9 kg), and the corresponding charger (# K2C24V2A). For more runtime, customers can order a larger 22-Ah battery weighing 12.5 lbs (5.7 kg) or rig their own 24V or 48V batteries, as long as they properly connect to the EP Carry’s power cord.
Earlier in the product cycle with the lower powered Electric Paddle, PropEle used NiMH batteries, which provided about two hours of runtime at full throttle but weighed a couple of pounds more. I asked Grez if he considered building his own battery as other vendors of electric boat motors do. “With lithium [technology] it is pretty easy to become a pack producer nowadays. You can buy BMS boards and cells and put them together. But for now [we keep buying them from experts]. There’s some functionality I want to put in that is not in stock battery packs, but the point is it is enough work to design something that is this awesome in a motor without focusing on the battery pack as well.”
Participating in the Salish 100, a raid that takes contestants on a 100-mile course along the entire Puget Sound, from Olympia to Port Townsend, Washington, Grez trotted out Swe’ Pea, a converted Jet-14 Class sailing dinghy (a classic Uffa Fox design from 1950 based on the International 14) with a dry weight of about 300 lbs (136.1 kg). The exercise was to prove he could go 100 miles in six days (about 16.7 miles/day) without plugging in.
He fitted Swe’ Pea with two AllPowers 100-watt 18V 100-watt 18V solar panels wired in series on top of a bimini, plus a $50 GreeSonic MPPT Solar Charge Controller 15-amp 12V/ 24V and a $45 Battery Coulometer TK15, which helped monitor the battery’s state of charge and charge/discharge rate. His secret weapon, though, was his own solar calculator that computed the watts generated by his solar panels at a particular latitude, time of year, and speed at various levels of input power, which then are used to determine the boat’s range.
The solar question “How far can I go?” invites another question, Grez says: “How fast and under what condition? And the correct answer is: You run as long as there is sun.” A slide of his Power Point presentation reminds his audience: “You still mind the tides. You still watch the weather. But instead of wind, you use the sun.”
Here are the performance parameters Grez recorded in those six mostly overcast days, with 30% sunshine: Maximum speed, 5.5 knots (with a push current of 1.5 kts.); minimum full-power speed, 1.7 knots over ground, against chop, tide, and 20+-knot winds. But the key numbers are these three: 120 nautical miles total distance traveled in 40 hours at an average speed of 3.1 knots.
On Grez’s power-input curve this speed of 3.1 knots corresponds to roughly 100 watts. He used about 4 kWh of energy (watts x hours) to go 120 miles. According to the gasoline gallon equivalent (GGE), one U.S. gallon of gasoline contains the equivalent of 33.41 kWh of electricity. Therefore, Grez burned the equivalent of 0.119 gal of gasoline (4 kW/33.41 kWh/gal) for those 120 miles, which means that Swe’ Pea, in theory at least, could have covered 1,008 nautical miles on the equivalent of approximately 1 gal of gas. More technical details and daily log entries of the Salish Sea 100 adventure can be found on the EP Carry website.
Discounting complex calculations of the true social and environmental costs of propulsion technologies, a common challenge for boat owners who consider switching to e-power is the delicate balance of range, speed, battery, and charging capacity. Allies in this quest are designers who conceive lighter, more efficient craft that help boost range and performance for electric power. We featured examples such as the Seabubbles water taxi and the Candela foiling runabout (see “From Niche to Market,” PBB No. 173) or the all-carbon 50-knot SAY 29 (see “a = F/m,” PBB No. 180). But these were much larger craft custom designed around the propulsion system. So how can Grez, as a provider of propulsion systems, address or influence the development of a platform that helps maximize performance and range of his 220-watt electric outboard?
His answer is simple and goes out to designers: Extend the waterline. “For our speed calculator I use a hull-length multiplier of 0.6 to calculate the hull speed of an inflatable, because the waterline doesn’t start until 1’ [0.3m] abaft of the bow, and it ends about 1.5’ [0.46m] in front of the stern where the two [inflatable] tubes stick out. So the [de facto] hull speed of a 10’ [3.1m] inflatable is [almost] the same as that of a 7-footer [2.1m].
“Moving the transom out would work a whole lot better with electric motors. I’ve done the math. If you lengthen the hull, [inflatables] are not bad. The fact that they are shaped like a sponge does not make a big difference; it’s the effective waterline length. You would gain the sizable portion of one knot.”
