Diesel fuel consumption?

[Franklin]

hmmm

"with several good folks telling us more than they actually know."I remember hearing this someplace before....hmmm....I could really go off now but I'll just stick to the facts. Fact is Bert, that if your moving in the water, that provides less resistance on the prop then if your sitting still. That resistance effects the load on the engine. The more the resistance, the more fuel it takes to reach the RPM at question. Now lets say your trying to motor against a 30 knot wind. Your not going to be moving much. That lack of speed through the water will provide more resistance on the spinning of the prop (not resistance of the boat going through the water). Now like the other poster said, a current doesn't effect the boat speed through the water (SOW), just the speed over ground (SOG).Hey teach...can I go off now? Can I? Can I? Please, pretty please? awww...shucks.BTW: I used to be a diesel mechanic in my younger days so I think I know what I'm talking about.

 

[Kailani]

Fuel consumption

Let’s see...If I'm motor-sailing at 2100 rpm, my main is reefed at #1, my 130% is out, the boat is reaching, the wind is N/NW at 12 knots, boat is bucking a 3.2 knot ebb, I'm dragging a dingy with 2 bottles missing from a 12 pack, rudder’s at 3 degrees, factor the extra weight of the bird droppings on the forward hatch offset by the sun screen used over the weekend, calculate the friction created by the 30 weight oil (at operating temperature) splashing around in the Yanmar.... assume there’s less than 6 barnacles (evenly distributed) on the bronze 2-blade... anyone know the gravitational pull exerted during a waxing crescent moon on fiberglass vessels in the 38 degree latitude range?Whew, just thankful my fuel tank is a translucent plastic.

 

[Franklin]

Most important

"I'm dragging a dingy with 2 bottles missing from a 12 pack"Why did you leave the beer in the dinghy?

 

[tom]

What Happened to the Two Beers???

I agree 100% that things can be carried to extremes. I did almost run out of fuel motoring into a 20+ knot headwind across the bottom of Mobile bay and up the ICW towards Pensacola. I was used to my normal burn rate and hadn't checked the fuel all day and was really surprised when the fuel gauge read below empty...thank God for an inaccurate gauge. Fortunately we were not far from a marina. I expected the engine to die at any moment as we motored through rows of expensive boats with a strong crosswind. I sure could have used those two beers after we tied up.  But for all of my planning purposes I figure 0.5 gallon/hour and 10 miles/gallon. If I had been out in the bay I'd probably sucked air.

 

[Bob16841]

Average

What we need to know is the average fuel burn. Burns a bit more against a head wind, little less down wind, little more towing something, etc. I'm like Stu...I gas up based on hours of run time, not the guage.

 

[Bob16841]

Questions

After reading this thread again I have some questions. Ross said, "Generally diesel engines use about 9 ounces of fuel per hour per horsepower. That seems to hold true for all size engines." According to this formula, jviss should have burned 1.5 gph, not .44. (9 x 21 x 1= 189). I have a friend with a 300 hp diesel pick up. Using this formula, he'd burn 21 gph (9 x 300 x 1). Even at 10 mpg, he'd burn at most 7 gph. What am I missing here?In a small boat with a 21 hp engine using .5 gph, the wind, tide, sea conditions, etc are virtually irrelevant. He could be towing the QE II, and making no headway, what's the fuel going to be, maybe it doubles, now we are up to 1 gph. No boater in his/her right mind cuts it that close with fuel. Bert is right, as is Stu, who says we need a good average fuel rate for our boats to determine consumption.

 

[Moody Buccaneer]

it is per HP produced

9 oz per HP per Hour is for the HP in use. The 300HP truck is not running at 300HP for very long. if it takes 50hp to run the truck @ 50mph, then you get 50 x 9 or 450 oz of fuel to run 50 miles. 450 oz ~ 3.5 Gal, so about 14.3 miles per gallon.

 

[Tom Mendy]

Excellent

I've been pondering Kailani's response and my second Captain Morgan and Coke cleared things up perfectly!Thanks Kailani!

 

[filthy liberal scum]

fuel consumption is based on engine load

you need to go to your fuel consumption curve vs loading. be conservative and base it on that. you don't want to run it dry and have to bleed everything to get it going again. s/v QuePasa?

 

[R. Bounds]

Just curious?

I was just wondering with all this talk of exact fuel consumption, am I the only person that keeps a spare plastic can of diesel stored in the back? It takes up very little space stashed back in the lazerette and I rotate it to the tank every time I fill up. I fill up with a can anyway since I quit using that high sulpher red dyed water laden crap they sell at the dock. The motor runs a lot cleaner on auto brand and I the cost difference is offset by not having to change filters every time I turn around.

 

[chuckwayne]

spare can-yes!

you're not alone! we carry a spare jerry can and enough fuel line to use it as a direct supply if the main tank has issues. I also usually fuel from a land source, since it's a lot more convenient and the fuel's cleaner

 

[Bob16841]

"Your Honor...

...I rest my case."