Fuel economy of a 175 skiing

[c9908928]

How much fuel would i expect to use in, say 5 hours skiing with a 175Hp johno 1999 model

 

[ob]

Re: Fuel economy of a 175 skiing

A 2 stroke outboard consumes roughly 10% of its rated horsepower per hour at WOT.A 175 would fall at around 17.5 gallons per hour by this method.Since you will not be running the engine the entire 5 hrs at WOT while pulling skiers I would estimate that you will use considerably less fuel depending on the time actually spent operating motor.As a guess ,I would say that you will need between 40 and 50 gallons of fuel to begin your 5 hr. skiing day.

 

[Trevor]

Re: Fuel economy of a 175 skiing

thats an expensive day!!!!!!!

 

[c9908928]

Re: Fuel economy of a 175 skiing

Surely its not that much fuel

 

[JHOLE]

Re: Fuel economy of a 175 skiing

Maybe that's uphill. <br /><br />I have an older 175 rude on a 21' cc, 45mph at WOT. If I went for a 5 hour trip - 225 miles - then ob's numbers make sense. There are obviously a lot of factors - prop, boat, load, water condition, etc. input would help but I'm going to guess 20 gal + - .

 

[jasonnb]

Re: Fuel economy of a 175 skiing

Just for comparison sake, with my 85hp Johnson crossflow V4, that would take about 15 gallons. I would guess 25 or more for your 175.

 

[rons boat]

Re: Fuel economy of a 175 skiing

To make this discussion interesting I am throwing out a couple of complications since the 10% formula you use sounds reasonable. But you used the motor HP without regard to load for calculations. I would think you need to know what drag is being overcome to calculate. If your boat has little drag, then the amount of hp actually used is small and if your boat is a barge and has lots of drag then you need to know that. I think using the motor rated horsepower is only a small factor in calualtions but I do agee that an idling 175 uses more that a 100 idling. For my final complication: These new injected blown engines have become more efficent, I suspect some of us old timers are going to have to revise our formulas. Good discussion. Ron

 

[Hooty]

Re: Fuel economy of a 175 skiing

Hummmm.<br />Since one piston moves down and pulls in x amount of fuel and air, the only difference in the amount of fuel and air it pumps in is number of times it does it in a given period.<br /><br />c/6<br /><br />Hooty

 

[heatstroke]

Re: Fuel economy of a 175 skiing

a bunch of us used to slalom ski for 6 hrs on weekends and burned about 200 litres or about 45 gal on a 200hp yamaha.

 

[heatstroke]

Re: Fuel economy of a 175 skiing

a bunch of us used to slalom ski for 6 hrs on weekends and burned about 200 litres or about 45 gal on a 200hp yamaha.

 

[rons boat]

Re: Fuel economy of a 175 skiing

Hooty makes an interesting point, However he does not point out that constant piston speed can occur at all throttle settings depending on load. Throttle settings determine fuel flow and consumption not speed of piston. My airplane can glide with constant speed and almost no fuel flow (for a while) Ha ha. My point, tell us about your boat size and hull and passengers in the tow boat as well as number of skiers and weight. This is supposed to be fun and I am getting ridiculeous. Ron

 

[ob]

Re: Fuel economy of a 175 skiing

There are obvious reasons why the exact amount of fuel consumed can't be calculated with the info provided which is why I recommend he "begin" his 5hr. day with 40 to 50 gallons if he doesn't like to live dangerous.Big 2 stroke motors require big fuel tanks for extended run time and if the total 5 hrs is spent pulling skiers .................

 

[Autotech]

Re: Fuel economy of a 175 skiing

For comparison I have a 65 hp that pulls water toys all day on 12 gal. gas usually for the younger lighter kids. As they got older 65 wasnt fast enough for the salom and barefooters so we went to inboard 140 that runs all day on 25 to 30 gal. The difference is the boys wanted to go faster on salom heance more fuel. Something to look forward to though, is when they get old enough to bring there own gas. Saved me 100.00 bucks a weekend at least. down side I still had to feed them. So I really didn't save anything especially when they bring there friends. On the up side I enjoyed knowing they were on the lake having good clean fun which made it worth 3 times more than it cost. Ski on at any cost.<br />Bobby

 

[rons boat]

Re: Fuel economy of a 175 skiing

Autotech: I think you have it all figured out.