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How Not To Run Out Of Fuel

Running out of fuel on the water isn't just embarrassing; it can also be dangerous to unexpectedly lose power. Here are five pointers that will help you avoid this common problem.

TowBoatUS delivering fuel

Last year, TowBoatUS responded to more than 4,600 cases of fuel-related breakdowns. Get into the habit of refilling your fuel tank after every outing, and you'll be less likely to run out. (Photo: Jason Arnold)

Running out of fuel is the fourth most common reason people call TowBoatUS for assistance. It's also one of the most embarrassing situations that can arise, because any competent captain can avoid inadvertently emptying the fuel tank with a little bit of foresight and care. You say you'd like to ensure that you never run out of fuel again? There are no guarantees in life, but these five simple pointers will go a long way toward helping you keep that gauge off "E."

1. Never trust the fuel gauge on a boat.

What we just said about keeping your fuel gauge off "E"? Well, fuggedaboutit. Whether your gauge shows a tank filled to the brim or nothing beyond fumes, you need to keep track of how much fuel is in your boat by other means. There are several reasons for this: In some boats, oddly shaped fuel tanks built to fit into the V-shape of the hull may show half a tank when, in reality, you've already burned through three-quarters of your supply. In some other boats, reading the gauge while the boat's at rest can give you a very different result than reading it while the boat's on plane. And in all boats, when you're out on the water, all the sloshing that takes place can give you erratic or inaccurate readings. Not only are fuel gauges on boats notoriously inaccurate, on new boats they may or may not have been properly calibrated at the factory. The bottom line? Keep track of how much fuel is in your tanks with the methods outlined below and/or a logbook, but never trust those gauges to be telling it like it is.

2. Live by the adage "one-third out, one-third back, one-third in reserve".

Keeping track of just how much fuel you've burned so far is much easier with newer boats than with older ones because most built these days display digital fuel-flow data at the helm. Keep track of consumption and consider a full third of your fuel capacity in reserve, and the chances of ever running out go way down. Is this somewhat excessively cautious? Absolutely. Many experienced mariners consider a 10% fuel reserve sufficient. And most of the time they're right. But planning on a full third of reserve is about as safe as it gets. And taking it down to 10% can result in extra "sloshing" in the tank which is likely to stir up debris or sludge.

3. Fill your tank up after each and every trip, whether you need to or not.

Do so, and you'll always leave your slip knowing you have plenty of fuel aboard as well as knowing the amount of fuel, assuming you know your tank's capacity. Plus, there's an added bonus to topping off each and every time: Keeping that tank full will help reduce condensation buildup in your tanks, which can become problematic if you regularly leave the boat sitting with lots of extra space in the tank for days or weeks at a time.

4. Know your boat's fuel burn.

Pop quiz: How many miles per gallon does your boat get on average at your regular cruising speed? If you don't know the answer off the top of your head, how will you ever be able to keep track of how much range you have at any given time? Serious mariners will want to know not only the average burn, but what the burn rate is at different cruising speeds. Consider a 28-foot bowrider with twin 200-hp outboards, for example. At a 3,500 rpm cruise in the upper 20-mph range, it might get around 2.5 miles to the gallon. But when cruising in the upper 30-mph range at 4,500 rpm, efficiency may well drop to about 2 mpg. That's a substantial difference, one that could mean reaching the next fuel dock with no problem, versus calling TowBoatUS for assistance.

Fuel flow

Most modern boats are equipped to display fuel burn, miles per gallon, and additional data at the helm. (Photo: Lenny Rudow)

5. Be aware of changes in conditions that can affect fuel burn.

Several environmental factors can have a huge bearing on that mile-per-gallon efficiency data you just calculated for your boat. Sea state can be an important one because a boat running on flat water will enjoy far better efficiency than one pounding against waves all day. Just how much of a difference it makes will vary from boat to boat and the specific conditions, so we can't give you any solid figures in this regard. What we can say is that it's more important than ever to keep careful tabs on your supply when it's rough. Fighting a current versus boating with a tailwind makes a difference, too. And another contributing factor is how clean your boat's bottom is, or not. If you're dragging a bunch of barnacles around with you everywhere you go, fuel efficiency can suffer dramatically.

Always remember that there are countless factors coming into play when considering fuel burn. How heavy the load is and weight distribution in the boat, how the trim tabs are used, how the drive(s) are trimmed, the condition of your propellers, and many other variables can all have an effect. But if you keep these five tips in mind and use a healthy dose of common sense as you go boating, your chances of running out of fuel will plummet. Still, of course, there's always some possibility that due to a mistake or a mechanical malfunction, one day your tank will run dry shy of the dock. And if that ever does happen, hopefully you have a BoatUS towing membership

Bonus Tip

Portable fuel tank

If you have a small boat with a standard portable tank and your engine sputters to a stop, remember that most portable gas tanks have a ridge molded into the bottom that separates one side from the other. By tilting the can toward the side with the pickup, fuel will flow over that ridge, and you can often get moving again.


Lenny Rudow

New Boats, Fishing & Electronics Editor, BoatUS Magazine

Top tech writer and accomplished sports fisherman, BoatUS Magazine Contributing Editor Lenny Rudow has written seven practical boating books, won 30 awards from Boating Writers International — many for his marine electronics articles – and two for excellence from the Outdoor Writers Association of America. He judges the NMMA Innovation Awards, and is Angler in Chief at FishTalk, his own Chesapeake-based publication. A great teacher and inspirational writer, Lenny hosts many of BoatUS Magazine’s very-popular how-to videos, which can be found on the BoatUS YouTube channel, or at