"I find that with wide open throttle my 20hp mariner 4 stroke burns about 4 gallons an hour, a lot more than I expected." Paige: How fast are you going at WOT? Larry/Lena Hobo KK42 La Paz, BCS, MX

Hi Adam, I've been racking my brains trying to remember why I thought my outboard was consuming too much fuel. Then I found a copy of this article in my files http://www.boatingmag.com/skills/calculating-fuel-consumption Consumption should be around 0.4 to 0.45 pounds weight of fuel per horse power. Given the worst figure, on this scale your outboard would consume around eleven and a quarter pounds of fuel per hour at WOT. A US gallon of gasoline weighs around 6.25 lbs, so I'd estimate with your twenty gallons you'd have 10 hours if you use it wide open all the time. I must get someone to tune mine, seems like I'm wasting a lot of fuel. Paige

Paige, that's a fascinating datum and exactly what I was looking for. I actually have a 10 or 11 gallon tank (reports vary) so it's more like 5.5 hours. If my planing speed is 15 knots (I don't know, because the pitot tube speedo doesn't work), that equates to a mileage of about 8 nmpg. That's quite good, especially as my modern fuel injected outboard should do better than the worst-case 0.45 gph. It's interesting to do this calculation for the electronically controlled Lugger 1066T in our Nordhavn. At WOT (170 hp), we consume 9 gph, or 63.9 lbs (with diesel denser than gas at 7.1 lbs per gal). Dividing that figure into 170 hp you get 0.38 gal per hp per hour, right in line with the figures you cited. Thanks!!! /afb On Sep 27, 2010, at 22:13, Paige <paige.reeves99@yahoo.co.uk> wrote: > Hi Adam, > > > I've been racking my brains trying to remember why I thought my outboard was consuming too much fuel. Then I found a copy of this article in my files http://www.boatingmag.com/skills/calculating-fuel-consumption > > Consumption should be around 0.4 to 0.45 pounds weight of fuel per horse power. Given the worst figure, on this scale your outboard would consume around eleven and a quarter pounds of fuel per hour at WOT. A US gallon of gasoline weighs around 6.25 lbs, so I'd estimate with your twenty gallons you'd have 10 hours if you use it wide open all the time. > > > I must get someone to tune mine, seems like I'm wasting a lot of fuel. > > Paige > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/trawlers-and-trawlering > > To unsubscribe or modify your subscription options (get password, change email address, etc) go to: http://lists.samurai.com/mailman/options/trawlers-and-trawlering > > Trawlers & Trawlering and T&T are trademarks of Water World > Productions. Unauthorized use is prohibited.