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Old 11-06-2013, 05:07 AM
Mark rsa2au's Avatar
Mark rsa2au Mark rsa2au is offline
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Fuel Consumption is this reasonable?

Hi Guys,

Need you collective opinion on fuel consumption and how you accomodate the small fuel tank?

After spending many hours working to get the boat ready for summer we finally spent a few days at the lake. We did 9 hours and used 280lt or 74 gallons or about 8.2 gallons per hour (31lt per hour). (PS spend 31 hours on the hour meter just in servicing and testing)

Does this seem reasonable, it seems high to me? This was mostly sking, the kids on wakeboards and inflatable tubes, and a few barefoot runs. I dont use full throttle, and dont burn arround as it stuffs the water. Just easy up, ski, and coast down in a straight line - idle back to skier.

I also find the tank is just not big enough for a full days sking and I need to top up with 5 gallons or so to finish the day. What do you do to keep from running out of fuel?

this is me burning fuel on my second run of the season.....
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  #2  
Old 11-06-2013, 05:48 AM
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Grant777 Grant777 is offline
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My X-2 with the MCX engine burns 18liters per hour. Weighted with wakeboard ballast and surfing. 31liters per hour sounds excessive.
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Old 11-06-2013, 05:52 AM
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g-mantrix g-mantrix is offline
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Fuel Consumption is this reasonable?

Seems fairly thirsty, what boat and what engine?
For example, my 07 X2 with 350MCX run full ballast plus additional bags total 1100kgs 8 peeps and wakeboarding of course, 2o-22 ltrs per hour
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Old 11-06-2013, 06:23 AM
Coolerking Coolerking is offline
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Boat: Mastercraft x-star, 2008, LY6
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Fuel consumption

Yep doesn't sound right 31 litres.
I have a 2008 X-Star with an Indmar 4 litre in it, zero additional ballest, six people (four adults), doing from 18-22 mph, I burn around 20 litres and hour. Assume you are doing 30ish for skiing? Would the increased speed make that much difference?
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Old 11-06-2013, 07:09 AM
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bturner2 bturner2 is offline
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Boat: Maristar 200VRS w/ X2 Package, 2007, 310HP
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Slalom skiing, bare footing and especially tubing will burn through the gas. We had a 4 person tube that put such a drag on the boat that you could watch the gas gauge move while you were pulling. It was like running the boat with a sea anchor attached to the back. Kids loved it but it worn out this summer and will be replaced with a smaller one for next year.

A lot will also depend on what prop, ballast/load and altitude your using the boat in. Your numbers sound high but if you had a hour with our old tube in there you'd be right in line with what we were seeing.
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Old 11-06-2013, 07:54 AM
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Mark rsa2au Mark rsa2au is offline
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Boat: Mastercraft X5 2001. 310hp preditor
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Boat is a 2001 X5 with a 310hp TBI Preditor motor. No Balast and about 3 or 4 adults in the boat, skis and life vests.

Changed from previous 13 x 13 4 blade prop to 12 x 15pitch 3 blade for more top end but did not measure fuel consumption on the 4 blade prop. New prop seems to give a much flatter wake, better top end. Pull up is softer but still great for us.

I know it is difficult to judge fuel burn, as it does realy depend on the type of watersports, and the driving style. Also on hull design, prop, and condition of the motor etc...

I am comparing to my mates Malibu which although longer weighs about the same and his average over the week end was about 20lt per hour (mercruiser 350 motor I think).

Also comparing it to my previous Sea Ray where doing the same stuff at the same place we never ran out of fuel in a day from an 80 lt (21 gallon) tank. Now I am using 150 lt (40 gallons) doing the same stuff but in a different boat.

I am happy to accept a higher fuel burn for more power and a better wake... but at today's fuel prices having to pay nearly 70lt (20 gallons ) Extra per day will limit my sking severly.

I know it sounds strange but I will be happier to know there is something broken that I can fix, rather than accept that this is normal.

Cheers
Mark
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Old 11-06-2013, 08:10 AM
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bturner2 bturner2 is offline
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I don't think I've ever heard of anyone running a 12" prop on that boat. You may want to send a note to or call Eric at OJ and see if he would have a better solution for you. I'm leaning towards the prop as the culprit in this equation.
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Old 11-06-2013, 09:39 AM
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JimN JimN is offline
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Quote:
Originally Posted by Mark rsa2au View Post
Hi Guys,

Need you collective opinion on fuel consumption and how you accomodate the small fuel tank?

After spending many hours working to get the boat ready for summer we finally spent a few days at the lake. We did 9 hours and used 280lt or 74 gallons or about 8.2 gallons per hour (31lt per hour). (PS spend 31 hours on the hour meter just in servicing and testing)

Does this seem reasonable, it seems high to me? This was mostly sking, the kids on wakeboards and inflatable tubes, and a few barefoot runs. I dont use full throttle, and dont burn arround as it stuffs the water. Just easy up, ski, and coast down in a straight line - idle back to skier.

