Fuel economy might not have been a concern when you first bought your boat, but with gas prices on the rise the cost of fuel is top of mind for most boaters right now. We'll give you some tips on how to make your boat more fuel efficient so you'll feel less pain at the pump.
How to Cut Your Fuel Costs
1. Keep the Bottom Clean
A fouled bottom increases the drag on your boat meaning your engine has to work harder and burn more fuel in the process. Regularly applying bottom paint and Propspeed will both go a long way to keeping your hull and your running gear free of barnicles and other marine growth.
2. Tune Your Engine
Follow your engine manufacturer's service recommendations. Poorly running cooling or fuel systems will negatively impact fuel mileage and neglecting regular maintenance will also shorten the life of your engine. We carry outboard engine service kits for all major outboard manufacturers to make it easier to keep your engine running optimally.
3. Drive Smart
Handle throttles smoothly and only apply as much power as the situation requires. Get your boat onto plane efficiently rather than spending unnecessary time in the transition range, where fuel consumption can be relatively high. Once on plane, adjust throttle and trim to find an efficient cruising speed for your boat and conditions.
4. Don't Push Water
Proper trim is essential to good fuel economy. Running with the bow too low can cause the boat to plow through the water, increasing drag and fuel consumption. Excessive positive trim can cause porpoising and also reduce efficiency. If your boat doesn't trim properly, trim tabs can help you establish the proper running attitude. Outboard-powered boats may also benefit from hydrofoils, depending on the boat and application.Outboard powered boats can benefit from bolt-on hydrofoils.
5. Check Your Prop
Unless the blades are perfectly true, your boat propeller will fail to provide maximum thrust. Blades with nicks and dings create power-robbing turbulence and should be reconditioned.
Make a test run with your boat loaded the way you generally use it to be sure the fitted propeller allows your engine to reach the manufacturer's recommended wide-open-throttle (WOT) RPM range. Propeller pitch should be selected to keep the engine within that range; too much pitch can overload the engine and prevent it from reaching its recommended WOT RPM, while too little pitch can allow the engine to overspeed.
For more prop selection advice, check out our Selecting a Propeller West Advisor Article
6. Lighten the Boat
Fuel has weight too, but don't compromise your safety margin to reduce weight. Carry enough fuel for the planned trip while following the Rule of Thirds: one-third of the fuel to reach your destination, one-third to return and one-third in reserve.
7. Install a Fuel Flow Sensor
A fuel flow sensor can send real-time fuel-consumption data to a compatible NMEA 2000 multifunction display or instrument, allowing you to monitor fuel flow and fuel economy while adjusting throttle and trim.
A flow sensor also keeps up with total fuel consumed and it has the added value of providing early warning of developing engine and running gear problems or fouling.
8. Repower
A too-small engine works harder and can burn more fuel, meaning that in some cases, upgrading to a higher horsepower engine can actually be the more economical choice. 4-stroke outboards are generally more efficient than 2-stoke outboards as well so keep that in mind when it's time to upgrade.
Gallons per Hour versus Miles per Hour
It's no surprise to anyone that's ever swiped their card at the gas dock that boats burn a lot of fuel. While most anyone who drives a car is familiar with “miles per gallon” measure of fuel efficiency, for boats think “gallons per hour”.
A rough approximation of what this means for a gasoline outboard powered boat is to take the horsepower of the motor and divide it by 10. So for example, a 225 horsepower outboard running at full throttle will burn about 22.5 gallons per hour. That's a lot of fuel, but there are driving behaviors that can help bring that figure down.
Throttling back to 75 percent of full throttle can result in up to 50 percent less fuel burned. Throttling back even more will further reduce fuel consumption, but you can only throttle back so much before your time to destination is later than you need it to be. So the issue becomes, how much fuel are you willing to burn in order to arrive at your destination within the right time frame?
That is the proverbial “sweet spot” and will give you your ideal cruising speed and RPMs
How to Determine Your Boat’s Most Efficient Cruising Speed
To figure the optimum RPMs at which to run your engine that will get you to where you want to go at a cost and within a time frame you are willing to accept, create a four-column table like the one that appears below.
| RPM | MPH | GPH | MPG |
|---|---|---|---|
| 1000 | |||
| 1500 | |||
| 2000 | |||
| 2500 | |||
| 3000 | |||
| 3500 | |||
| 4000 | |||
| 4500 | |||
| 5000 | |||
| 5500 | |||
| 5700 |
Next, take your boat out and run it at each of the RPMs that appear in the left hand column. For more accurate results, make each test run in both directions and average the speeds. This helps minimize the effects of wind and current.
