Offshore 27 Estimated Fuel Consumption - Moderated Discussion Areas

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: Whaler Performance
  Offshore 27 Estimated Fuel Consumption

search | FAQ | profile | register | author help

Author Topic:   Offshore 27 Estimated Fuel Consumption

TallyHo posted 08-22-2012 12:44 PM ET (US)
[What are the] statistics on fuel burn on a Offshore 27? I am trying to get an idea of a best and worst case scenario on fuel burn for these boats. Thx.
Plotman posted 08-22-2012 01:45 PM ET (US)
I looked at buying one a couple of years ago. With conventional 2 strokes, you were just over 1-MPG at 30-MPH cruise.
contender posted 08-22-2012 04:00 PM ET (US)
If you can afford a 27 Whaler, then you better not be worried about fuel cost, because then you can not afford a 27 Whaler.
Jeff posted 08-22-2012 04:43 PM ET (US)
If I remember correctly, "Oyster" has a Offshore 27 with twin 250 E-Tec's and reported a cruise in the mid to upper 20-MPH range and [the MPG was] in the high two to around three range. Jason (contender25) reported a regular 1.3-MPG burn rate at the same speeds with his Offshore 27 running early 1990's 225 Johnson Ocean Runners
Peter posted 08-22-2012 05:19 PM ET (US)
Set up right, you can figure about an 18 GPH burn rate at 30 MPH with either 4-strokes or DFI 2-strokes 225 or 250s. 2-stroke motors will be turning about 3750 RPM, 4-strokes about 4000-4200 RPM.
TallyHo posted 08-22-2012 06:31 PM ET (US)
Thanks all, appreciate the responses. [The fuel consumption is lower than I] thought really. Pretty funny though, when I wrote this i knew I would get the inevitable "you should ask with this boat" comments. However, I have a boat that gets 0.75-MPG at times, and to me, 1.3-MPG is a strong increase in fuel economy--makes a difference when you use them more then once a year like I do.
jimh posted 08-22-2012 09:07 PM ET (US)
Let's estimate the weight of an OFFSHORE 27 to be about 8,000-lbs ready to go. We want to cruise at 27-MPH. We will need to calculate the horsepower. Using CROUCH'S CALCULATOR, I figure 180-HP. See
http://continuouswave.com/cgi-bin/crouchcalc.pl
If we have twin engines of modern design we can figure the BSFC will be about 0.45-lbs/HP-hour. To make 180-HP we will need to burn
0.45-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 13-GPH
If we burn 13-GPH and are going 27-MPH, then our fuel economy will be
1-hour/13-gallons x 27-miles/1-hour = 2.1-MPG
If we use older engines the BSFC will be more like 0.55-lbs/HP-hour. The fuel burn will be
0.55-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 15.8-GPH
and the fuel economy will be
1-hour/15.8-gallons x 27-miles/1-hour =1.7-MPG
If we have really old engines and their BSFC is about 0.62, the fuel burn will be
0.62-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 17.8-GPH
and the fuel economy will be down around
1-hour/17.8-gallons x 27-miles/1-hour =1.5-MPG
I don't know if you can hit these numbers, as you may be losing a bit with the twin engines having more drag.
contender posted 08-22-2012 09:48 PM ET (US)
TallyHo: I was not being mean, but really if you are worried about fuel issues you can not afford the boat. The boat will be sitting on the side of your house or in a marina or even in a covered garage not being use, because of the fuel is to expensive...
TallyHo posted 08-22-2012 10:25 PM ET (US)
No worries, contender, didnt think you were being mean, i just knew that was coming. My point about fuel cost is simply related to economics of scale.
When relating it to boats, one can only compare similar options in the same size category. I love the offshore 27 but if that boat gets 40% worse fuel economy than a similar boat, well that needs to be considered. Make sense?
My friend contests that these hulls are "pigs"(compared to others in this range) and are notorious for consuming large amounts of fuel, i guess thats what i was asking.
Thanks for everyones thoughts, this site has been a great resource for me as a fellow Whaler freak.
