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01-07-2019, 14:13
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#46
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Cost per hour of running engine
Quote:
Originally Posted by valhalla360
Certainly you can calculate based on either but MPG is more direct in terms of efficiency rating.
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Sure it is, but without knowing burn rate, how do you calculate MPG?
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01-07-2019, 14:37
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#47
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Registered User
Join Date: Mar 2013
Location: San Diego
Boat: Jeanneau 349, FP 47, Sense 50, J 42ds
Posts: 752
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Re: Cost per hour of running engine
It is easy to get your burn rate. The manufacturers all pretty much publish fuel versus rpm graphs. I print up and laminate a card showing flat water speed for each rpm. I find my actual speed at an rpm varies greatly with sea conditions. Whereas I motor at 8 knots at 2500 rpm in flat water, I average 5.5 knots at the same rpm pounding up the coast of Baja. At least, by watching my engine hours I know how much fuel I've burned.
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01-07-2019, 14:52
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#48
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Cost per hour of running engine
The manufacturers charts will get you close, some awfully close if your boat is propped exactly correct, mine for example is a little overpropped, so I will burn more fuel that the charts says, cause I’m making slightly more power than it should at that RPM.
I got there over time, burning fuel, knowing how many hours and how many gallons to fill back up. I think I’m pretty close now.
Two things amaze me about my fuel gauge, first it’s Circa 1987 and it works, secondly it’s awfully accurate but I think maybe that is because my tank is straight walled too.
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01-07-2019, 14:58
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#49
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Cost per hour of running engine
Quote:
Originally Posted by Zzmeyer
I find my actual speed at an rpm varies greatly with sea conditions.
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Mine varies too, but my burn rate per RPM is a constant, but as the speed varies, it’s easy to compute MPG and therefore range. My boat beating directly into the wind really slows down, and range of course drops with the speed.
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01-07-2019, 15:04
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#50
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Registered User
Join Date: Mar 2013
Location: San Diego
Boat: Jeanneau 349, FP 47, Sense 50, J 42ds
Posts: 752
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Re: Cost per hour of running engine
a64pilot. Exactly. My fuel gauge is accurate, too. It's just where the needle points that is way off. I've actually calibrated fairly accurately (1/2 tank says 3/4, 3/4 tank says full). As you have said, fuel consumption is constant at a constant rpm so if you are motoring a long distance at a constant rpm you can calculate the number of hours of engine run time you'll get. I motor each spring from Cabo San Lucas to San Diego, a distance of 750 miles and I find my speed varies so much over the week or so that calculating range is problematic. I'll generally pick up 50 gallons in Turtle Bay to be safe, but my 220 gallon capacity would probably get me home.
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01-07-2019, 15:15
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#51
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Senior Cruiser
Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 12,159
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Re: Cost per hour of running engine
I know at 1800rpm which is my best speed vs burn for my boat I burn .4 gph I carry 23 gallons so that means I carry 57 hours worth of fuel . I can estimate range from that depending on GPS SOG which is constantly variable but on any given passage I can estimate my available fuel distance quite close . ( never more than 40 hours time ) but a sailboat I doubt I will burn half that in 2 years .
Most of my fuel burn is my furnace in winter at a half gallon per day +/-
__________________
Non illigitamus carborundum
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01-07-2019, 15:18
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#52
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Registered User
Join Date: Apr 2012
Location: Winter Germany, Summer Med
Boat: Lagoon 380 S2
Posts: 1,923
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Re: Cost per hour of running engine
Quote:
Originally Posted by Kenomac
Our cost is less than half for a 100hp turbo. Fuel burn 4 liters per hour at .62 cents per liter. Oil change once per season done ourselves and fuel filter once every couple of years by self when needed, which is rare because fuel is polished regularly onboard.
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I thought you were in Europe? Where do you steal diesel at .62ct/liter ?
Normal boat fuel dock in Italy is more like 3x as much.
