Hushcraft Thrust Pilot Pod Drive

Hushcraft is testing out its full hybrid diesel-electric conversion system on Eva May, a revamped 1979 Princess 41. Is this new technology up to speed, or just a big waste of energy?

Hybrid boats are nothing new, with serial hybrids – the most common kind, combining a diesel engine and an electric motor – readily available from producers such as Greenline. Alternatively, parallel hybrids keep the motor and engine relatively separate but driving through the same shafts and propellers in a way similar to most modern hybrid cars.

However, an alternative hybrid boat is fast emerging. Hybrid diesel and electric propulsion systems on boats can be entirely separate, as demonstrated by Hushcraft on its latest craft, Eva May.

An old but thoroughly rejuvenated Princess 41 dating from 1979, Eva May has retained its diesel engines as well as all its conventional steering and stern gear. But with the addition of what Hushcraft calls a Thrust Pilot pod, Eva May became a hybrid in December last year.

We get to know the newest tech on the seas…

  • Hushcraft’s Thrust Pilot pod comprises a small modular bathing platform which contains a single 15kW (output) water-cooled electric motor connected to a steerable-saildrive leg
  • This provides separate electric propulsion that is independent of the diesel engine drivetrain
  • According to Hushcraft’s MD Ben Simpson, the electric motor provides a 6-knot top speed
  • Under diesel power alone, Eva May can achieve 18 knots
  • The Kräutler electric engines that Hushcraft use range from 2.5kW to 30kW (3.4hp to 40hp)
  • They sport a boost function that allows for a 30% performance increase for up to two minutes
  • On a twin installation, that could provide up to 104hp in short bursts, and a constant 80hp underway

Eva May’s particular set-up represents only one of Hushcraft’s innumerable mix-and-match options.

  • Air-cooled and water-cooled versions are available, although everything 20kW or above is water-cooled
  • The drive can be fixed, but mechanical steering gives up to +/-45° of articulation, while electric drive gives +/-90°
  • Eva May has mechanical steering that is linked to the same steering wheels that connected to the conventional rudders
  • It features a 100% redundancy back-up of propulsion and steering
  • The electric drive can be used as a stern-thruster
  • Like a lot of electric or hybrid aficionados, Hushcraft claims ‘silent cruising’

Is fuel consumption significantly reduced?

  • Potential generator useage aside, electric propulsion has no emissions at point of use so is environmentally beneficial
  • Claimed potential fuel savings will depend on your typical useage
  • If you use the electric drive to travel along at low speed, you’re effectively dragging one or two small sea anchors through the water in the form of the diesel engine’s temporarily redundant propellers and sterngear
  • A generator is required to keep your battery topped up
  • However, shorepower in marinas is nowadays generally included in the price of the mooring
  • If much of your boating is done at planing speeds, anecdotal evidence suggests that we spend considerable more time at low speed than we realise

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Please note this content is adapted from an article appearing in Motor Boat and Yachting Magazine, April 2017