-TH
PeteB88 posted 08-22-2012 11:39 PM ET (US)
Are the hulls really pigs? regarding fuel consumption? ?
contender posted 08-23-2012 07:54 AM ET (US)
Tally: understand your thinking, Yes, you will get better mileage with other hulls designs, the whalers are just pushing to much water, and are (pigs in that sense). I feel after 25 ft its better to look at different hulls for fuel consumption. After 30 ft I wold be looking at inboard diesels. Just that you are going to need a dock/marina to keep it a hull that size...Good luck to you
Peter posted 08-23-2012 08:13 AM ET (US)
The classic era Whaler hulls designed in the 1970s or early 1980s are not as fuel efficient as a hull designed in the 2000s. The size of the Whaler hull does not matter. The hull design with twin sponsons which provide stability and incredibly straight tracking in all sea states require more energy to drag through the water than a more conventionally designed V hull with similar deadrise.
I an not aware of any other 27 foot boat offered either at the time the Offshore was made or after that was unsinkable, offered a 10,000 lb swamped capacity rating and provided a super dry ride. In fact, its quite rare to find a 27 foot outboard powered boat with a 10 foot beam offering a huge cockpit as the 27 foot Whaler did in addition to the superior tracking. If you want all that, then you have to pay the price. Every boat is a compromise of one thing for another.
I doubt that the fuel economy of the 27 Offshore at its most efficient cruise speed will be better than 1.8 MPG. Of course with modern motors very fuel efficient motors such as DFI 2-strokes with stratified fuel charging, the economy will be in the 5 MPG range or better while slow trolling.
jimh posted 08-23-2012 09:15 AM ET (US)
For me the OFFSHORE 27 has always been my favorite Boston Whaler boat. I think it is a beautiful design. If you can get 1.8-MPG with that boat with modern engines that is wonderful. I bought a lot of fuel for my 22-footer when it was averaging 1.75-MPG and running a carburetor two-cycle outboard. Why wouldn't I buy the same (or less) fuel to run around in an OFFSHORE 27 with modern outboard engines?
TallyHo posted 08-23-2012 04:56 PM ET (US)
Jimh, I completely agree with everything you said! I, of course, would throw in a Outrage 18 in as well!
Peter, you point is very well taken; "overall" daily consumption numbers are very important to me. I often fish a outrage 18, 30+ miles off the Oregon Coast for Albacore and average 4+ nmpg a day. Thats just phenomenal to me.
A offshore 27 that gets a average for a day around 1.5 would be phenomenal to me as well for a boat like that.

ericflys posted 08-23-2012 06:19 PM ET (US)
Peter, did you mean 5 GPH for slow trolling?
TallyHo, for what it's worth, I get about 5.7-5.9 MPG (at 25 MPH)and drops to about 5.3-5.4 MPG at 30 MPH, out of my Outrage 18, which I think is remarkable as my buddy's Montauk 17 with a Honda 90 gets much worse economy. I don't know what other brands of 18.5 foot boats get for fuel economy with like engines, but I think it would be hard to beat the Outrage 18, without significantly reducing weight and making a lot of other sacrifices.
Peter posted 08-23-2012 08:32 PM ET (US)
Eric - 5+ mpg at slow troll. Two 225s turning 17 inch pitch propellers in gear will push the boat to 3.7 mph while burning 0.6 GPH. One motor will get 3 mph on 0.3 gph. On an Offshore 27 those motors might be able to turn 19 inch pitch so speed would go up to 4 mph for both motors on same miserly fuel burn rate.
TH - With stratified charged DFI 2-strokes, worst mpg will be at cruise so your average mpg will be higher than the cruise mpg.
jimh posted 08-24-2012 09:16 AM ET (US)
The low fuel consumption of a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control--don't want to mention any special brand here or we will get into a bunch of silly brand war comments--will be very low. My 225-HP modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control can run at idle speeds and consume only 0.2-gallons-per-hour. At idle speed the boat is pushed to about 3-MPH, which might be a great speed for trolling.
