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Author Topic:   1998 OUTRAGE 20 Fuel Economy

Smithsm posted 05-23-2009 07:56 PM ET (US)
For all you experienced performance guys: Consider a 1998 Outrage 20 (2,200-lbs hull), with 2000 FICHT RAM 225 (506-lbs) and 15-1/4" x 19" MIRAGEplus propeller; 30- gallons of fuel, three people, no big coolers of ice, no T-Top, and a bimini
Will this boat exceed 3-MPG at 25- to 30-MPH cruise?
an86carrera posted 05-24-2009 07:39 AM ET (US)
I have a 200 ficht on a 22' with a T-top and get 3mpg.
So you might.
Len
Peter posted 05-24-2009 08:48 AM ET (US)
Should be acheivable. With a 19 inch pitch propeller, you should be able to see 30 MPH at about 3500 RPM. At 3500 RPM, your Ficht should be burning approximately 8 GPH.
jimh posted 05-24-2009 09:55 AM ET (US)
To get 3-MPG at 25-MPH the fuel burn rate has to be
1-gallon/3-miles X 25-miles/1-hour = 8.33-GPH
We now consider how much horsepower the FICHT motor can produce with 8.33-GPH fuel burn. For this we need to know the brake specific fuel consumption of the motor. We estimate this to be about 0.5-lbs/HP-Hour
8.33-Gallons/1-hour x 6.25-lbs/1-gallon = 52-lbs/Hour
52-lbs/1-hour x 1-HP-Hour/0.5-lbs = 104-HP
Can 104-HP move the boat at 25-MPH? Now we turn to Crouch's Calculator. According to Crouch, if we figure the HULL FACTOR =180, with 104-HP we can go 25-MPH with a total weight of as much as 5,391-lbs.
The estimated weight of the OUTRAGE 20 can be calculated as follows:
HULL = 2,200
MOTOR = 510
PROPELLER =15
FUEL = 200
CREW = 700
MISC = 700
TOTAL = 4,325
Since the total weight of 4,325-lbs is less than Crouch's calculated weight, we should be able to reach 25-MPH with less than 104-HP. If our estimate of the brake specific fuel consumption was accurate, then we will hit our fuel economy target of 3-MPG.
jimh posted 05-24-2009 09:59 AM ET (US)
By the way, my analysis is not based on experience. It is based on an understanding of the principles of naval architecture and conversion of fuel to power.
jimh posted 05-24-2009 10:27 AM ET (US)
In a prior discussion
http://continuouswave.com/ubb/Forum4/HTML/004149.html
some observed data about the BSFC of a FICHT engine was given. The BSFC was estimated at about 0.57-lbs/HP-Hour. Let's revisit the problem with that number:
Target fuel burn rate is 8.33-GPH
BSFC is 0.57-lbs/HP-Hour
Horsepower is then
8.33-Gallons/1-hour x 6.25-lbs/1-gallon x 1-HP-Hour/0.57-lbs = 91-HP
Maximum weight for
HULL FACTOR = 180
HP = 91
MPH =25
calculates to 4,717-lbs. This is still greater than our estimated total weight for the boat, so we should still be able to reach the target fuel economy.
jimh posted 05-24-2009 10:36 AM ET (US)
Let's try this again at the upper speed range of 30-MPH. Our fuel burn rate will be 10-GPH. This allows the horsepower to be 110-HP. Crouch says maximum weight has decreased to only 3,960-lbs. This means our OUTRAGE 20 total weight probably will exceed this figure. Thus the fuel economy at 30-MPH will likely not reach 3-MPG.
The outcome in the real world will depend on the nature of the hull and where it really likes to run for optimum efficiency. It has been my observation--now I am using my experience--that for Boston Whaler boats in the 20-foot to 22-foot range there will generally be a speed in the range of 24-MPH to 28-MPH where the boat will produce the best fuel economy. The outcome depends a great deal on how the boat is set up, and particularly the propeller being used. I suspect that with a 1998 OUTRAGE 20 there will very likely be a particular speed where you can hit a fuel economy of 3-MPG in the 25- to 30-MPH range.
acseatsri posted 05-24-2009 12:11 PM ET (US)
My Outrage 22 with E-TEC 225, T-top, full fuel, and 3 people aboard gets over 3-MPG anywhere from 18 to 35-MPH, with best economy (3.3-MPG) between 24 to 28-MPH. Jim's numbers are spot on.
