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  1. #1
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    Fuel economy improvements on a 2.5L V6 BM150?

    Hello, I have a 1982 Mercury BM 150hp sn# 6101202

    I was wondering if there are any safe means for reducing fuel consumption on this era of motor?

    Yeah, i dont run full throttle, so that should help some, but was wondering if people have reduced the main jet size a bit or know of any tweaks to help out here.

    I tried searching "economy", this came up blank & when i searched "mpg", the msg board said too common or not enough letters.

    I cant afford a new fuel injected motor, so thats not an option for me at this time.

    Thanks, aby

  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Don't mess with jet sizes. Fuel is the lifeblood of that engine... not only does it keep combustion temps where they should be, it also delivers the OIL that lubricates the engine.

    Best thing you can do is run in the 3000-4000 RPM range (assuming you can get on plane and stay there within this RPM range).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  3. Member
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    #3
    Fuel economy can also be improved by correct engine height and a well matched Propeller, you could pick up a half a mile per gallon.
    Obviously that's assuming the motor is too low at the moment.

    Some good reeds also help.

    And as Don said, stay between 3000 and 4000 RPM, they tend to drink fuel above that.

  4. Member
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    #4
    Also, in case you decide to “upgrade” to an EFI, my understanding is that EFI motors from that era will not show a significant increase in mileage. You would probably have to switch to an Optimax for 2 strokes (or other high efficiency 2S) or move to four stroke. But all that will probably cost more than some extra gas. What boat is the motor on?
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay

  5. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #5
    Correct.... EFI provided relatively trouble-free, turn-key starting and permitted compensation for altitude and atmospheric changes.

    Overall- virtually identical fuel economy (as compared to carb models).


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
    Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor

  6. Member
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    #6
    This 150hp BM is on a 1982 ranger 350v.

    I dont have pics of the prop & the boat is away from me.

    I will get prop details in ~3 weeks time.

    Yeah, i've had my eye on reeds & reed spacers as well, but other items are requiring priority over the mpg at this time.

    Thanks for the brain storming, aby

  7. Member
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    #7
    Quote Originally Posted by leonreno View Post
    Also, in case you decide to “upgrade” to an EFI, my understanding is that EFI motors from that era will not show a significant increase in mileage. You would probably have to switch to an Optimax for 2 strokes (or other high efficiency 2S) or move to four stroke. But all that will probably cost more than some extra gas. What boat is the motor on?
    ^^^^^^+1
    .................................................. ...the scariest thing in life is the unknown ...................................

  8. Member
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    #8
    Here is a pic of my prop list the details.

    quicksilver 48 11070 A40 21P

    Besides the pitch, how much does that WHAMMY effect the performance of the prop?
    prop_1a.JPG

  9. Member
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    #9
    significantly it is disturbing water Infront of the other blades causing them to engage an aerated supply of water
    .................................................. ...the scariest thing in life is the unknown ...................................

  10. Member
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    #10
    Thanks for the insight Joe54

    The boat feels strong, but i havent really given her the berries, since it hasnt run in many years.

    Also, the tach isnt working on this boat, so i dont know the rev's.

    should i simply buy a direct quick silver replacement, get this tuned up or consider buying a similar pitched prop by another brand?

    I have zero experience fiddling with prop variables on any boat.

    With recent storms & such, it wont be for a while before i have the new electronics with gps to note top speed with the current set-up "as is"

  11. Member
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    #11
    First thing you need to do is get the tach working, can’t really judge the prop without a functioning tach. Does the tach not read at all? needle bounces around? The tach signal comes from the grey wire off the regulators, if you motor has two regulators you can switch the wires to see if that works, also, you can try and turn the selector dial on the back of the gauge, it’s a spin dial for
    different types of motors, note what it is on first then spin back and forth a few times with a small screwdriver and then put it back to the original spot, and test. This lightly cleans the internal contacts and can help a bad tach. Otherwise you need a new tach.
    Mercury 2002 200hp Carbed Saltwater
    OT566776
    2002 Cape Horn 22' Bay