The implication of fuel consumption at 0.2-GPH is that you can troll for five hours and only burn a gallon of fuel. If your boat use pattern is to run offshore for an hour, then troll for many hours, a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control can significantly reduce your fuel consumption.
Even if you want to move faster, say 6-MPH, the fuel burn will remain below 1-GPH. You can troll for five hours on perhaps four-gallons of fuel. I am sure that will be a welcome reduction in fuel consumption.
Again, you just need to re-power with a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control to get this sort of fuel economy.
Peter posted 08-24-2012 09:48 AM ET (US)
Another advantage of DFI 2-stroke at trolling speeds is extremely low oil consumption and no crankcase oil dilution from cool powerhead temperatures at troll speeds.
jimh posted 08-25-2012 10:59 AM ET (US)
Peter has a good point. If you pile up engine hours at idle speed on a four-cycle outboard engine, you will require an oil change more frequently. With a two-cycle engine that idles nicely and has low oil and fuel consumption, you will not have to change the oil.
martyn1075 posted 08-27-2012 11:55 PM ET (US)
The problem with that theory is that most two stroke engines not mentioning brands dont like to be run at idol speeds for two long. This is exactly why most people who want to cruise at low rpm's will go with a four stroke even though as mentioned already they require more oil changes. How about using modern two stroke engine and use a four stroke kicker for everything else.
Peter posted 08-28-2012 07:43 AM ET (US)
The brand of my former DFI 2-strokes had no problem running at idle speed for extended periods.
martyn1075 posted 08-28-2012 03:39 PM ET (US)
I know Peter but we don't want to get into the brands and most of us know what you had on there which is not a bad thing they were probably trouble free. The two stroke technology in general are not usually good at idle speeds for long periods of time.
Martyn
Peter posted 08-28-2012 09:26 PM ET (US)
I don't understand what is included in "two stroke technology in general" or most two stroke engines. Does that include or exclude carb'd 2-strokes?
Tom W Clark posted 09-04-2012 10:20 AM ET (US)

quote:
...most two stroke engines not mentioning brands dont like to be run at idol speeds for two long.
That is utter hogwash.

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: Offshore 27 Estimated Fuel Consumption
TallyHo	posted 08-22-2012 12:44 PM ET (US) [What are the] statistics on fuel burn on a Offshore 27? I am trying to get an idea of a best and worst case scenario on fuel burn for these boats. Thx.
Plotman	posted 08-22-2012 01:45 PM ET (US) I looked at buying one a couple of years ago. With conventional 2 strokes, you were just over 1-MPG at 30-MPH cruise.
contender	posted 08-22-2012 04:00 PM ET (US) If you can afford a 27 Whaler, then you better not be worried about fuel cost, because then you can not afford a 27 Whaler.
Jeff	posted 08-22-2012 04:43 PM ET (US) If I remember correctly, "Oyster" has a Offshore 27 with twin 250 E-Tec's and reported a cruise in the mid to upper 20-MPH range and [the MPG was] in the high two to around three range. Jason (contender25) reported a regular 1.3-MPG burn rate at the same speeds with his Offshore 27 running early 1990's 225 Johnson Ocean Runners
Peter	posted 08-22-2012 05:19 PM ET (US) Set up right, you can figure about an 18 GPH burn rate at 30 MPH with either 4-strokes or DFI 2-strokes 225 or 250s. 2-stroke motors will be turning about 3750 RPM, 4-strokes about 4000-4200 RPM.
TallyHo	posted 08-22-2012 06:31 PM ET (US) Thanks all, appreciate the responses. [The fuel consumption is lower than I] thought really. Pretty funny though, when I wrote this i knew I would get the inevitable "you should ask with this boat" comments. However, I have a boat that gets 0.75-MPG at times, and to me, 1.3-MPG is a strong increase in fuel economy--makes a difference when you use them more then once a year like I do.