But dinghies are not the only craft for the EP Carry, which is now also powering fishing kayaks and catamarans marketed by an OEM, Jackson Kayak in Sparta, Tennessee. Rebranded as Flex Drive E, the EP Carry motorhead easily switches out with the kayak’s pedal propulsion system. “The head of the pedal unit in front of the seat comes off, so our motor replaces that,” explains Grez. “They have a lifting and lowering skeg with a propeller on it. We did a 6-to-8-month development phase with them and started production a couple of months ago.”
A day after visiting the manufacturing site of the EP Carry, I asked Russell Brown of Port Townsend Watercraft to go for a spin on a PT 11 nesting dinghy, which he offers as a kit. Handicapped by a cast on his left thumb, Brown needed assistance in clamping the EP Carry on the stern, connecting the battery that lives in a storage bag, and splashing the boat from the dinghy dock of Port Townsend’s Point Hudson marina. But on the water, even with this handicap, he was firmly in command of the boat and in control of the EP Carry as we puttered along and circled the schooner Martha, out with a gaggle of high school students, before heading north to Point Wilson.
Brown said he does not sell the motor, nor does he plan to. But “we tested it before, and it is the only motor we recommend for use, because it fits our philosophy.” Quietly and dutifully the little motor pushed this elegant plywood dinghy along with its payload of two 6‘ (182.8cm) adults. Switching operators, I needed a moment to get the hang of the throttle arrangement but quickly found a comfort zone.
With single occupancy, the PT 11 (11‘/3.35m LOA, 90 lbs/40.8 kg) reached a GPS-checked top speed of 4 knots in slack water, and even after one hour of goosing the boat around at or near full throttle, Brown’s shiny carbon oars remained shipped, because there still was plenty of juice in the battery.
Approaching the dock in slow motion I sought a tiny thrust of reverse for an extra-elegant docking but turned the throttle right when I should have turned left. The hull hit the dock with a gentle bump. Embarrassed by this miscue, I also forgot to yank the safety key to shut down the motor and disable the throttle. But no harm, and 10 minutes later after they were rinsed off, the nesting dinghy and the EP Carry were back in the camper shell of Brown’s truck, ready for the ride back to the shop.
In pushing a small dinghy around with one or two adults at up to 4 knots under full throttle, the EP Carry did exactly what the folks at PropEle predicted: It aided the commute from shore to ship and back, replacing noise, smoke, odor, and the fuss over filling a gas tank with calm, smokeless, and odorless convenience.
In this context, range or speed anxiety won’t be an issue for most users. The fact that this 14-lb motor can easily be mounted and removed without backbreaking contortions and is 100% operable while the driver remains seated safely in the boat or on the tubes are helpful arguments for an aging boating demographic to consider clamping this little electric eggbeater on their tender’s stern.
Beyond that, the EP Carry is an example of a structured and rigorous development approach as it is practiced in the consumer product industry. With that in mind, Joe and Linda Grez have deliberately flown below the radar during the test phase while building a feedback loop from test customers to ready the EP Carry market before rolling out the motor.
The next step is growing the business to serve new customers and larger markets, something Tesla chief executive Elon Musk referred to as “production hell.” This is, as Joe pointed out succinctly, not just a matter of getting people to sign orders but bringing investors on board to help finance the increasing demands on supply chain and manufacturing capacities.
If successful, North Bend, Washington, might someday rival Gilching, Germany, as the capital of small electric outboards.
Dieter Loibner is editor-at-large of Professional BoatBuilder.
Runtime and Range
Most dinghies will achieve maximum speeds of 3.3 to 4.5 knots. Typical ship-to-shore use results in two to three days of runtime without the need to recharge.
- Full throttle—1 hour = 3.3 to 4.5 nm
- Half throttle—2 hours = 5 to 7 nm
- Slow speed—3 to 7 hours = 7 to 11 nm
Output Speeds with Payload on Some Popular Boats
- 10’ (3.1m) Walker Bay, 450-lb (204-kg) payload, 3.6 kts
- 9’ (2.7m) Inflatable Riken, 250-lb (113-kg) payload, 3.4 kts
- 12’ (3.7m) Gig Harbor Pt Defiance, 520-lb (235-kg) payload, 3.9 kts
- 8.5’ (2.6m) Porta-Bote, 250-lb payload, 3.4 kts
- 16’ (4.9m) Wenonah canoe, 300-lb (136-kg) payload, 4.7 kts