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ContinuousWave: Whaler Performance
Johnson 225 Ocean Runner Fuel /OIL Consumption
|Author||Topic: Johnson 225 Ocean Runner Fuel /OIL Consumption|
posted 03-22-2004 01:26 AM ET (US)
I have a 1996 Johnson 225 Ocean Runner on my 1996 BW 22' "Justice". Does anyone have an idea as to what I should be seeing in fuel and oil consumption per hour of operation at 4000/5000 rpm?
posted 03-22-2004 08:49 AM ET (US)
A pretty good estimate for a carbed 2-stroke would be 10% of total horsepower at wide open. 225hp x .10 = 22.5 gal/hr.
About half of that at a "comforable cruise". (3500-4500 rpm)
225hp x .05 = approx. 11-12 gal/hr.
Of course these are estimates. Assuming you have the right prop for your purposes. If you load the boat with 7 people and gear, full tank etc, you'll use a lot more.
Over the years, with carbed 2-strokes, these estimates have been pretty darn close. These include 13'SS, 17'Nauset, 20'Revenge, 25'Revenge. Only Whalers.....of course!
posted 03-22-2004 08:58 AM ET (US)
Oh yeah...I forgot oil.
I just figure on 50:1 and be done with it.
Yes, less at lower speeds, maybe 150:1 at troll/idle etc. etc. For every 50 gallons of gas...one gal of TCW-3
But I estimate 50:1 for everything, then I know I've got enough in the oil tank.
I always carry an extra gallon of Yarmalube, no matter what.
I've "donated" more than a couple of gallons in my day for those guys that ran out.
posted 03-22-2004 01:33 PM ET (US)
Thanks for the insight. How about the use of 87 octane gas? I've had a recent opinion suggesting that I should only run mid-grade (89) fuel in the 225 Johnson...what do you think? Cost is important.
posted 03-22-2004 01:59 PM ET (US)
A good estimate of fuel consumption by an internal combustion engine is that it will consume 0.5 pounds per hour per horsepower. This works for many types of engines. Modern engines may be more efficient than this. Let's see if that jives with the estimate given above.
At 225-HP, you will burn 113 pounds of gasoline in an hour. That is about 20 gallons per hour. This is fairly close to the estimate given about as 22.5 gallons per hour.
There will be quite a difference between 4000 RPM and 5000 RPM.
It is hard to say how much horsepower you are using at a certain RPM.
posted 03-22-2004 02:16 PM ET (US)
Thanks much...what are you using as the weight of 87/89 octane fuel (113 lbs divided by 7 lbs per gal of weight would be about 16 GPH)but at what RPM?
posted 03-22-2004 10:02 PM ET (US)
My 225 Evinrude Ocean Pro would burn upwards of 28 gph at WOT (floscan) and would cruise at 4200 rpm with 14gph burn. In my 21 Outrage this equated to 24 knots.
posted 03-22-2004 10:04 PM ET (US)
BTW, my Evinrude was a 1996 model too, so this emperical data may help you.
posted 03-22-2004 10:32 PM ET (US)
The density of gasoline is given as 0.67 gram/cubic-centimeter
Thus gasoline weighs:
0.67 grams 1000 ml 3.7854 litre 1 kg 1 lb. 6.8 lbs.
posted 03-22-2004 10:57 PM ET (US)
Yes, my math was off in my earlier example. :-(
Weight of Gasoline
It must vary depending on the temperature and the grade of gasoline.
Let's call it 6 lbs./gallon.
Fuel Consumption Per Hour Per Horsepower
Here are some figures from:
---begin quoted material----
Typical BSFC ranges are as follows. As usual, there will be exceptions, but this should serve as a general guide:
0.26-0.34 Large industrial four-stroke diesel engines (very small hp/weight ratios)
0.28-0.36 Other four-stroke diesel engines
0.32-0.38 Two-stroke diesel engines
0.37-0.44 Fuel injected four-stroke gasoline aircraft engines
0.40-0.48 Fuel injected four-stroke gasoline automobile engines
0.43-0.48 Carburetted four-stroke gasoline aircraft engines
0.48-0.60 Carburetted four-stroke automobile engines
0.55+ Two stroke gasoline engines
0.55-0.70 Four-stroke aircraft engine takeoff fuel flows
Engines don't maintain a fixed BSFC over their entire range. Typically an engine's BSFCs when producing only a fraction of its rated power are quite high. This is due to thermodynamic factors which limit the engine's efficiency when it runs cold. BSFCs typically reach their lowest value for the engine in the 50-80% power range. Then then begin to trend upward again as friction begins to play a dominant role and/or the mixture must be enriched to provide for adequate engine cooling.
------end quoted material----
With these new numbers, let us re-calculate the fuel consumption of a 225-HP 2-stroke gasoline engine in pounds per hour:
225 X 0.55 = 123.75 pounds
If we are using 6-pound/gallon gasoline that will be
20.625 gallons per hour.
Note that the reference above suggests that the lowest value is obtained in the 50-80% range of the engine power. This may explain why "cruise" is the most efficient speed. At WOT the engine would probably burn more fuel per hour than calculated using the 0.55 figure
At 50% throttle we would only be making 113 HP thus burning about
113 X 0.55 = 62.15 pounds or 10.4 gallons per hour
posted 03-24-2004 01:09 PM ET (US)
Ya know many people have been "cited" for posting an answer that they have no real hands on experience with, is this thread excluded? Not to be a buster but 3 pages of math equations is probably not what he was looking for.
I OWN a 225 Ocean Runner and I do burn 23.5gph at WOT. She will consume 11-14gph at cruise(35-4200) and will consume a gallon of oil to every tank of fuel I burn(85gal capacity) which is usually about 8-10 hours per tank. I run 89 or 93 octane and do not run 87 in anything I own. If cost to run it is a deciding factor....you own the worst engine being its appetite for fuel. For $.10/gal, run 89 if possible, not gonna kill ya being it is only another $5-8 per fill-up. Run good quality oil as well, not the Sears brand.
I fill mine usually with 5gal jugs and one day my friend said it is sad that it takes longer to fill the tank than it does to burn it.
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