The Burn Factor

Tips for keeping your vessel fuel-efficient

Front-view of the sport-fishing boat cruising across the water.
There are a number of ways to decrease your vessel’s fuel consumption, which will help the operation save money. Courtesy F&S Boatworks / Chris Rabil

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It’s no surprise to boaters that fuel costs are up. If you want to go fishing, take a family cruise, or even travel, there’s no way to avoid the pain at the pump. Seasonal long-distance runs along the Eastern Seaboard can also have you burning some unnecessary fuel. I am a big fan of chugging at 9 to 10 knots on long runs, which gets me optimal fuel burn when I compare the miles-traveled ratio. So, this leaves me wondering: How much fuel does a particular boat really burn?

If you’ve had your boat for some time, you’re likely pretty in tune with its idiosyncrasies, and you also probably have a good idea how much fuel you burn per hour both at different rpm and speeds. But factors such as how you use the throttle, whether your boat is overloaded, if it’s propped and trimmed ­properly, and the cleanliness of the bottom will all affect your fuel burn day to day.

Your engine’s electronic engine displays are designed to give you a wealth of information in real time, and there is plenty of accessible information that might help you on a number of fronts, with fuel-flow rate—or fuel burn in gallons per hour—as one of the most utilized. If your boat does not have a flow meter, I highly recommend that you install one if you want to enjoy optimal fuel savings. Using the tools you already have can easily help you figure out what your most economical cruising speed is, as well as what you’re burning at different rpm. Finding your boat’s best speed-to-­fuel-burn ratio will radically affect your wallet.

Trim It, Prop It

Trimming your boat to manage the ride in ­various sea conditions plays a major ­factor in fuel economy. Generally, there are two products we use to adjust trim. One is the tried-and-true trim tabs, and the other is interceptors. Regardless of which system you have, it’s important to always trim the boat properly so that it planes up with minimal hull-bottom surface area in the water. While this area will vary on sea condition and direction as it relates to your heading, if trimmed correctly, your boat will create less drag, which means better fuel economy. No matter the vessel, experimenting with trim will ­ultimately lead you to its most favorable ride.

Being correctly propped also plays a significant role in your boat’s fuel burn. At wide-open throttle, you should see a ­­100 ­percent load on the engine display, as well as the maximum manufacturer-stated rpm of your engine. If you’re unable to reach that stated rpm, or if you overrun it, then you are inaccurately propped in some way, which means you are not getting the most efficiency out of your vessel.

Whenever you haul out to repaint your bottom or do other annual maintenance, take the time to thoroughly inspect your props and send them out to be ­reconditioned if they show wear, dings, ­electrolysis or ­cavitation burns. I have found that ­running-gear ­coatings assist with fuel ­savings and efficiency as well by keeping marine growth at bay. While coating effectiveness is widely debatable, I have personally seen it make a difference in the past two high-performance sportboats that I have run.

Two sport-fishing boats docked at a personal boat dock.
No matter where you’re fishing, fuel prices are going up. Inspecting your boat’s bottom and ­running gear regularly is just one of the ways to mitigate some of those rising costs. Chris Rabil

Maintain It

Keeping your bottom and propellers slick, clean, and in good condition dramatically helps fuel economy. Boats that spend a lot of the time in the water, especially when they don’t move too often, are highly susceptible to marine growth. This growth increases drag and, in turn, decreases fuel economy, so it’s important to use the proper ablative bottom paint for your vessel.

Not all bottom paints are created equal, so do your homework. Multiple coats of built-up paint will also cause drag, so if your bottom has chips, or looks obviously rough, or if you find that the paint is no longer sticking, it might be time to soda-blast it off and start over. Ablative bottom paint can lose adhesion as multiple layers are applied over the years, so if you find that bottom ­cleanings are needed more frequently, it could mean the ablative properties are no longer as ­effective as they once were.

A maintained engine will always run more efficiently. Schedule your maintenance according to the manufacturer’s recommendations and service schedules in the owner’s manual. Basic maintenance, such as ­keeping your air and fuel filters clean, will greatly help with fuel efficiency, and because fuel quality can vary from location to location, it takes only one bad load of fuel to kill your filters. It’s easy enough to keep a sharp eye on the condition of your water separators and its elements. I check mine after every trip and change them every 80 to 100 hours, regardless of how they look. If they look dirty any time before that, I change them out right away. Fuel is one of the easiest things to maintain on a boat, and because most engine problems begin with fuel-related issues, it just makes sense to pay it some attention.

Lighten It

I am definitely guilty of carrying too much weight—equating to 1,000 pounds or more—on my boat. As a traveling operation, I need to carry a lot of tools and heavy spare parts so that if I’m ever in a jam, I will have everything I need to make a repair. However, when I’m at home, I usually do not remove all of this excess weight, which, admittedly, is a mistake: Added weight means more drag, which equates to more fuel burned.

Today’s boats have fuel and water tanks that are much larger than what is needed for a day trip, so by keeping these tanks just full enough—plus some “just in case”—can also help your fuel economy. Diesel fuel weighs approximately 7 pounds per gallon, gasoline weighs 6 pounds per gallon, and fresh water comes in at about 8.4 pounds per gallon. All of this liquid adds up quickly with large tanks. And while all of this weight makes sense for those fishing the Gulf of Mexico, or in the Northeast where runs offshore are 80-plus miles one way, it makes less sense for, say, a boat in the Florida Keys, where runs to the edge are only a few miles.

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I’m not saying in any way to leave the dock without more than enough fuel, water, tools, or necessary spare parts or safety gear, but I am saying that excess fuel you won’t burn, along with those unnecessary cases of drinks or spare parts that are strictly for at-the-dock repairs, don’t need to live on your vessel when you are fishing from your home base.

In all, keeping boat maintenance tight, learning how your boat runs best in certain sea conditions and at different speeds, and as lightening up on what you carry on board are some of the best ways to ensure that you make the most of your fuel economy. And we all could use a break in the cost-of-fuel department these days.

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