I also find the tank is just not big enough for a full days sking and I need to top up with 5 gallons or so to finish the day. What do you do to keep from running out of fuel?

this is me burning fuel on my second run of the season.....
Attachment 102842
What is the temperature rating for your thermostat? Use a 160 degree- it keeps the engine in its best operating range and that means it burns less than when using a 142 degree thermostat. If the air temperature is high, open the engine cover if it will sit for more than a couple of minutes after running it and let it idle for a minute after hard runs. Also, verify the resistance of the coolant temperature sensor-if it's more than about 200 Ohms after running it for more than a minute, it's too high and will cause the engine to run rich. If you quickly move the throttle from idle to high and it bogs, it would seem to reinforce suspicion of the bad ECT or low temperature ECT.

Do your gasoline smell strongly of gasoline? If so, check this.
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Old 11-06-2013, 09:58 AM
Mark rsa2au's Avatar
Mark rsa2au Mark rsa2au is offline
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Quote:
Originally Posted by JimN View Post
What is the temperature rating for your thermostat? Use a 160 degree- it keeps the engine in its best operating range and that means it burns less than when using a 142 degree thermostat. If the air temperature is high, open the engine cover if it will sit for more than a couple of minutes after running it and let it idle for a minute after hard runs. Also, verify the resistance of the coolant temperature sensor-if it's more than about 200 Ohms after running it for more than a minute, it's too high and will cause the engine to run rich. If you quickly move the throttle from idle to high and it bogs, it would seem to reinforce suspicion of the bad ECT or low temperature ECT.

Do your gasoline smell strongly of gasoline? If so, check this.
Thanks Jim.

Thermostat is a 160. IR heat gun and Temp guage on dash confirms. ECT has been replaced, and all other sensors have been checked or replaced. Motor does not bog down on full throttle pull off.

I can still smell strong fuel smell at the rear of the boat with puffs of diesel like black smoke on some hard pull outs, but it is way better than before when I had black sooty residue up the transom. New fuel filter and pump, new fuel lines, new pressure regulator. Currently set at 32 PSI (factory spec is 30psi) but this 2 PSI should not create such heavy consumption - if it is heavy as I do not know what is "Normal".

It would be nice if adjusting the 2PSI down would make that much difference but I doubt it. I wanted to find out what the "average" was before looking for an issue.

If the collective intellegence on this forum suggests it is high I will be adjusting the PSI down, and then retesting all sensors, and perhaps spending a day with the 4 blade 13 x 13 to compare.

Cheers
Mark
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  #10  
Old 11-06-2013, 12:26 PM
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JimN JimN is offline
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Quote:
Originally Posted by Mark rsa2au View Post
Thanks Jim.

Thermostat is a 160. IR heat gun and Temp guage on dash confirms. ECT has been replaced, and all other sensors have been checked or replaced. Motor does not bog down on full throttle pull off.

I can still smell strong fuel smell at the rear of the boat with puffs of diesel like black smoke on some hard pull outs, but it is way better than before when I had black sooty residue up the transom. New fuel filter and pump, new fuel lines, new pressure regulator. Currently set at 32 PSI (factory spec is 30psi) but this 2 PSI should not create such heavy consumption - if it is heavy as I do not know what is "Normal".

It would be nice if adjusting the 2PSI down would make that much difference but I doubt it. I wanted to find out what the "average" was before looking for an issue.

If the collective intellegence on this forum suggests it is high I will be adjusting the PSI down, and then retesting all sensors, and perhaps spending a day with the 4 blade 13 x 13 to compare.

Cheers
Mark
Check for codes- if code 33/34 comes up, it points to the MAP sensor and this could cause problems like you're describing. Also, if you want to check the fuel "cone" from the injectors, remove the flame arrestor, start the engine and shine a timing light on the cone. It's like stop-action, so the gas will look like it's not moving at all, if it even looks like it's moving. If you see any gaps (called 'tearing', as in 'tearing' paper), it could be that the injectors need cleaning, could be a faulty regulator or something along those lines. Also, the knock sensor's operation should be verified- run the engine and watch the timing advance as you increase RPM. I would recommend doing this while under way, not in idle, but it will advance in either case. When the timing has advanced, hit a motor mount with a hammer (on top of the large adjuster bolt at the deck is a good place) to watch for the timing to change. If it doesn't change, use a screwdriver and tap on the knock sensor and look for the timing to retard. You should have base timing at 10BTDC and should see about 30-35 of additional advance, for total advance of about 40. If you don't see this much advance, unplug the knock sensor wire and see if it helps. If it does, you may have a bad knock sensor.

If you didn't put it into diagnostic mode when you set the timing, you need to do that, or it's not correct. The timing mark will be stable when it's in this mode and when it's jumping around, it's not possible to be accurate. Watch the timing light on hard acceleration- if it skips, you may have mid-fire. If the plug wires haven't been changed (I don't remember all of what you wrote about changing) and they're more than a few years old, you could have cross-fire.
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