Fuel Saving Tips When Using Your Boat

No one wants a trip out on the water to be something that results in a significant dent in your wallet.  Although some electric battery powered outboard options exist, they’re far from popular.  Nearly everyone’s outboard engine runs on gasoline with some boaters using diesel engines.  Unless your engine is one of the very few that runs on a battery, using your boat inevitably involves purchasing fuel.  “How much fuel will it burn?” is one of the most frequently asked questions by boaters looking to purchase a new outboard, or a new boat and outboard engine combination together.  The answer to that question is not as simple as providing an answer for fuel consumption in a car.  You may not realize that the amount of fuel your boat consumes is largely determined by factors you have control over.  The manner in which you run your boat; either all out, wide open throttle (WOT), or at a lesser speed, allowing for a more efficient correlation between RPMs and fuel consumption, will make a difference.  The way you load your boat and how much weight you add to your boat are additional major factors.  More than a half-dozen user controlled contributing factors need to be considered when calculating your boat’s fuel consumption.  Most people can easily figure out their car’s fuel consumption by dividing the distance traveled by the number of gallons used.  Calculating the fuel efficient of your boat involves different factors and a different formula.  Ultimately, fuel economy is improved by a combination of tactics that incrementally result in your boat using less fuel.  Below, we’ve listed a few tips to help you save fuel when out on the water.

Heading offshore 1

Choose the Right Prop

Selecting the right boat propeller is an important factor in maximizing your boat’s performance. Determining the correct size and style of boat prop will keep the engine operating within its recommended rpm range and allow it to apply its maximum horsepower to the water.  You need to be sure you’re selecting the right size propeller.  The size of a boat propeller is determined by referring to both diameter and pitch.  Diameter is twice the distance from the center hub of the propeller to the tip of any blade.  Generally smaller diameter props correspond with smaller, lower horse power engines.  Correspondingly, larger diameter props correspond with larger boats. Pitch is the forward movement of a boat propeller through one complete revolution measured in inches. Lowering prop pitch will increase acceleration and pulling power. A higher pitch prop will make a boat go faster; provided the outboard engine has enough power to keep the rpms in the optimum range. If your boat’s outboard engine doesn’t produce enough power to run a higher pitch prop, your overall performance will suffer.  Moreover, you can cause expensive and sometimes irrevocable engine damage.  Many factors come into play when selecting a propeller.  So numerous are the factors that propeller selection alone is the proper subject of an entirely different article.  There are differences in propellers such a rake, skew, and cup.  Ultimately, the message we here at Live to Fish want to convey is that there is a significant degree of importance associated with choosing the right propeller.  The correct propeller helps ensure maximum engine life and minimize wasted fuel consumption.

Optimum Trim

Utilizing trim tabs and properly using the tilt and trim on your outboard engine, will allow you to reduce the drag created by your boat’s hull as it moves through the water.  Reducing drag allows you to save fuel.  You will never be able to optimize your boat’s fuel efficiency if you don’t optimize your boat’s trim.  A properly trimmed boat has only the minimal amount of hull running through the water.  How do you know if you’ve got the minimum amount of your hull in the water?  Keep trimming out until your propeller begins to cavitate.  Cavitation occurs when the formation of air vapor is drawn into the water your boat is running through by the propeller.  You’ll know it’s occurring when the sound of your engine running changes dramatically.

Hard tops, T-Tops, and Towers

Opening or closing windshields, and raising or lowering canvas enclosures can help improve fuel efficiency.  Canvas enclosed T-tops, hardtops, towers and Bimini tops all create aerodynamic drag, causing the engine to work harder to make the boat go at any given speed.  On certain boats,  having canvas enclosures up can lower a boat’s top end speed by as much as 3 to 5 mph.  It’s important to note that not all T-Tops are the same.  There are some T-Tops that actually increase fuel efficiency by acting as a wing and creating lift.  A t-top’s ability to create lift is highly debated.  Boat manufacturers and t-top manufacturers will swear that their design creates lift and reduces drag.  Lift is produced when the air traveling over the top of a surface produces less pressure than the air traveling beneath the surface.  The problem with claims concerning a t-top’s ability to create lift is that water is close to 1,000 times more dense than air.  Because water is involved in determining lift given the substance your boat’s hull is running in, actual lift would normally not be something your boat would be capable of experiencing; regardless of the design of your t-top.  Another problem with these claims is the speed that air planes travel at versus the speeds most boaters travel at.  Lift could be a factor when the boat is traveling at 70 to 80 mph.  How often you travel at such speeds would be specific to you and your boat design.  The best course of action is to use your boat with any enclosures open to allow for the passage of air.  You can experiment by next closing certain enclosures and determining how much an impact on your fuel efficiency closing that enclosure has.

Back Off, Burn Less

Unless you’re competing in a fishing tournament, trying to make it over an area known to be shallow before the tide drops too much, or simply pushing the throttle to it’s limits in an effort to satisfy that need for speed that lives in most of us, slow down.  You’ll experience significant fuel savings without costing you any real time.