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01-07-2019, 17:39
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#53
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Cost per hour of running engine
Quote:
Originally Posted by Zzmeyer
a64pilot. Exactly. My fuel gauge is accurate, too. It's just where the needle points that is way off. I've actually calibrated fairly accurately (1/2 tank says 3/4, 3/4 tank says full). As you have said, fuel consumption is constant at a constant rpm so if you are motoring a long distance at a constant rpm you can calculate the number of hours of engine run time you'll get. I motor each spring from Cabo San Lucas to San Diego, a distance of 750 miles and I find my speed varies so much over the week or so that calculating range is problematic. I'll generally pick up 50 gallons in Turtle Bay to be safe, but my 220 gallon capacity would probably get me home.
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Old aviation expression “Only time you can have too much fuel is if your on fire”
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01-07-2019, 17:58
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#54
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Registered User
Join Date: Feb 2013
Location: Oregon
Boat: Seafarer36c
Posts: 5,563
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Re: Cost per hour of running engine
Quote:
Originally Posted by a64pilot
Old aviation expression “Only time you can have too much fuel is if your on fire”
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Makes me think of Lindbergh or Rutan on take off.
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01-07-2019, 18:28
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#55
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Cost per hour of running engine
Quote:
Originally Posted by Ecos
Makes me think of Lindbergh or Rutan on take off.
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They both made it though didn’t they?
Lindbergh’s problem was with the mud, he had computed take off distance for a dry runway, but didn’t have one of course.
Rutan’s was aircraft design / pilot error as speed built up the wing tips were pushed down as they had a negative angle of attack when on the ground,Dick Rutan wanted a little extra speed, which was understandable because the aircraft had never flown at a anything even near that weight before rotating, and waited just a little too long.
Both are I think perfect examples of why you need a little fudge, because sometimes things don’t go as planned, Murphy has a vote too.
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05-07-2019, 06:46
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#56
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Registered User
Join Date: Nov 2016
Posts: 13
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Re: Cost per hour of running engine
Don’t forget if you’re sailing about 1/2 the time the engine is off and the rest of the time hopefully you’re motor sailing and adding some Drive with the wind. We are often cruising at 4 knots. Keeping the old Perkins slow and quiet, overall average including wind propulsion 10 nmpg. Might consider cost per mile? Also I guess you’d have to throw all those sail related expenses into the equation plus all the other repairs if you’re long time cruising. Living on the hook?
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05-07-2019, 06:51
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#57
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Registered User
Join Date: Mar 2018
Posts: 5
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Re: Cost per hour of running engine
But are you having fun for that hour? You could be sitting at home and staring at the walls. Hey what ever the cost, we all have a need to get out on the water and counting pennies to this detail is for tug boat and fisherman where costs matter. We all have a bar code on our neck and we can not see the expiry date.
Get out and have some fun!
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05-07-2019, 08:53
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#58
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Registered User
Join Date: Nov 2018
Location: NJ
Boat: Mariner 38 Pilot House
Posts: 186
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Re: Cost per hour of running engine
Quote:
Originally Posted by kev_rm
I figured USD$4/gallon.. which I think is an OK average but I am still a little surprised by the low gph figures. Your boats get 10mpg + ??
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My 4108 burns about .6 gallons per hour @2200rpm. That pushes my 38' boat along at 6.5 knots. So without tide or headwinds I can achieve 7.48 mpg. Came down the Hudson the other day with the tide doing 8-10 knots SOG @2000rpm so I was likely getting 12-14mpg.
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05-07-2019, 09:32
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#59
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Registered User
Join Date: Apr 2010
Location: Western MA & Maine
Boat: 1997 Sabre 362
Posts: 67
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Re: Cost per hour of running engine
Some years ago, when I bought my first boat, a friend told me to keep a detailed spreadsheet of my gear & maintenance costs but never ever total it.
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05-07-2019, 13:40
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#60
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Registered User
Join Date: May 2014
Location: British Colombia Canada
Boat: Corbin 39
Posts: 37
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Re: Cost per hour of running engine
Quote:
Originally Posted by kev_rm
Assuming something in the 30-50hp range, I am coming up with about US$13/hour, any comments?
Fuel GPH 1.5
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We ran a Perkins Prima 50 and our fuel consumption 2.4 Liters/hour
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