Like most nautical principles, it’s better to learn about them when you can rather than when you must. The same applies to boat fuel. What’s the proper choice for your boat and what are the implications of that choice?
This knowledge is not only useful for current boat owners but also for first-time buyers thinking about purchasing a boat of their own.
As a first-time boat buyer, you may be wondering: What are the implications of a diesel vs gas-powered boat engine–or an outboard vs. an inboard boat engine? How do the fuel requirements differ between new boats and used boats?
So, read on, and you’ll be able to check off the basics of boat fueling from your list of needed boating knowledge.
Understanding Boat Types, Fuel Requirements, and Potential Risks
Navigating the world of boat fuel choices doesn’t have to be confusing.
There are boat engines, like pleasure boat engines, that can run on either gasoline or diesel fuel. Gasoline engines are far more common in pleasure craft than diesel ones.
If you’re unsure what fuel to use, refer to your engine manufacturer’s fuel and oil specifications.
Diesel boats run on the same fuel used in diesel cars (called #2 diesel fuel). Gas boats run on fundamentally the same gas that gas cars do, but there are a few details about what type of gas not to use in your gas boat that are worth understanding.
Diesel Fuel
Diesel fuel is an excellent choice (and, as the boat’s weight approaches 18,000 pounds, the only choice) for larger boats. Diesel-powered boats provide increased torque and horsepower compared to gasoline engines of about the same physical dimensions. Diesels are also somewhat more fuel-efficient than gas-powered engines.
Claims that the cost of owning a vessel with a diesel-powered engine is less than a comparable gas engine with comparable usage are, at best, dubious. A diesel-powered engine will raise the price of a new boat significantly.
In used boats, the costs to replace diesel engines are 2 – 6 times higher than those of comparable gas engines. Also, diesel engines are notoriously more finicky than gassers about what they ingest: air, fuel, coolants, and lubricants. That’s worrisome when you consider that diesel repair costs are enormously higher than those for gas engines.
It would take decades to recoup the much higher initial and longer-term diesel costs via savings on fuel. If your boat’s size dictates that you need a diesel-powered engine and you can afford one, then get one. But if you can get away with using gas, you’ll probably come out ahead in total cost of ownership. (For more on this and many more worthwhile insights, see Mid Size Power Boats, by David H. Pascoe, © 2003, David H Pascoe).
Gasoline (According to % of Ethanol)
Gasoline types are categorized according to the percent by volume of the chemical ethanol mixed into the formulation. Those designations are E10 and E15, which indicate that the gasoline is a blend with ethanol levels of up to 10% and 15%, respectively.
While these fuels might help reduce pollution, they may also cause corrosion and damage to inboard gasoline engines, such as clogged fuel lines and fuel filters. Damage to fiberglass fuel tanks may also occur over time.
A modern boat’s fuel system is designed to deal with E10 fuel. Owners of boats older than 15 years should choose ethanol-free fuel (E0) whenever possible and be alert for possible engine damage and the beginnings of slow leaks in fiberglass fuel tanks–if E10 fuel is used. E15 should not be used for marine applications.
Experienced boat owners usually prefer 0% ethanol (“E0”) in their fuel regardless of their boat’s age. It’s usually available only at busier marinas and service stations near lakes and rivers popular with boaters.
If E0 is not available, E10 fuel is acceptable.
Most marine engine manufacturers, as well as the Environmental Protection Agency (EPA), do not recommend using E15 in boat engines due to the potential for severe damage to fuel system components.
2-stroke Outboard Engines and Mixing Oil with the Fuel
Most outboard motors, until just a few years ago, used a 2-stroke gasoline engine design. Two-stroke engines complete a power cycle in just two strokes (1 up and 1 down) of a piston.
Four-stroke engines, employed by virtually all modern passenger automobiles, complete a power cycle using four strokes (1 up, 1 down, 1 more up, and 1 more down).
Two-stroke outboard motors usually require oil to be mixed in with the fuel. The oil is used to lubricate moving parts of the engine.
When mixing oil into boat gasoline, a special oil is required. You’ll also need to achieve the proper oil-to-gas ratio Most modern 2-stroke outboards have an oil reservoir and pump system that automatically supplies the required oil and gas mixtures to the engines. Just make sure the oil reservoir is adequately filled with the proper oil.
Engine damage can result if the fuel going into the engine is not mixed in according to the recommended ratio.
Fueling Tips for Boaters: Safety and Efficiency
Safety practices, especially with gas engines, are crucial when you fuel your boat. For a more detailed discussion, see this excellent article.
Photo source: © City of Mentor, Ohio
Above: This pump supplies diesel or gasoline. Arrive at the fueling station knowing exactly which fuel your vessel needs, and always double-check that you’re pumping the correct type during the fueling process.
Safe Fueling Practices
For safe fueling, it is advisable to follow these basic guidelines:
- Extinguish all open flames and turn off all electronic devices. Turn the bilge blowers off.
- Have passengers exit the boat while fueling.
- Know about how much more fuel your fuel tank can hold.
- Ensure you know what fuel you’re pumping (gas or diesel) and where you are pumping it. Make sure it’s the fuel fill and not the water tank, waste tank, or (heaven forbid) a rod holder. Note: It’s been done, leaving lots of flammable gas on the deck.
- Prevent overfilling and especially watch for overflow from the fuel tank vent system. Clean up any spills before departing.
- After fueling is complete, RUN THE BILGE BLOWERS FOR AT LEAST 4 MINUTES. Then, perform a sniff test around the fuel tank area.
- Start the engine(s) before guests reboard.
- Keep the bilge blowers on until you leave the no-wake zone (and any time you’re at idle speed).
By following these safe fueling practices, you can protect both your engine and yourself from potential hazards
Maximizing Fuel Efficiency
The boat captain has a great deal of influence over their vessel’s fuel efficiency.
Did you know that your boat uses less fuel on plane than it does when you are cruising at less than planing speed?
So, to improve fuel efficiency, either stay close to “idle / no wake” speed or have fun and get up on plane. Plowing through the water wastes fuel and creates unnecessary wakes.
Proper engine maintenance also plays a significant role in fuel efficiency. So be sure that your engine’s recommended maintenance is always up-to-date.
Summary
Once you understand the fuel requirements, you’ll be better informed as a boat owner.
No matter the case, always ensure that you consistently follow the safety procedures when fueling. And whatever you do, don’t pump diesel into your gas boat!
Lastly, whether it’s gasoline or diesel, boat fuel tends to be pretty expensive. Therefore, you’ll need to find ways to save money. Reducing your boat storage costs is a great place to start (and something Neighbor.com can help with).
Neighbor is an innovative peer-to-peer storage marketplace offering convenient, nearby boat storage options. For more info, check out Neighbor’s boat storage near me.
