Page 1 of 2 1 2 LastLast
Results 1 to 10 of 11
  1. #1
    SCHNORR12's Avatar
    Join Date
    Mar 2012
    Location
    Lake George, NY
    Posts
    834
    +1
    92

    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.

    RLACEMAN said:

    Quote Originally Posted by RLACEMAN View Post
    Its better, but you should be getting that kind of mileage or better if you were running full throttle all the time. Are you getting full rpms, should be 7K + 2 or 3 bars on the tach & speed? stock speedo should be in the 61-64. You said you had new plugs put in, take one out to check the color, should be a light brown, if dark there could be blockage in the air intake system or the ECU could be putting too much fuel in the motor. Are you getting your fuel at the same place, is it good quality? maybe try a different gas station. Most of us on this site have 15F's that are modified, they are about 5 or 6 mph faster than stock, which translates into .5 mpg better at most speeds because of hull & pump improvements. The worst mileage I ever got was 6.4 & that was a 60 mile river run at mostly full throttle.
    I am getting full RPMs. At WOT the speedometer usually reads 59-62. I had new plugs and oil at the beginning of the season and below will provide a picture of what the plug in cylinder 1 looks like right now. It does not seem to be showing anything significant. Should I remove the rest of the spark plugs as well and inspect them? I never get my fuel from the same place and my ski is bone stock.



    Any help would be appreciated. I feel like I am spending about double the amount of money on gas as I should be.


  2. #2
    Formerly Ultra250 TN Aquaholic6801's Avatar
    Join Date
    Feb 2007
    Location
    Old Hickory,Tn
    Posts
    5,446
    +1
    650
    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?

  3. #3
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
    Join Date
    May 2008
    Location
    Houston
    Posts
    4,485
    +1
    320
    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?


    Sean

  4. #4
    SCHNORR12's Avatar
    Join Date
    Mar 2012
    Location
    Lake George, NY
    Posts
    834
    +1
    92
    Quote Originally Posted by Aquaholic6801 View Post
    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?
    It's a 2008 with 52 hours. The ride plate and intake grate are on tight.

    Quote Originally Posted by smokeysevin View Post
    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?


    Sean
    I'm keeping track of distance from the ECU. I am turning 7,000ish RPMs at full throttle as it should be.

  5. #5
    RLACEMAN's Avatar
    Join Date
    Aug 2011
    Location
    Random Lake WI
    Posts
    884
    +1
    54
    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.

  6. #6
    SCHNORR12's Avatar
    Join Date
    Mar 2012
    Location
    Lake George, NY
    Posts
    834
    +1
    92
    Quote Originally Posted by RLACEMAN View Post
    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.
    Thank you for all your help so far. I found 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.

  7. #7
    SCHNORR12's Avatar
    Join Date
    Mar 2012
    Location
    Lake George, NY
    Posts
    834
    +1
    92
    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.

    Quote Originally Posted by smokeysevin View Post
    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?
    I am getting less than 5.3 MPG (WOT mileage) while never reaching speeds in excess of 40 MPH. Something is not right, but I can't quite figure out what it is.

  8. #8
    nicjak's Avatar
    Join Date
    Mar 2008
    Location
    Warragul, Downunder
    Posts
    7,794
    +1
    625
    maybe you are just stressing too much and worrying about nothing. if the ski is running good rpms im guessing you have no problem.

  9. #9
    Banned User
    Join Date
    Jan 2009
    Location
    LA/oc
    Posts
    3,911
    +1
    129
    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.

  10. #10

    Join Date
    Aug 2009
    Location
    Shuswap lake, Canada
    Posts
    170
    +1
    3
    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

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Fuel usage Ultra vs Lx
    By Fulldrawmike in forum Kawasaki PWC Performance (4-stroke)
    Replies: 6
    Last Post: 05-30-2010, 11:22 AM
  2. '96 780 SL vs. '94 750 SL SLT Fuel usage
    By WaveChaser in forum Polaris Open Discussion
    Replies: 16
    Last Post: 09-29-2009, 08:01 PM
  3. FZR Fuel Usage
    By Carlos Thomas in forum Yamaha PWC Performance (4-stroke)
    Replies: 4
    Last Post: 03-20-2009, 09:10 AM
  4. Fuel usage 250X
    By 308walky in forum Kawasaki PWC Performance (4-stroke)
    Replies: 10
    Last Post: 01-27-2009, 02:42 AM
  5. Speedster 150 Fuel Usage
    By jasonb225 in forum Sea Doo Sport Boats
    Replies: 4
    Last Post: 05-14-2007, 06:25 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •