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Old 12-04-2014, 10:29 AM   #41
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Actually I use nmpg. But that is hairsplitting . We could use gallons per furlong as well .My point is that people are far more familiar with mpg than gph and discussions in mpg of either sort are more meaningful to many.
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Old 12-04-2014, 11:37 AM   #42
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MPG, NMPG, GPH - wow what a conundrum. Now that I am thoroughly confused I'll top my tanks when they get to between 25 to 30% fuel remaining. Unless of course I am at an el cheapo place that beats the price 200 miles or so up the line.

Or better yet, $ per mile which then gives one the opportunity to travel less if you're really a penny pincher. AKA a dock queen. They're everywhere. Notice how most of your slip neighbors seem to never go anywhere, do they have this conundrum figured out?
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Old 12-04-2014, 09:42 PM   #43
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Data

I understand the advice on all the other costs involved in boating and I am still analyzing it. thought provoking, thanks I am a numbers guy, so thanks for all the data. It helps in deciding, so I don't buy too big or too much HP. I am surprised that a 39,000# full displacement can get better mileage (at the same speed) than a 22,000# semi. displacement. I guess I will stay away from semi planing or planning hulls. Thanks Steve.
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Old 12-04-2014, 10:30 PM   #44
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Originally Posted by SteveandZoila View Post
I understand the advice on all the other costs involved in boating and I am still analyzing it. thought provoking, thanks I am a numbers guy, so thanks for all the data. It helps in deciding, so I don't buy too big or too much HP. I am surprised that a 39,000# full displacement can get better mileage (at the same speed) than a 22,000# semi. displacement. I guess I will stay away from semi planing or planning hulls. Thanks Steve.
Just to throw a little more wood on the fire. The type of hull when making comparisons between semi and full displacement boats of similar length is not always the major factor in fuel burn. The engine size and stern gear- the waterline length -overall weight -freeboard and wind age-beam and nature of the hull entry fineness also have to be taken into account. Two 50 footers one semi and the other full displacement could have identical fuel burns at seven or eight knots or either could be better depending on factors other than hull type. Often the choices made in setting up the semi include the option of speeds above hull speed and the use of big twins thus a loss in economy, but nothing says a SD cant be set up for good fuel burn . So a lighter modest size single engine semi-displacement boat with a set up for good fuel burn can out-shine a heavier FD boat both traveling one knot below hull speed.
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Old 12-09-2014, 10:46 AM   #45
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Actually real time consumption is the way I often set my cruise speed. I set my rpm where I burn a total of 5 gallons per hour. This is not my most economical speed but is a compromise related to various comfort factors. Since this is done in the PNW the GPS speed may vary between 5 and 14 knots while the speed through the water is usually pegged at about 9.2K which is about my calculated hull speed. Attempts to go faster cause the fuel burn curve to rise steeply.
Maybe this is a stupid question, but isn't that normal, to set rpms?
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