Why Use A Trailer When Your Boat Could Have Wheels?

Recently, I found myself standing at a campsite in a place called Wilsons Promontory (it’s actually a peninsula). I heard a dull rumble, a thrumming of engines, and turned to see an almighty sight. A large boat, flanked by a small cadre of spotters, was driving down the road?! And there were two more behind it!

I’d never seen anything like this in my life. An amphibious boat with wheels that could self-launch on the beach! I quickly puzzled out that this craft had a hydraulic system for raising and lowering its wheels. This allowed the wheels to be deployed for entering and exiting the water and raised to reduce drag when at sea. Genius!

I surmised that this technology was too cool and too useful to be a one-off build, and I was right. Once I got home, I dived into the research and got my answer. What I was looking at was a boat equipped with “Sealegs,” a unique amphibious technology straight out of New Zealand.

On Land, On Sea

As the company tells it, the concept for Sealegs started as a napkin sketch in 2001 and eventually became a production reality in 2004. Since then, the company has expanded to offer a range of amphibious watercraft equipped with wheels. Sealegs also sells its amphibious drive systems such that they can be integrated to designs from other manufacturers.

Throw the Sealegs gear on a boat, and you have an amphibious platform that can be operated with a minimum of supporting infrastructure. There’s no need for boat ramps, jetties, or other structures. The boat can simply deploy its wheels and drive on to land—and vice versa. This also makes launching the boat far easier and more practical, reducing the number of crew to do so safely.

The basic concept is simple. The boats are fitted with three wheels—two at the back, one at the front. These wheels are mounted on hydraulic rams so they can be extended and retracted as desired. Each wheel is fitted with a hydraulic motor, giving the craft all-wheel drive. If you haven’t heard of a hydraulic motor, it’s quite simple. It’s a motor that turns when you pump it full of hydraulic fluid under pressure.

Of course, to run the motors, you need a source of hydraulic pressure. This is typically achieved with a small auxiliary engine running a hydraulic pump. The engine can be set up to run off the same fuel tank that supplies the boat’s sea engines. If you have a smaller boat equipped with, say, Sealegs System 70 setup, it comes with a 35 hp Briggs & Stratton petrol engine. If you have a larger craft, you might be running the Sealegs System 100 setup with a larger 97 hp Kubota diesel.

Depending on the exact setup chosen, it’s possible for a duly equipped craft to achieve speeds of up to 7 mph on land. Maximum torque is as high as 7,744 foot-pounds with a System 100 setup; it’s enough to climb up to a 15-degree grade in the right configuration. The largest Sealegs setup is suitable for vessels with a gross weight of up to 16,000 lbs.

Alternatively, Sealegs has also developed an electric system, too, for its small Electric E4 craft. This replaces the hydraulic wheel motors with brushless electric hub motors good for up to 6 mph. They’re paired with a 7 kWh lithium-ion battery, with a total run time of 1.5 hours. That’s enough for up to 20 launch and retrieve operations on a single charge, or around 1.5 hours of driving around on land.

Sealegs has sold amphibious vessels to users all over the world. They’re particularly popular with first responders, who get great utility out of the self-launching capability.

Down At The Prom

The boats I saw down at Wilsons Prom are some of the biggest vessels equipped with Sealegs gear. They were designed and built specifically for tourism operator Pennicott Wilderness Journeys by Sealegs, Naiad Design, and Naiad’s Australian builder, Kirby Marine. The resulting craft – the Naiad 11.5 m Tourist Sealegs – carries 30 passengers plus two crew. Each boat is equipped with twin Yamaha 350-horsepower outboards for propulsion on the water. The boats can easily reach 38 knots with the engines at half-load, with typical cruise speed stated as 25 knots.

Despite their size, the craft will do 5.6 mph on land. That’s more than enough for launch and recovery operations and getting the boats off the beach. Indeed, as I saw during my stay on the Prom, the boats are driven quite a ways off the beach, through the campsite, and to a dedicated parking area of their own.

A tender was put out to multiple boat operators to run the tourist boating operation at Wilsons Prom, and Pennicott came out ahead thanks to the Sealegs technology. The ability of the boats to self-launch and recover meant that the wilderness region could remain unspoiled. There was no need to build a jetty, dock, or ramp that would otherwise clutter the pristine coastline.

These boats are very cool. They look totally badass when they’re crawling on land, and they’re pretty swift on water, too. If I ever get a boat, I’ll dearly want it to have the cool wheels so I could just drive it in and out of the water at will. If you’ve experienced the hell of launching and recovering a boat by yourself, you’ll know exactly what I’m talking about.

Image credits: Lewin Day, Sealegs, PennicottJourneys via YouTube screenshot