jimh	posted 08-22-2012 09:07 PM ET (US) Let's estimate the weight of an OFFSHORE 27 to be about 8,000-lbs ready to go. We want to cruise at 27-MPH. We will need to calculate the horsepower. Using CROUCH'S CALCULATOR, I figure 180-HP. See http://continuouswave.com/cgi-bin/crouchcalc.pl If we have twin engines of modern design we can figure the BSFC will be about 0.45-lbs/HP-hour. To make 180-HP we will need to burn 0.45-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 13-GPH If we burn 13-GPH and are going 27-MPH, then our fuel economy will be 1-hour/13-gallons x 27-miles/1-hour = 2.1-MPG If we use older engines the BSFC will be more like 0.55-lbs/HP-hour. The fuel burn will be 0.55-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 15.8-GPH and the fuel economy will be 1-hour/15.8-gallons x 27-miles/1-hour =1.7-MPG If we have really old engines and their BSFC is about 0.62, the fuel burn will be 0.62-lbs/1-HP-hour x 1-hour x 180-HP x 1-gal/6.25-lbs = 17.8-GPH and the fuel economy will be down around 1-hour/17.8-gallons x 27-miles/1-hour =1.5-MPG I don't know if you can hit these numbers, as you may be losing a bit with the twin engines having more drag.
contender	posted 08-22-2012 09:48 PM ET (US) TallyHo: I was not being mean, but really if you are worried about fuel issues you can not afford the boat. The boat will be sitting on the side of your house or in a marina or even in a covered garage not being use, because of the fuel is to expensive...
TallyHo	posted 08-22-2012 10:25 PM ET (US) No worries, contender, didnt think you were being mean, i just knew that was coming. My point about fuel cost is simply related to economics of scale. When relating it to boats, one can only compare similar options in the same size category. I love the offshore 27 but if that boat gets 40% worse fuel economy than a similar boat, well that needs to be considered. Make sense? My friend contests that these hulls are "pigs"(compared to others in this range) and are notorious for consuming large amounts of fuel, i guess thats what i was asking. Thanks for everyones thoughts, this site has been a great resource for me as a fellow Whaler freak. -TH
PeteB88	posted 08-22-2012 11:39 PM ET (US) Are the hulls really pigs? regarding fuel consumption? ?
contender	posted 08-23-2012 07:54 AM ET (US) Tally: understand your thinking, Yes, you will get better mileage with other hulls designs, the whalers are just pushing to much water, and are (pigs in that sense). I feel after 25 ft its better to look at different hulls for fuel consumption. After 30 ft I wold be looking at inboard diesels. Just that you are going to need a dock/marina to keep it a hull that size...Good luck to you
Peter	posted 08-23-2012 08:13 AM ET (US) The classic era Whaler hulls designed in the 1970s or early 1980s are not as fuel efficient as a hull designed in the 2000s. The size of the Whaler hull does not matter. The hull design with twin sponsons which provide stability and incredibly straight tracking in all sea states require more energy to drag through the water than a more conventionally designed V hull with similar deadrise. I an not aware of any other 27 foot boat offered either at the time the Offshore was made or after that was unsinkable, offered a 10,000 lb swamped capacity rating and provided a super dry ride. In fact, its quite rare to find a 27 foot outboard powered boat with a 10 foot beam offering a huge cockpit as the 27 foot Whaler did in addition to the superior tracking. If you want all that, then you have to pay the price. Every boat is a compromise of one thing for another. I doubt that the fuel economy of the 27 Offshore at its most efficient cruise speed will be better than 1.8 MPG. Of course with modern motors very fuel efficient motors such as DFI 2-strokes with stratified fuel charging, the economy will be in the 5 MPG range or better while slow trolling.
jimh	posted 08-23-2012 09:15 AM ET (US) For me the OFFSHORE 27 has always been my favorite Boston Whaler boat. I think it is a beautiful design. If you can get 1.8-MPG with that boat with modern engines that is wonderful. I bought a lot of fuel for my 22-footer when it was averaging 1.75-MPG and running a carburetor two-cycle outboard. Why wouldn't I buy the same (or less) fuel to run around in an OFFSHORE 27 with modern outboard engines?