Put Your Boat on a Strict Diet

One of the quickest ways to get more miles per gallon is to reduce the weight you’re carrying.  What’s true for your car is true for your boat.  Most boaters are guilty of carrying too much gear.  A majority of the accumulation of the extra gear occurs slowly throughout the time you own your boat.  One tackle box, one water ski, and perhaps one additional gadget at a time. One of the quickest ways to get more miles per gallon is to remove items you don’t need.  We’re not suggesting that you remove tools, spare parts, or other safety items.  However, you don’t need all the fishing gear if you’re not going to be fishing.  You don’t need water skis or a wake board stowed below if you’re not going to be doing any of either.  If you store twelve packs or more of other types of drinks, just in case, removing those cases before you leave the dock will result in you saving more fuel.

Clean, Smooth, Hull


Karl Sandstrom, a 21-year veteran with Evinrude, explained, “a clean, smooth bottom is a real efficiency enhancer.” If you keep your boat at a slip or mooring, use a quality bottom paint.  Traditional hard bottom paints are effective at reducing fouling on your hull, but hard bottom paints create a cratered surface after a few years of built-up coats. If you notice such craters on the bottom of your boat, use a scraper, hire a diver to clean the bottom, or have your bottom cleaned with a bead blaster to remove old cratered paint.  Joel Macri, captain of the Pershing Motor Yacht Milagros explained, “we have our bottom cleaned once every month with a diver.”  Once a month may sound extreme, but so is the vessel Captain Macri is piloting.   The Milagros boats twin MTU diesel’s turning out 2,638 HP each, for a total of 5,275 HP, turning twin propellers that are 4.5″ feet each in diameter.Photo of the Pershing Propellers

Maximizing efficiency as to your boat’s hull can be achieved through selecting what are called ablative paints.  Ablative paints are also known as self – polishing bottom paints.  It is a softer paint and allows the coating to wear off at a controlled rate.  A good comparison would be to imagine a bar of soap.  The wearing away of the self-polishing bottom paint allows for new, un-oxidized paint to be exposed. If you normally keep your boat on a trailer, or it comes in and out of the water for any reason, the paint will oxidize within 72 hours. Once placed back in service, the oxidized ablative paint wears away and exposes a new fresh outer coating with active protection. Ablative bottom paint is engineered with more recent and advanced technology than the traditional hard bottom, bottom paints.  It is the preferred bottom paint of most users since it typically lasts longer and continuously exposes a new active outer coating that protects against marine growth.

Calculate Your Boat’s Fuel Consumption:

A formula you’re probably familiar with for calculating how much gas your car uses is one in which you divide the total miles traveled by the total gallons of fuel used.  Once you have the total number of miles, you divide that by gallons to get what is called your average fuel consumption.  For boating, there is a different formula for calculating how much fuel you’re burning.  A different formula is necessary because the conditions a boat must encounter and travel over are different than what a car’s engine has to deal with.  Sea conditions vary more widely than road conditions.  The time it takes to cover a distance with a boat as opposed to car varies more often due to the significance of other factors not found on the road.  As a result, your boat’s fuel consumption is measured in gallons per hour (GPH). You measure fuel efficiency in pounds of fuel used per horsepower developed per hour. Boating lingo associated with fuel consumption will sometimes refer to the fuel consumption calculation as the, “brake – specific fuel consumption.”  In calculating fuel consumption for your boat, it’s important to know that gasoline weighs about 6.1 pounds per gallon and diesel fuel weighs about 7.2 pounds per gallon.  Generally, gasoline engines burn about 0.5 pounds of fuel per hour per horsepower unit.  On average, an in-tune four-stroke gasoline engine will burn about 0.50 pounds of fuel per hour for each unit of horsepower.  A well-maintained diesel engine burns about 0.40 pounds of diesel fuel per hour for each unit of horsepower it produces. These figures don’t take drag of the boat, sea conditions, or efficiency losses through transmissions and bearings into account. However, these figures do provide an excellent relative difference between engines.

Formula To Estimate Maximum Engine Fuel Consumption

GPH = (specific fuel consumption x HP) divided by Fuel Specific Weight

Constants in the formula are the Weight of a Gallon of Gas vs. a Gallon of Diesel

Specific Fuel Consumption:

Gasoline Engine: .50 lb. per HP.

Diesel Engine .40 lb. per HP

Fuel Specific Weight:  Gasoline: 6.1 lb. per gal. Diesel: 7.2 lb per gal.

300-hp Diesel Engine Example:  GPH = (0.4 x 300)/ 7.2 = 120/7.2 = 16.6 GPH

300-hp Gasoline Engine Example: GPH = (0.50 x 300)/ 6.1 = 150/6.1 = 24.5 GPH

Keep in mind that these formulas apply when the engine is making peak horsepower, which usually is near wide-open throttle. Fuel consumption will be decreased at cruising speeds.

Another way is to take the total engine horsepower and divide it by 10 for gas engines or .06 for diesel engines. That formula is simpler to calculate and easier to remember. You don’t even need a pencil and paper. However, it’s not going to be as accurate as the formulas above. The result represents the approximate gallons per hour the engine will burn at wide-open throttle. For example, a 150-horse engine will use about 15 gallons per hour. However, that figure is an average.  It can vary by as much as 10 to 20 percent.

There are marine electronics that can help in determining your boat’s fuel efficiency available from our website, www.livetofish.com One that is used for measuring your boat’s fuel efficiency is the Lowrance Fuel Flow sensor.  If you don’t see something you’d like or need on our website, feel free to contact us at 1-844-934-7446, email at: contactus@livetofish.com or visit our showroom: Live to Fish, 9942 State Road 52, Hudson, FL 34669Building Front

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