Rhumb Lines: The Diesel Engine Dilemma


As the threat of global warming is forcing policy makers around the world to explore ways to wean their economies off carbon based energy sources, it is only natural that a sailor might want to reassess their auxiliary engines. The rising popularity of electric propulsion and recently adopted industry standards for the higher voltage systems required for these electric motors provide further enticement for ditching ye ol’ diesel.

Every reduction in CO2 emissions counts, as they say, but I imagine the amount of CO2 emitted by sailors each year is barely a drop, in a drop, in a drop in the bucket. Sure, there are other negative side effects to having an auxiliary engine (typically diesel). Lubricating oil, unburned fuel, and spillover at pumps eventually finds its way into the water. Then there is the noise and smell.

But when I consider the impacts of mining and fabrication associated with electric propulsion, I wonder if the estimated $20,000 and 50-hours spent replacing my Universal diesel with a state of the art electric propulsion system and lithium ion batteries would be better spent working to change government policies that are inhibiting the growth of solar power in my home state of Florida.

Maybe a simple switch to plant-based diesel would achieve the same net benefit for the environment? How much will I actually be running my engine, anyway? These are the questions I plan to examine as I contemplate repowering my recently acquired S&S designed 1971 Yankee 30, Opal. The stout little sloop is in dire need of some love and will be the basis of a series of articles highlighting the variety of products, tools, and skills associated with a major refit— from masthead sheaves to prop nut (see page 23). Many of these articles already exist in our archives, many need updating, and some have not yet been written.

Our last big report on electric propulsion (see PS September 2008, “Electric Propulsion for Sailboats”) pre-dates the newer standards established by the American Boat and Yacht Council, which opened the door to a range of electric and hybrid-electric systems now entering the market. Late last year, the ABYC posted a round-table discussion on electric propulsion, and the variety of options was astounding (www.youtube. com/watch?v=7ibuqEvQcZ4).

Opal’s diesel is a bit of a mystery. Based on the incomplete logbook and the now stalled hour meter, it appears to be a remanufactured late 1970s Universal 5411 diesel installed sometime in the 1990s. I bought the boat assuming a repower or rebuild was in the future, but so far, the engine, which is essentially a marinized Kubota Z500 tractor engine, checks out pretty well. One of its saving graces may be the freshwater cooling system, delivered by a lovely cast silicon-bronze Oberdorfer pump and a 50-year old copper-nickel Sen-Dure heat exchanger that now gleam like an 18th century chronometer.

Except for a leak at the waterpump weep hole and associated corrosion beneath, I’ve found no obvious faults. An oil analysis and injector service is in the works, and the more I look at this marvel of machinery, the more impressed I am. The fact that it’s still chugging at least 40 years from the last year of production (1982) says a lot about the endurance of these old tractor engines.

Now, if I can just do something about the noise, I might just abandon my electric dreams altogether.

Darrell Nicholson
Darrell Nicholson is Director of Belvoir Media Group's marine division and the editor of Practical Sailor. A lifelong thalassophile, he grew up sailing everything from El Toro dinghies to classic Morgans on Miami's Biscayne Bay. In the early 90s, he left a newspaper job to sail an old gaff-rigged ketch across the Pacific and has been writing about boats and the sea ever since. His weekly blog Inside Practical Sailor offers an inside look at current research and gear tests at Practical Sailor, while his award-winning column,"Rhumb Lines," tracks boating trends and reflects upon the sailing life. He sails a Sparkman & Stephens-designed Yankee 30 out of St. Petersburg, Florida.


  1. Although I don’t own an electric motor for my Catalina 25, I do own two Teslas, run my home on solar, and remain committed to reducing my carbon footprint. When statements like “I consider the impacts of mining and fabrication associated with electric propulsion” demonstrate a lack of knowledge on the production of electric propulsion. Diesel fuel does not rain from the sky and find itself magically in a sailors fuel tank. I totally agree that sailors contribute to a very small amount of the pollution but consider what you have onboard your vessel. The greatest threat to your vessel is fire and the reason for fire is electrical, engine and fuel.(https://www.boatus.com/expert-advice/expert-advice-archive/2021/february/analyzing-onboard-fire-claims)

    WAIT! ELECTRICAL! read the Boat USA article. The fact of the matter is that if lithium touches water it goes boom, so they have no business being on a boat, right, well no. Tesla can drive in deep standing water. Manufacturers make their batters like Ft. Knox. They’re tight, and a heck of a lot tighter than a fuel tank. Internal Combustion Engines,(ICE) experience a ton more fires than electric cars. Electric propulsion systems are designed with very safe parameters and are far safer than ICE systems.

    Electric systems can create their own energy through regeneration as you sail. Electric can be powered by solar. Electric will make you a better sailor, because you’ll rely more on the wind than on fossil fuels.

    Look I know diesel engines have the endurance and range, and I also know that switching is a gutsy move for a multitude of reasons, but electric propulsion whether in a car or a boat is just simply a different way of thinking. I leave my home with a full battery and at a quarter of the cost of regular gas. My maintenance is practically nothing. I’m not running my car via a series of small controlled explosions. When I’m not accelerating I’m charging my batteries. My car’s motors are rated at a million miles and my batteries will go 300k-500k miles. My cars are much safer than my previous ICE vehicles. All of this applies to a sailboat. So when my new 9.9 outboard starts to get tired, yeah I am going electric propulsion. When I buy my 35 to 45 foot sailboat, that will be electric too. Once you go electric you won’t go back.

    • When your still-to-be electric boat motor has run as long as as well as the described diesel engine, I’ll take a second look if I have the money and the belief. Untill then I will stay with my own less travelled version, possibly switching to modern veggie fuel as it develops and becomes available, thus furthering my contribution to a smaller drop.

  2. The real problem in the marine C02 question is the huge behemoths that tra sport goods around the world. They account for 15% of the worlds greenhouse gases. Their cousins the fishing trawlers account for 50% of the oceans plastic pollution. It’s not drinking straws at all. Both are flagged with bubble gum republics that care less. They just want the money. One of the top 3 doesn’t even have coastal waters.vbeyond 200 miles off shore they do as they please and have been noted to drown onboard government inspectors who dare make them comply.
    The answer stop buying from lands 4000 miles away. Shop at home. Build at home.

  3. I have a Kubota-based Universal M35B in my Luders 33. Installed it myself in 2001. It has run only on B100 or B99 diesel fuel since new. The only associated problems have been a bit of paint lifting on the engine in places where fuel was spilled and some rubber fuel lines original to the boat had to be replaced due to softening. The newer fuel lines seem to hold up well. I burn about one tank of fuel (35 gal) per year. The contribution of my diesel to global warming is less than a drop in a drop in a drop. It may even be carbon negative, as most of the oil comes from restaurant deep fryers, or close to carbon neutral when it comes from soybeans.