Isabella, Mariner 31 Powered by Electroprop Mariner Serial Hybrid with 4 KW Diesel Generator




I purchased Isabella in 1999 and, for the next three years, enjoyed sailing on the Chesapeake Bay with her. In 2002, I hauled her out of the water and began what I intended to be a modest upgrade, which I hoped might take a year or so. Built in 1971, my Mariner 31 Ketch needed a bit of attention.

Predictably, the modest upgrade turned into a complete restoration. Over the course of the next nine years, I pulled every wire, every bit of plumbing, every system that wasn’t fiber-glassed to the hull. The house electrical system went from five circuits to fifteen; every incandescent bulb was switched to LED; I installed a freezer; installed an inverter; installed a Force 10 propane heater; installed beautiful bronze ports all around; and brought all the bright work up to the highest standard.

When nearly all the ancillary systems were completed, I began wrestling with the question of what sort of propulsion system I wanted aboard. Having removed a 450 lb. Perkins 4107 from the engine compartment, the thought of more or less permanently mounting another diesel monstrosity in the engine compartment had no appeal.

So I did my homework. I spent over a year on the web, talking with marine engineers and builders. Many wanted to stay within their own zone of familiarity and were uncomfortable talking about “alternative technology.” Some were excited about vanguard technologies but clearly had not thought through the challenges or done the actual research necessary to make it successful.


“Simple, elegant, and fully adequate… smooth, quiet, pollution-free and, yes, she is beautiful.”




What I knew I wanted was the following:

  1. A component system, with no component weighing more than 125 pounds. That way, as the technology advanced, I could switch out components with relative ease.
  2. A 48 volt propulsion drive and a 12 volt house system.
  3. Odyssey batteries.
  4. The largest solar panel I could safely mount.
  5. A 48 volt wind generator.
  6. A diesel generator, capable of charging the 48 volt system.

I spoke over the phone with a number of “alternative technology” companies. Finally, after about five minutes of talking with James Lambden, I knew I had found the guy I would be working with. He was committed to the technology, of course; but more importantly, he had done painstaking years of research, and developed a propulsion system that was simple, elegant, and fully adequate to the needs of sailors. Beyond this, he was always willing to talk me through my own misunderstandings, and patiently guide me to the solution I needed to find.

The system I have aboard Isabella now could probably sail around the world without refueling, if the sun and the wind hold up. Here are some of the specifics:

  1. An Electroprop 5.5 kW drive. It is unbelievably smooth and worry-free. It generates plenty of thrust for Isabella, who weighs in at 11,000 lbs.
  2. A new propeller with much greater surface area and pitch than the previous one.
  3. A Sanyo 205 watt solar panel, mounted on the transom rail. It feeds the house battery system and, on a sunny day, provides all that I need.
  4. An Air Marine 48 volt wind generator, mounted on the mizzen mast. Over 400 watts on a windy day. This feeds the 48 volt propulsion system.
  5. Four Odyssey PC-1800 batteries, configured to 48 volts.
  6. Two Lifeline M-31 batteries, for the house system.
  7. Three charge-controllers, whose use I will describe below.
  8. An  ElCon charger, for charging the 48 volt system from shore power.
  9. A Farymann 18W water-cooled diesel generator, capable of producing roughly 4 kW of power, at 3300 rpm. This is a prototype that I began building, but could not have completed without James. I chose the Farymann engine because it is the world’s smallest water-cooled, fixed-speed, diesel engine. I had a custom bracket built for the belt drive system I needed. James did the invaluable work of figuring out how to translate mechanical into electrical energy.

Custom 5 KW Serial Hybrid Electric Drive with Stainless Steel Drop Pan Mount, Permanent Magnet, Dual Stator Motor, and Helical Gearbox, with Ferryman Diesel Electroprop Generator



As you can probably figure out, I wanted as much redundancy in the system as possible. There are three ways to charge the 12 volt house system: shore power; the solar panel, and by relying on one of the charge-controllers to drop voltage down from the 48 volt propulsion system to 12 volts for the house loads. There are also three ways to charge the 48 volt propulsion system: shore power; the Farymann generator (which uses the second charge-controller); and the 48 volt wind generator.


“It is a joy to be aboard.”

I don’t know if Isabella is the most sophisticated modest-sized sailboat on the Chesapeake Bay, but I would not be surprised to learn that she is right up there with the best of them. The propulsion system that James put together is smooth, quiet, pollution-free and, yes, it is beautiful.  I sail with the propulsion system on at a low level and always add a knot or so of speed without using up too much power. It is a joy to be aboard.

I cannot recommend James highly enough. Without fanfare, he is on the cutting edge of the twenty-first-century technology that will come to dominate the marine world. If you want to talk with me further, please send me a note. I can be reached at

Joshua Mitchell
Owner: Isabella (Oxford, MD)
August 2012