Thread: Excessive Fuel Usage - STX15
06-25-2012, 01:17 PM #1
Excessive Fuel Usage - STX15
I have determined that my 2008 STX15F is using more fuel than normal. Here is a link to the thread where the discussion originated after I had a question about the fuel gauge on the ski. According to a thread on PWCToday.com, this ski should be getting 6 MPG at WOT. I have not yet run an entire day at WOT but I am still getting lower gas mileage than what the ski should run at WOT. Here are my numbers (my tank is always filled to the same spot):
6/21/12 - 38.8 miles. 8.908 gallons of fuel consumed. = 4.35 MPG. This day consisted of 40% cruising at 35 MPH, 20% WOT, and 40% idling and messing around doing circles and hitting the occasional wake.
6/23/12 - 45.5 miles. 8.938 gallons of fuel consumed. = 5.09 MPG. This day consisted of 10% buoy course, 20% WOT, 50% cruising at 35-40 MPH and 20% wave jumping.
Any help would be appreciated. I feel like I am spending about double the amount of money on gas as I should be.
06-25-2012, 01:34 PM #2
Plug looks about normal......I had a 2006 15f....thats about right on for fuel consumption it could be a lil bit better...... 5 to 6 mpg is about right, depending on your throttle control....if you are riding with faster skis you will be riding harder to keep up....I know thats where I lost the fuel economy of the 15f.......
What year and how many hours?
Anything loose like the ride plate or intake grate?
Any excessive prop clearance?
06-25-2012, 01:39 PM #3
Don't worry about it, if the plugs foul (which they don't look too bad) check the fuel pressure, otherwise just enjoy it. The fuel tank is 16.4 Gallons and straight from the manual the specs are cruising range of 87 miles at WOT 1 hr and 37 minutes which works out to 5.3 mpg. Riding conditions and a whole ton of other factors come into play. How are you keeping track of distance and how many rpms are you turning at full throttle?
06-25-2012, 01:41 PM #4
06-25-2012, 01:55 PM #5
That spark plug looks perfect, if speedo says 62 that is about right for a stock boat, but you cannot always go by the speedo, they usually read high, but occasionally can be very close, mine reads 70 by the time I have high 63 on the GPS, but the odometer part of it is very accurate. You could have a worn or damaged impeller & it doesn't take much damage to make a huge difference. You should at least be able to get 5.5 on a stock ski, but that would be constant full throttle.
06-25-2012, 02:04 PM #6
this which indicates that I should be getting 8 MPG at 40 MPH. Maybe next time I go out I should try and keep the ski at 40 MPH and see what kind of MPG I get as a result. How do I get to the impeller? How would I tell if it was damaged? When I bought the ski a friend of mine who works at the local dealership took the jet pump apart to make sure that was fine and he said it was in great shape.
06-28-2012, 05:46 PM #7
Unfortunately today's riding further confirmed that I have some sort of issue with my ski. In order to get a more accurate figure I decided to put my ski in SLO mode for the day limiting myself to 40 MPH and 5,000 RPMs. 90% of the riding was between 25-35 MPH with 5% being at idle speeds and the other 5% at 39-40 MPH. In total I rode 44.5 miles. After pulling the ski from the lake, it took 8.958 gallons of fuel in order to reach the same level it was at before riding. This comes out to roughly 4.97 MPG.
According to what Sean said here, the manual claims you should be getting about 5.3 MPG at WOT.
06-28-2012, 05:50 PM #8
maybe you are just stressing too much and worrying about nothing. if the ski is running good rpms im guessing you have no problem.
06-28-2012, 06:13 PM #9
- Join Date
- Jan 2009
Screwing around will get nett you less mpg as well as the slow key. Your skis fine also anything printed is a estimate what people pos are not always accurate as well just enjoy your ski.
06-28-2012, 08:10 PM #10
- Join Date
- Aug 2009
- Shuswap lake, Canada
Think this is a highly questionable way to judge fuel usage. I prefer to calculate gallons used per hour and even at that I see quite the variation. My 12f and 15f seem to use similar amounts of fuel if they are on the same mission.
Is the ski running smoothly? Holeshots are strong? Top end is where it should be?
I find that others often under-report fuel usage....as if there was some kind of competition. This happens with aircraft, cars, bikes, jetskis and I have no idea why anyone would bother!
Boats take lots of power and that is just how it is
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