power and fuel mileage. need opinions.

i was reading an article in my news feeds yesterday that said that a boat with a higher power engine will burn less fuel than the same boat with a smaller engine. say at a 30mph cruise. http://www.boatbanter.net/engines/how-much-power-need/ it made sense and i found an article on boating mag i think that gave some data based on 5000 miles of cruising. should have bookmarked it cause i can't find it now. does anybody have any experience with this? is the fuel savings worth the extra cost of the engine?

Re: power and fuel mileage. need opinions.

every boat is different, and that might be true for one boat, but completely false for another. There are a HUGE number of variables that you can play with to make either engine come out on top.

The biggest thing is how you drive though. If you have a bigger engine, you will tend to cruise at a faster speed, and there goes your MPG's anyway.

Re: power and fuel mileage. need opinions.

Fisher3491 said:

i was reading an article in my news feeds yesterday that said that a boat with a higher power engine will burn less fuel than the same boat with a smaller engine. say at a 30mph cruise. http://www.boatbanter.net/engines/how-much-power-need/ it made sense and i found an article on boating mag i think that gave some data based on 5000 miles of cruising. should have bookmarked it cause i can't find it now. does anybody have any experience with this? is the fuel savings worth the extra cost of the engine?

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Depends on how long you will keep the boat. More importantly is that when you get a slightly bigger motor than you might want you are less into the throttle that makes for less wear and tear on the engine.

Re: power and fuel mileage. need opinions.

Power and fuel economy go hand in hand. The more power, the better the economy. Right?

Re: power and fuel mileage. need opinions.

I believe as a general rule, The bigger motors do get better economy than a smaller one on the same boat. Right up to the point where your, really getting with it. Then you can go faster or have a larger load, and the mileage will drop a bit.

Re: power and fuel mileage. need opinions.

I bet there is a point where that benefit tapers off. Sure, a smaller engine being worked to death will likely use more fuel than a larger engine that's just essentially loafing along. But taking an engine that has no problems powering the boat, and putting in an even larger engine, I bet at some point the curve would reverse itself.

Re: power and fuel mileage. need opinions.

I am not sure if I am buying that story.... I've heard that in the auto forums as well. Too many other variables, speed, hull design, weight, etc... I will agree to buy the larger engine for the hp hull rating, but only due to performance advantages. Obvioulsy if you go way out side the size recommendation, perhaps smaller is worse. You put a 3.0L in a 19ft and a 5.0 in a 19ft, give me a gallon of gas and bet I'll go further on the 3.0L.

Re: power and fuel mileage. need opinions.

It would be almost impossible for the average boater to recover the costs of changing over an outboard based just on fuel savings. This is especially true with such small outboars.

Fisher, on average, do you burn more than 100 gallons of fuel per year in your boat? More than 500? To justify the expense just based on fuel savings, you have to keep in mind that your increase in efficiency is going to amount to a small percentage in terms of gallons saved per year.

So for example, if you improve by a whopping 10% and you burn 250 gallons per year on average, you'll have saved 25 gallons. Which at today's prices is roughly $100.

Of course, I stronly suspect that the average boater doesn't burn anywhere near that quantitiy of fuel, especially in a 30 HP, so you can see that it would take forever to pay for an engine swap just based on fuel.

It just doesn't make sense for small outboards. Yes, for the guy running a walkaround with twin 150s and burning 1500 gallons a year, even a 10% improvement could make it worthwhile. But then if you're going to go through the whole repower hassle, why not go to a ETEC or 4 stroke and get a 25-50% improvement?

Grouse

Re: power and fuel mileage. need opinions.

This magazine article in the June 2010 Boating magazine compared a 23' Stingray I/O with a 4.3L (3.92 MPG), a 5.0L (4.42 MPG), and a 5.7L (4.84 MPG). They also compared a 23' Grady White OB with a Yamaha 250 (2.78 MPG) and a Yamaha 300 (3.16 MPG). Biggest engine had best economy in both cases.

Re: power and fuel mileage. need opinions.

Fisher3491 said:

i was reading an article in my news feeds yesterday that said that a boat with a higher power engine will burn less fuel than the same boat with a smaller engine. say at a 30mph cruise.

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So in theory, if you had a high enough powered engine, it would burn no fuel at all, right?

I'm not sure I'm buying that theory.

Re: power and fuel mileage. need opinions.

I was just thinking about this topic yesterday as I was cruising down the river...

I had a 4.3L powered Baja Islander 18 footer. I recently bought a 454 powered Baja Hammer (almost 22 foot). I haven't put a pen and paper to it yet, but the Hammer seems to burn twice as much gas at 30-35 mph as the Islander did. Of course its a bigger boat, but its not that much bigger.

Now the good part, the Hammer is running 2800 rpms at 30 mph... I can accelerate to 40 mph and I'm only turning 3150 rpm's. At 40 mph, I can run for a long time and the gas gauge won't drop, but if I slow down... its sucking the $100's right out of my wallet.

I guess lots of factors weigh in, but I'm glad I have a big block!!

Re: power and fuel mileage. need opinions.

So in theory, if you had a high enough powered engine, it would burn no fuel at all, right?

I'm not sure I'm buying that theory.

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What's wrong with that theory? Drop a breeder reactor in your boat, and you'll actually be MAKING fuel!