How Fuel Efficient Are Outboard Motors?

Outboard motors are the most common marine propulsion type for small watercraft because of their compact design. Generally, fuel efficiency can be summarized by taking the horsepower rating and dividing it by 10 and you get the gallons per hour number, but this article goes a little more in-depth.

To find much of the data on specific motors, I used

How fuel efficient are outboard motors on average?

By using the most popular outboard brands, I found the average of their fuel efficiency based on how much horsepower they had. Here are the results:

Motor HorsepowerAverage Fuel Efficiency
10 hp1 GPH
25 hp2.5 GPH
40 hp3.9 GPH
50 hp4.7 GPH
60 hp5.5 GPH
70 hp7.3 GPH
90 hp9 GPH
115 hp10.8 GPH
135 hp13 GPH
150 hp15 GPH
175 hp16.5 GPH
200 hp19.5 GPH
225 hp21 GPH
250 hp24.5 GPH
300 hp26.2 GPH
350 hp33.5 GPH
400 hp38 GPH
600 hp51 GPH
GPH = gallons per hour

The general rule of thumb is to take how much horsepower your motor has and divide it by 10. This will give you a good estimate on how many GPH you would be using.

Note- This is assuming you are driving near full speed the whole time, true numbers will vastly vary. The slower you go the less GPH it will be, but you will obviously not go as far in that hour.

What outboard brands are the most fuel efficient?

  1. Suzuki
  2. Yamaha
  3. Tohatsu
  4. Honda
  5. Mercury
  6. Evenrude

When it comes to fuel efficiency, all of these are very similar, but Japanise made outboards tend to be slightly more fuel-efficient.

How can you make your boat more fuel efficient?

The lower your boat wieghs, the more fuel efficient it will be. So getting a good bulg pump to get rid of water in the hull will help eliminate some weight.

Also, making sure your engines are running well and you are only using 91 rated fuel or no ethanol fuel will help keep your motors as efficient as possible.

Many people tend to idle a lot. Simply turning your engines off when you don’t need them will help use less fuel.

Lastly, just toning the throttle down slightly to 75% when traveling could save you loads of fuel.

How much do you spend each year on fuel for outboard motors?

Obviously, this number depends on how large your motor is, but we can do some calculations based on fuel efficiency. If you assume that you use your boat for 50 hours per year, here is how much gas you would use and how much it would cost:

HorsepowerGas Usage Per YearGas Cost Per Year
10 hp50 gal$125-$200
25 hp125 gal$313-$500
40 hp195 gal$488-$780
50 hp235 gal$588-$940
60 hp275 gal$688-$1,100
70 hp365 gal$913-$1,460
90 hp450 gal$1,125-$1,800
115 hp540 gal$1,350-$2,160
135 hp650 gal$1,625-$2,600
150 hp750 gal$1,875-$3,000
175 hp825 gal$2,062-$3,300
200 hp975 gal$2,438-$3,900
225 hp1,050 gal$2,625-$4,200
250 hp1,225 gal$3,063-$4,900
300 hp1,310 gal$3,275-$5,240
350 hp1,675 gal$4,188-$6,700
400 hp1,900 gal$4,750-$7600
600 hp2,550 gal$6,375-$10,200
assuming $2.5-$4 per gal

Are inboard motors more fuel efficient than outboard motors?

After comparing the two, inboard motors tend to be slightly more fuel-efficient than outboard motors. It is not by much though, it’s only about 0.5 to 2 GPH difference at most, so practically the same.

The data was collected comparing the Volvo Penta and Mercruiser with all of the outboard brands. An example of this difference is the Mercruiser 4.5 MP1 250 hp gets 19.7 GPH, while the Yamaha 250 hp motor gets 23.8 GPH. Both engines are V6.