Smithsm posted 05-24-2009 04:13 PM ET (US)
If I understand this correctly - my take on the calculation USING MY WEIGHT ASSUMPTIONS, I will be able to get 3 mpg at 30 mph because I see the total weight as less.
here is my weight estimate:
HULL = 2,200
MOTOR = 510
PROPELLER =15
FUEL = 200
Batteries - 110
CREW = 545 (230, 115, 200)
Tackle Box = 20
MISC = 200
TOTAL = 3,800
while crouch says we could do 3960 pounds at 10 gph at 30 mph
this all means I am optmimistic that I will get the results mentioned by acseatsri....
acseatsri posted 05-24-2009 12:11 PM ET (US)
--------------------------------------------------------------------------------
My Outrage 22 with E-TEC 225, T-top, full fuel, and 3 people aboard gets over 3-MPG anywhere from 18 to 35-MPH, with best economy (3.3-MPG) between 24 to 28-MPH. Jim's numbers are spot on.
acseatsri posted 05-24-2009 06:56 PM ET (US)
If you are using 3 MPG as a figure to determine offshore range, I would use 2 MPG as the divisor. If plowing thru heavy seas, I often have to pull it back to 12 MPH with the tabs fully extended, which gets me 6 GPH for a net of 2 MPG, worst case scenario.
phatwhaler posted 05-24-2009 07:01 PM ET (US)
You ought to be able to exceed 3mpg easily with a Ficht.
My 200 Merc with carbs will give me a hair over 3mpg at cruise. I have a T-top also.
Smithsm posted 05-24-2009 07:11 PM ET (US)
[Could we start using that SHIFT KEY to capitalize the intial letter of the initial word of each sentence, please?--jimh]
[A]n interesting theoretical question (at least for me) is how the [fuel economy] might be expected to change were the boat powered by a lighter 175- or 150-HP engine. [T]he engine would no doubt spin a less agressive prop fast to get to the 24-28 mph hull sweet spot
but
would there really be any fuel savings by using the lower displacement engine?
[I]f I understand JimH's models, I don't see exactly what variable, other than lower engine weight of 80 pounds would change; therefore the [fuel economy] may not be improved via a smaller engine on the 20-foot boat. [A]m I missing something or is MPG relatively independent of the horsepower on the outboard so long as the combustion efficiency is similar?
jimh posted 05-24-2009 07:24 PM ET (US)
You're into a whole new arena of speculation when you want to discuss engine efficiency as a function of engine displacement. If you really want to go there, start a new thread.
As for the extra 700-lbs I assigned to your weight estimate, that is based on my experience. Boats always weigh more than you think. For example, you did not allow for the batteries, the anchor, the oil tanks, the usual gear you'll have on board, and other "stuff." It all adds up. The only way to really know how much the boat weighs is to take it to a scale.

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Author	Topic: 1998 OUTRAGE 20 Fuel Economy
Smithsm	posted 05-23-2009 07:56 PM ET (US) For all you experienced performance guys: Consider a 1998 Outrage 20 (2,200-lbs hull), with 2000 FICHT RAM 225 (506-lbs) and 15-1/4" x 19" MIRAGEplus propeller; 30- gallons of fuel, three people, no big coolers of ice, no T-Top, and a bimini Will this boat exceed 3-MPG at 25- to 30-MPH cruise?
an86carrera	posted 05-24-2009 07:39 AM ET (US) I have a 200 ficht on a 22' with a T-top and get 3mpg. So you might. Len
Peter	posted 05-24-2009 08:48 AM ET (US) Should be acheivable. With a 19 inch pitch propeller, you should be able to see 30 MPH at about 3500 RPM. At 3500 RPM, your Ficht should be burning approximately 8 GPH.
jimh	posted 05-24-2009 09:55 AM ET (US) To get 3-MPG at 25-MPH the fuel burn rate has to be 1-gallon/3-miles X 25-miles/1-hour = 8.33-GPH We now consider how much horsepower the FICHT motor can produce with 8.33-GPH fuel burn. For this we need to know the brake specific fuel consumption of the motor. We estimate this to be about 0.5-lbs/HP-Hour 8.33-Gallons/1-hour x 6.25-lbs/1-gallon = 52-lbs/Hour 52-lbs/1-hour x 1-HP-Hour/0.5-lbs = 104-HP Can 104-HP move the boat at 25-MPH? Now we turn to Crouch's Calculator. According to Crouch, if we figure the HULL FACTOR =180, with 104-HP we can go 25-MPH with a total weight of as much as 5,391-lbs. The estimated weight of the OUTRAGE 20 can be calculated as follows: HULL = 2,200 MOTOR = 510 PROPELLER =15 FUEL = 200 CREW = 700 MISC = 700 TOTAL = 4,325 Since the total weight of 4,325-lbs is less than Crouch's calculated weight, we should be able to reach 25-MPH with less than 104-HP. If our estimate of the brake specific fuel consumption was accurate, then we will hit our fuel economy target of 3-MPG.
jimh	posted 05-24-2009 09:59 AM ET (US) By the way, my analysis is not based on experience. It is based on an understanding of the principles of naval architecture and conversion of fuel to power.