TallyHo	posted 08-23-2012 04:56 PM ET (US) Jimh, I completely agree with everything you said! I, of course, would throw in a Outrage 18 in as well! Peter, you point is very well taken; "overall" daily consumption numbers are very important to me. I often fish a outrage 18, 30+ miles off the Oregon Coast for Albacore and average 4+ nmpg a day. Thats just phenomenal to me. A offshore 27 that gets a average for a day around 1.5 would be phenomenal to me as well for a boat like that.
ericflys	posted 08-23-2012 06:19 PM ET (US) Peter, did you mean 5 GPH for slow trolling? TallyHo, for what it's worth, I get about 5.7-5.9 MPG (at 25 MPH)and drops to about 5.3-5.4 MPG at 30 MPH, out of my Outrage 18, which I think is remarkable as my buddy's Montauk 17 with a Honda 90 gets much worse economy. I don't know what other brands of 18.5 foot boats get for fuel economy with like engines, but I think it would be hard to beat the Outrage 18, without significantly reducing weight and making a lot of other sacrifices.
Peter	posted 08-23-2012 08:32 PM ET (US) Eric - 5+ mpg at slow troll. Two 225s turning 17 inch pitch propellers in gear will push the boat to 3.7 mph while burning 0.6 GPH. One motor will get 3 mph on 0.3 gph. On an Offshore 27 those motors might be able to turn 19 inch pitch so speed would go up to 4 mph for both motors on same miserly fuel burn rate. TH - With stratified charged DFI 2-strokes, worst mpg will be at cruise so your average mpg will be higher than the cruise mpg.
jimh	posted 08-24-2012 09:16 AM ET (US) The low fuel consumption of a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control--don't want to mention any special brand here or we will get into a bunch of silly brand war comments--will be very low. My 225-HP modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control can run at idle speeds and consume only 0.2-gallons-per-hour. At idle speed the boat is pushed to about 3-MPH, which might be a great speed for trolling. The implication of fuel consumption at 0.2-GPH is that you can troll for five hours and only burn a gallon of fuel. If your boat use pattern is to run offshore for an hour, then troll for many hours, a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control can significantly reduce your fuel consumption. Even if you want to move faster, say 6-MPH, the fuel burn will remain below 1-GPH. You can troll for five hours on perhaps four-gallons of fuel. I am sure that will be a welcome reduction in fuel consumption. Again, you just need to re-power with a modern outboard engine using a stratified charge method and direct fuel injection coupled with precise computer control to get this sort of fuel economy.
Peter	posted 08-24-2012 09:48 AM ET (US) Another advantage of DFI 2-stroke at trolling speeds is extremely low oil consumption and no crankcase oil dilution from cool powerhead temperatures at troll speeds.
jimh	posted 08-25-2012 10:59 AM ET (US) Peter has a good point. If you pile up engine hours at idle speed on a four-cycle outboard engine, you will require an oil change more frequently. With a two-cycle engine that idles nicely and has low oil and fuel consumption, you will not have to change the oil.
martyn1075	posted 08-27-2012 11:55 PM ET (US) The problem with that theory is that most two stroke engines not mentioning brands dont like to be run at idol speeds for two long. This is exactly why most people who want to cruise at low rpm's will go with a four stroke even though as mentioned already they require more oil changes. How about using modern two stroke engine and use a four stroke kicker for everything else.
Peter	posted 08-28-2012 07:43 AM ET (US) The brand of my former DFI 2-strokes had no problem running at idle speed for extended periods.
martyn1075	posted 08-28-2012 03:39 PM ET (US) I know Peter but we don't want to get into the brands and most of us know what you had on there which is not a bad thing they were probably trouble free. The two stroke technology in general are not usually good at idle speeds for long periods of time. Martyn
Peter	posted 08-28-2012 09:26 PM ET (US) I don't understand what is included in "two stroke technology in general" or most two stroke engines. Does that include or exclude carb'd 2-strokes?
Tom W Clark	posted 09-04-2012 10:20 AM ET (US) quote: ...most two stroke engines not mentioning brands dont like to be run at idol speeds for two long. That is utter hogwash.