Diesel Outboards: A Growing Trend

With the growth in popularity of larger outboard boats over the last decade and the increased horsepower needed to push them, it was only a matter of time that diesel outboards started to find their way into this rapidly expanding market.

Leading Competitors in the Diesel Outboard Market

Two main competitors exist in the offshore diesel outboard market today: Oxe Marine, which offers 150 to 300 hp models, and Cox Marine diesels, with their 300 hp engine and higher hp versions in development.

Pros and Cons of Diesel Outboards

Of course, there are pros and cons with anything and with the diesels, the negatives seem to be the weight and the price issues. The diesel outboards weigh approximately 250 to 300 pounds more than their gasoline competitors and carry a price tag of around 30 percent higher than the gas motors.

Advantages of Diesel Outboards

The positives of the diesels include fuel economy, range, longevity, longer service intervals, safety (less flammable, especially when carrying extra fuel) and more torque. The commercial rated Cox 300 diesel makes over 500 lb of torque. It produces 30 percent less CO2 than a gas outboard and is generally 30 percent more fuel efficient. It also has a 250 hour service interval for extended run time between oil changes.

With gasoline engines, there’s always been an issue with the fuel burn remaining high at trolling or slower speeds, but with the diesel engines the fuel burn drops way down during the long hours spent on the troll.

Real-World Performance: A Case Study

John Bowen of Texas Diesel Outboard in Kemah, Texas, has been running the Cox 300s on his 36-foot Invincible for the past couple of years after doing a year of data collection with the original Yamahas that came with the boat. , “Changing to diesel outboards on our center console has greatly increased the range due to the improved fuel economy,” John says about the performance after the swap. “Saving money at the fuel dock is a bonus as well. The torque is phenomenal, getting the boat on  plane quickly even when tournament loaded. The torque also allows much more vessel control for low-speed maneuvering.” He also states that swinging bigger props, turning slower rpm really cleans up the wheel wash as well. He attributes this in helping him with his success in tournaments this past couple of seasons. When I visited his shop a while back, he had an outboard that he was rigging with the diesel outboards as a yacht tender, which seemed like a great idea because they wouldn’t need to carry gasoline on the diesel-powered yacht just for the tender/fishing boat.

The Future of Diesel Outboards

The only thing for sure is that things will change and I’m sure that we will be seeing more of these engines on outboard transoms in the near future.