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outboard motor mpg

Old 07-11-2005, 07:39 AM
  #1  
Nontypical Buck
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Default outboard motor mpg

I was curious as to what kind of gas mileage everyone gets with their boats. I got an evinrude 115 rebuilt to a 140. This last weekend I ran out of gas. I had a full 18 gallon tank when I started and according to my GPS, I had run about 60 miles when I ran out. Fortunately, I was only a 1/4 mile from the boat ramp when it happened. That gave me an mpg of 3.33 miles per gallon. What does everyone else get for mileage. Also, does anyone have the new 4 stroke outboards and what kind of mileage do you get?
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Old 07-11-2005, 02:18 PM
  #2  
Nontypical Buck
 
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Default RE: outboard motor mpg

rocky,
When talking about boats,outboard or inboard engines you need to think of "Gallons per Hour" (GPH) - not - Miles per Gallon(MPG).

GPH is based on at least; speed,trim,load,prop,water,weather conditions(wave and wind action). Those 1st 4 are probably the most critical when talking GPH(assuming your engine is well tuned).
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Old 07-11-2005, 02:23 PM
  #3  
Nontypical Buck
 
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Default RE: outboard motor mpg

BTW - my son just bought a new 4 stroker Johnson last summer. Sweet little motor. Can hardly hear it run,almost smokeless,fuel economy is excellant. It however does not have the low end torgue of a 2 cycle.
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Old 07-11-2005, 09:03 PM
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Default RE: outboard motor mpg

GPH is more a term used to estimate WOT consumption and to get an idea of a motors true output (with carbed and EFI motors, they typically consume 10% of their rating at WOT in one hour, example a 200hp motor would use around 20gals at WOT for one hour).

As for mpg per motor, the largest variable is the type of boat it is used on. Obviously a 150 Mer EFI is gonna get better fuel mileage on a bassboat that it pushes too 60mph than it would on a 24' pontoon that barely goes 20mph. Greater distances covered with the same amount of output yields greater efficiency or fuel mileage. Thus the fact that hull design (which is a combination of both hydrodynamics and aerodynamics) has as much or more impact on fuel mileage than does the motor itself.

My personal boat is among the most efficient boats known. It is an Allison XB2003 ProSport that is 20' 03", the barehull weighs around 1k#s and the motor is a 225 ProMax SS (which is a EFI motor built by Mercs Hiperf division and actually dynoed 242 at the prop which means it made about 260-270 at the head). Most V-6 20'+ bassboats will get around 2-3mpg at 3/4 or better throttle. I average between 5.5-6.5mpg so call it 6. That is twice the fuel economy of most similar boats, here it's STRICTLY a matter or hull efficiency. (A couple years ago a major magazine tested a Allison SS2000 with a 115 Fict Evinrude and got a maximum mpg rating of 12, and the boat would run over 80 on the top end. Basically unheard of in anyother types of boats!) Another benefit to hull efficiency is greater speed with less horsepower. My boat will run over 90mph. Most hulls that same size with the same motor will be doing good to run 75mph. That extra speed yields increased fuel effeciency.

The new DFI motors like Mercs OptiMax, Yammies HPDI and Bombs Fict are quite fuel stingier than their carbed and EFI counterparts. Getting 1 or 2 more mpg doesn't sound like much. BUT when you realize you can be talking about a 2mpg boat now getting 2.5-3.5mpg you are seeing differences of 25-75% better fuel economy. For the more performance oriented boater they hold more promise than the current technology of 4stroke outboards.

As for the 4strokes, they have some advantages like quieter, smoother and typically better fuel economy at low speeds. The dis-advantages are their extra weight (which creates more drag and decreases efficiency, example: 225 Optimax is 520#s, 225 Verado 630#s) they typically have no better and maybe even worse fuel economy at 3/4 or more throttle compared to similar output 2strokes. Another overlooked thing about the 4strokes right now, you can run a 2 stroke until it blows and rebuild most of them for a couple thousand at most. No one really knows what it would cost to rebuild the 4strokes, but most estimates put it at basically scrapping the engine and starting anew.

3.3mpg with a 115 is in the moderate/high range for fuel consumption for motors that size.
RA
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Old 07-12-2005, 06:39 AM
  #5  
Nontypical Buck
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Default RE: outboard motor mpg

Hey Red, what color is that allison?I appreciate all the info from both of you. My boat and motor are both 1984 models. The motor was rebuilt two years ago to a 140, that's what I was told anyway. The hull of the boat leaves a lot to be desired. I've got to run trim tabs to keep it from porpoising and I know that's killing my performance. I only got $1800 in the boat, motor and trailer and it's got all the electronic gear. I use to bass fish all the time, all over the south, but I developed some back problems and I sold my boat and quit. Last year my wife and I were fishing below pickwick dam, from the bank, and she caught a 5-1/2 pound smallie and she was hooked on fishing. I bought this old used boat to see if I really wanted to get back into fishing and to see how far she wanted to take it. So far we've had a great time and I imagine next spring, I'll be upgrading that old boat. Anyway, thanks for all that knowledge you'll have shared.
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Old 07-13-2005, 11:17 AM
  #6  
Nontypical Buck
 
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Default RE: outboard motor mpg

My brother in law has a 34' Sea Ray with Twin 454's.

It burns nearly 25 gallons per hour. At marina gas prices ($2.90) that's nearly $75 for each hour of use. He has it on Lake Erie. A trip to the islands runs him a couple hundred bucks in gas. Throw in a $50 docking fee and you have a small fortune in a trip.

OUCH!
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