jimh	posted 05-24-2009 10:27 AM ET (US) In a prior discussion http://continuouswave.com/ubb/Forum4/HTML/004149.html some observed data about the BSFC of a FICHT engine was given. The BSFC was estimated at about 0.57-lbs/HP-Hour. Let's revisit the problem with that number: Target fuel burn rate is 8.33-GPH BSFC is 0.57-lbs/HP-Hour Horsepower is then 8.33-Gallons/1-hour x 6.25-lbs/1-gallon x 1-HP-Hour/0.57-lbs = 91-HP Maximum weight for HULL FACTOR = 180 HP = 91 MPH =25 calculates to 4,717-lbs. This is still greater than our estimated total weight for the boat, so we should still be able to reach the target fuel economy.
jimh	posted 05-24-2009 10:36 AM ET (US) Let's try this again at the upper speed range of 30-MPH. Our fuel burn rate will be 10-GPH. This allows the horsepower to be 110-HP. Crouch says maximum weight has decreased to only 3,960-lbs. This means our OUTRAGE 20 total weight probably will exceed this figure. Thus the fuel economy at 30-MPH will likely not reach 3-MPG. The outcome in the real world will depend on the nature of the hull and where it really likes to run for optimum efficiency. It has been my observation--now I am using my experience--that for Boston Whaler boats in the 20-foot to 22-foot range there will generally be a speed in the range of 24-MPH to 28-MPH where the boat will produce the best fuel economy. The outcome depends a great deal on how the boat is set up, and particularly the propeller being used. I suspect that with a 1998 OUTRAGE 20 there will very likely be a particular speed where you can hit a fuel economy of 3-MPG in the 25- to 30-MPH range.
acseatsri	posted 05-24-2009 12:11 PM ET (US) My Outrage 22 with E-TEC 225, T-top, full fuel, and 3 people aboard gets over 3-MPG anywhere from 18 to 35-MPH, with best economy (3.3-MPG) between 24 to 28-MPH. Jim's numbers are spot on.
Smithsm	posted 05-24-2009 04:13 PM ET (US) If I understand this correctly - my take on the calculation USING MY WEIGHT ASSUMPTIONS, I will be able to get 3 mpg at 30 mph because I see the total weight as less. here is my weight estimate: HULL = 2,200 MOTOR = 510 PROPELLER =15 FUEL = 200 Batteries - 110 CREW = 545 (230, 115, 200) Tackle Box = 20 MISC = 200 TOTAL = 3,800 while crouch says we could do 3960 pounds at 10 gph at 30 mph this all means I am optmimistic that I will get the results mentioned by acseatsri.... acseatsri posted 05-24-2009 12:11 PM ET (US) -------------------------------------------------------------------------------- My Outrage 22 with E-TEC 225, T-top, full fuel, and 3 people aboard gets over 3-MPG anywhere from 18 to 35-MPH, with best economy (3.3-MPG) between 24 to 28-MPH. Jim's numbers are spot on.
acseatsri	posted 05-24-2009 06:56 PM ET (US) If you are using 3 MPG as a figure to determine offshore range, I would use 2 MPG as the divisor. If plowing thru heavy seas, I often have to pull it back to 12 MPH with the tabs fully extended, which gets me 6 GPH for a net of 2 MPG, worst case scenario.
phatwhaler	posted 05-24-2009 07:01 PM ET (US) You ought to be able to exceed 3mpg easily with a Ficht. My 200 Merc with carbs will give me a hair over 3mpg at cruise. I have a T-top also.
Smithsm	posted 05-24-2009 07:11 PM ET (US) [Could we start using that SHIFT KEY to capitalize the intial letter of the initial word of each sentence, please?--jimh] [A]n interesting theoretical question (at least for me) is how the [fuel economy] might be expected to change were the boat powered by a lighter 175- or 150-HP engine. [T]he engine would no doubt spin a less agressive prop fast to get to the 24-28 mph hull sweet spot but would there really be any fuel savings by using the lower displacement engine? [I]f I understand JimH's models, I don't see exactly what variable, other than lower engine weight of 80 pounds would change; therefore the [fuel economy] may not be improved via a smaller engine on the 20-foot boat. [A]m I missing something or is MPG relatively independent of the horsepower on the outboard so long as the combustion efficiency is similar?
jimh	posted 05-24-2009 07:24 PM ET (US) You're into a whole new arena of speculation when you want to discuss engine efficiency as a function of engine displacement. If you really want to go there, start a new thread. As for the extra 700-lbs I assigned to your weight estimate, that is based on my experience. Boats always weigh more than you think. For example, you did not allow for the batteries, the anchor, the oil tanks, the usual gear you'll have on board, and other "stuff." It all adds up. The only way to really know how much the boat weighs is to take it to a scale.