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Volvo Penta AQ225 eating fuel!!

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  • Volvo Penta AQ225 eating fuel!!

    Hey guys i have a fairly new to me 24’ cabin cruiser boat with the volvo penta 225 5.0L V8 with volvo penta 280 outdrive single prop.

    My problem is i took it to prince rupert west coast of BC and i ran out of fuel on my way back pretty close to the marina... i know my fuel tank is small 57 gallons but i only did 100kms of distance and kept the boat planing at 3400RPM trim tabs up.
    spent some of this day on the kicker salmon fishing 15hp honda 4 stroke, at 3500rpm im doing 42-43km/h.
    is there something wrong with my carb or is this semi normal?

  • #2
    100 kms is 62.5 miles with a 57 gallon gas tank you're getting approx. 1 mile per gallon. I'd think you could do better than that, when was the last time it had a tune up? Spark plugs, carb cleaning and adjustment, etc. Simple thing: after starting the engine remove the flame arrestor, does the auto choke open all the way after the engine reaches normal operating temp? If not that engine will be running on a very rich fuel mixture which could explain this problem, as well as fouled spark plugs with gaps that are too large, corroded distributor cap etc. These engines are very simple but its auto tech 101 from 50 years ago....not everyone gets that...except us older guys who grew up with cars...that were exactly the same....
    1988 Four Winns 200 Horizon
    4.3 OMC Cobra

    98 Jeep Grand Cherokee 4.0 Selectrac
    07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

    "While air doesn't freeze....rust never sleeps"

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    • #3
      A good idea is to clean the spark arrestor as well. It could be crusty. I helped a friend with a similar issue on a 5.0L GM Merc that had such a clogged spark arrestor the engine was in sort of a permanent choke situation. Easy clean out with brake cleaner and going again with much better results. The spark arrestor should not need very much cleaning but its something that could be overlooked for a very long time.

      Beyond that I'd say look into ignition issues, distributor cap/rotor corrosion, plug wires that have wear marks in the OD of them or crusty fouled plugs will do it too. Its also a possibility that the coil itself is breaking down. I've replaced 2 of those on GM trucks which were probably 20-25 years old but eventually the windings became compromised. One failed instantly and the other was leaking "spark" out the side of it to ground.

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      • #4
        pull the plugs and read them. are they black, or a nice brown color?

        however your 24' cruiser is a bit on the heavy side for a 5.0 liter, so your 3400 RPM / 42kph (26mph) cruise may be taking about 170-180hp

        assuming 180hp and a BSFC of.4#/HP/hr, you should be burning 72# of fuel or 10.6 gallons per hour (steady state). at a trip of your 100kms, you should have burned thru about 30 gallons.

        assuming your 15hp kicker was running at about 10hp for 4 hours, you would have burned about 3-4 ballons there

        your burning a bit more.

        things to look at.
        • weigh your boat. if your boat is heavier than its supposed to be, you burn more fuel
        • look at your hull, is the hull clean of growth
        • look at your timing
        • look at your prop. are you able to get to 4500 RPM at WOT? if not, you may be over-propped which leads to lugging which also burns more fuel.
        • look at your compression. if your numbers are lower than 120psi in each cylinder, the motor would be putting out less power per amount of fuel, so you would need to have more throttle (burn more fuel) to move the load
        • look at your carb - you should have the holley on the 225. if you had a backfire, you may have ruptured the power valve. if that is the case, you would be burning more fuel than normal off idle, as it will run rich

        Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

        Past Boats
        1970 Wooster Hellion - Merc 9.8
        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

        What’s behind you doesn’t matter.Enzo Ferrari

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        • #5
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          I’m guessing that there is no way you used that amount of fuel without the engine throwing it out the exhaust or into the sump. Even then. Your bilge would be full of fuel and your engine wouldn’t run right.
          Are you sure you used that ? Did you put that in and it ran out ? Or are you just going by the gauge ?
          Is there a blockage maybe ?

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