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Garmin Fuel Flow Sensor

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    For the 285 I once had and now our 305 running at 1800 to 2000 rpm generally put us plowing water at a high fuel burn rate.

    I find better economy coming down to a fast idle without making a big wake or get it up on plane.

    On plane our 285 with 5.7 fuel injected got 1.6 MPG.
    On plane our 305 with twin carb 5.7s get 1.1 MPG.
    The 305 at fast idle gets about 2.4 MPG.
    Jim McNeely
    New Hope a 2004 Bayliner 305 Sunbridge Express Cruiser
    Twin 5.7s with Bravo2 drives
    Brighton, Michigan USA
    MMSI # 367393410


      Originally posted by Nickp View Post

      Sorry it took so long to respnd...

      GPS/Speed Over Ground (SOG) does not take current into account...for example, if you were heading upriver with 2 knots of current in your favor your SOG would read 2 knots faster...likewise if you were in fowl current you would see a SOG of 2 knots slower than actual (over water). When viewing Speed Over Water (SOW), you will see the actual speed of the boat going through the water. GPS Nautical Miles does not care about speed so true nautical miles would be captured. On the other hand, a trip odometer based on SOW would not measure accurately because it does not care about actual miles traveled.

      Extreme example...if your boat were traveling at 15 knots over water and you were facing a fowl current of 15 knots, the boat would stand still compared to the surroundings. Your GPS Nautical Miles would register 0 NM after an hour but your water speed instrument/odometer would register 15NM...

      Does this help...?
      That helps - thanks!
      97 2859


        My, I did not expect this thread I started to extend this far! With only two seasons experience with our 2959 (which we love), and only a half season with a fuel flow monitor, it's pretty clear to me that speeds above "hull speed" and less than planing speed is not the way to go. I have my instrument set to display GPH. Water speed (Kn) less than GPH = BAD (inefficient0. Water speed (kn) greater than GPH = GOOD (efficient). Seems like the 2859's "sweet spot" is about 17 to 18 knots (3600 TO 3700 PPM). At that speed the fuel flow monitor is showing about 16 GPH, which seems to be about as fuel efficient as your going to get). My boating buddy would point out that neither the water speed, nor fuel flow ihas been calibrated, which is important to note.