Boating and Fuel Economy – Part 1

Published On September 22, 2015 | By Mark Baese | Recreational Boating

If you’re buying a power boat thinking that it’s efficient means of travel, you really need to do more research. I’m pretty sure using gasoline to fuel your rocket powered rollerskate invention would be significantly more efficient.

That doesn’t mean it’s not important – it’s just that we need to have realistic expectations here.

In this first part, we’re going to explore exactly what fuel economy looks like in a boat: specifically my boat, and how bad it is. In part 2, we’ll look at the other options we’re looking into that will make this a little more manageable.

Before we start, I want to set a few ground rules. It’s really hard to measure boats in terms of Miles Per Gallon (MPG) like automobiles. The reason is that unlike the road, the water underneath you can be moving with you or against you due to tides, current, wind, etc. If it’s moving with you, you can get significantly better milage, and of course the inverse is also true.

IMG_2696

Let me give you an example:

My boat has a 125 gallon gasoline fuel tank (not diesel). I don’t know for sure – but based on tests of similar size boats using the same engine as me, I can expect to get about 1 mile per gallon (MPG) on average in completely slack water at about 1200 RPM in my 1995 Larson 280. It makes the math pretty easy – I can get about 125 miles on a tank of fuel before tide & currents are factored in. The faster I go, the less efficient I am.

If I burn one mile per gallon, that means I can travel one mile on one gallon. Now assume the water is moving in the same direction as us. At the end of one gallon, I’ve now actually travelled two miles, thus getting 2 MPG. Or, if the water was moving against us, it’s possible I’d only actually travelled 0.5 miles with that gallon. It’s impossible to accurately measure economy in real world conditions.

So how do you measure fuel economy in a boat? We use gallons per hour. It’s as simple as how many gallons are used per hour of the engine running at a certain RPM. This seems complicated, but it actually makes things a lot easier. Here’s why:

If  you know that at your current speed of 1200 RPM you’re burning 3 gallons an hour, and you’re currently travelling at 5 miles an hour, and you have 9 gallons of fuel on board – it’s easy to tell that you can make it 15 miles on your remaining fuel.

This can easily be calculated no matter what the water underneath you is doing, you just change your speed and leave the other variables the same. Your grade 8 self that thought you wouldn’t need math as an adult is throwing a fit right now.

That said, for the sake of this article, we’re going to assume water is as stationary as the road. No current, wind, tides, etc.

Like I said earlier, my boat gets about 1 mile to the gallon, or a range of about 125 miles on one tank. Terrible fuel economy.

Boat Range vs truck f150 tesla

Compare that to your standard 2WD Ford F150, which gets 25 MPG (highway driving), and the Ford seems insanely efficient. The Ford comes with a 23 gallon fuel tank, giving it a range of about 575 miles – significantly further than the boat.

A Tesla, where people often complain about range, can only go 265 miles on one charge. Nearly twice as far as my boat.

Where it really hurts, is the price of fuel. Marine fuel (91 octane) is costing me 1.79 a litre (6.77 CAD per gallon) at a marina pump for a total of $847 to fill up a tank. The Ford would cost me 0.99 cents a lire (3.74 CAD per gallon) right now at a standard gas pump for a total of $86 to fill up the tank.

So, the Ford can go 575 miles for about $86 dollars. We’ll use 575 miles as our baseline.

Using current electricity prices in British Columbia, a Tesla costs about 0.03 cents a mile – meaning it would cost about $17 to travel 575 miles.

For my boat to cover the same distance on the water, it would cost roughly $3896. That’s not a typo. Now you see why sailing is so popular.

Boat Fuel Economy vs truck f150 tesla

 

That’s just the cost for the fuel. Not to mention they need more frequent oil changes, along with all the other parts that need servicing.

There are many reasons why my boat gets such poor mileage. First, it’s a rather large boat at 29 feet using a single relatively old engine to drive a one prop.

No one gets into boating because it’s the most efficient method of travel though.

In Part 2 next week, we’ll talk about boats that get better fuel mileage. Sign up for our newsletter to get updates so you don’t miss that article, plus follow us on Facebook & Twitter.

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