Then, using a GPS and your boat’s fuel flow gauge, fill in the MPH and the GPH for each of the RPM entries. After finishing your runs, you will need to do some, math. For each row in the table, divide MPH by GPH and note the answer under MPG.
Following is an example of the table filled in with values taken from a Yamaha Performance Bulletin for a single Yamaha F300XSB2 outboard motor mounted on a Pursuit DC 246 boat. To this table, we have added additional columns, shown in italics, assuming a fuel cost of $4.00 per gallon. The Cost/20 M Trip and Time to Arrive columns are based on a 20-mile trip.
| RPM | MPH | GPH | MPG | Fuel Cost/G | Cost/HR | Cost/20 M Trip | Time to Arrive |
|---|---|---|---|---|---|---|---|
| 1000 | 5.2 | 1.3 | 4.00 | $4.00 | $5.20 | $20.00 | 3.85 HR |
| 1500 | 7.1 | 2.1 | 3.38 | $4.00 | $8.40 | $23.67 | 2.82 HR |
| 2000 | 8.6 | 3.8 | 2.26 | $4.00 | $15.20 | $35.40 | 2.33 HR |
| 2500 | 9.3 | 5.5 | 1.69 | $4.00 | $22.00 | $47.31 | 2.15 HR |
| 3000 | 11.1 | 7.1 | 1.56 | $4.00 | $28.40 | $51.17 | 1.80 HR |
| 3500 | 15.4 | 9.4 | 1.64 | $4.00 | $37.60 | $48.83 | 1.30 HR |
| 4000 | 23.0 | 12.4 | 1.85 | $4.00 | $49.60 | $43.13 | 0.87 HR |
| 4500 | 33.6 | 15.7 | 2.14 | $4.00 | $62.80 | $37.38 | 0.60 HR |
| 5000 | 39.2 | 20.5 | 1.91 | $4.00 | $82.00 | $41.84 | 0.51 HR |
| 5500 | 43.8 | 26.5 | 1.65 | $4.00 | $106.00 | $48.54 | 0.46 HR |
| 5700 | 45.0 | 26.7 | 1.69 | $4.00 | $106.80 | $47.47 | 0.44 HR |
The table shows that, among the planing-speed entries, the best fuel economy is 2.14 MPG at 4,500 RPM, where the boat travels at 33.6 MPH and the engine consumes 15.7 GPH. At that speed, a 20-mile trip would require approximately $37.38 worth of fuel and take about 0.60 hour, or 36 minutes. The results you get will vary with your boat type, boat weight, propeller pitch, motor type and environmental factors such as wind speed, wind direction and wave action.
Fuel Flow Sensors
Garmin's GFS 10 Fuel Flow Sensor.
If constructing a table like the one above seems a bit tedious, there is another approach—one that will help you determine your fuel efficient “sweet spot” regardless of wave action or conditions. That approach is to install a fuel flow sensor.
When connected to a NMEA 2000 multifunction display or instrument, these sensors keep you abreast in real time of your fuel use in gallons per hour, how much fuel you have used and your remaining range based on current RPMs and how much fuel you have left. The dynamic nature of the algorithym enables you to accurately adjust throttles and trim for maximum economy even as wind and sea conditions change.
The Rule of Thirds
Fuel use in gallons per hour, miles per gallon, fuel remaining and range as seen on multifunction display.
Running out of fuel is a leading cause of boater distress. To avoid running out of fuel, when planning for a trip, always follow the Rule of Thirds. This rule dictates that you reserve one-third of your available fuel for arriving at your destination and one third of your fuel for the return trip. The remaining third should be held in reserve for unforeseen circumstances such as unexpected weather or towing another boat.
So for example, if you own the Pursuit DC 246 boat powered by the Yamaha outboard referenced above and plan on making a 20 mile trip while traveling at your “sweet spot” (33.6 MPH while turning 4500 RPM where you will burn 2.14 GPH), the minimum amount of fuel you will need to carry is 28.03 gallons. The easy way to calculate this is to triple the distance and divide that by 2.14. (3 x 20 = 60 miles/2.14=28.03 gallons)
Keep Your Engine Tuned Up
As mentioned above, keeping your engine tuned up and following a program of regular engine maintenance will help to contain your fuel costs. For do-it-yourselfers and professionals alike, West Marine offers a complete selection of outboard motor, inboard and inboard/outboard parts.
