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  • 12th July 2023 at 16:10 #9078
    Charles TilleyCharles Tilley
    Participant

    I have a Volvo Perkins MD30A 1986 engine on my Macwester Seaforth 36.  I have asked many people but have so far not been able to get an answer as to the optimum RPM for speed and fuel economy.  I would welcome views.
    Thanks   Charles

    Thanks.  Charles Tilley

    12th July 2023 at 19:01 #9080
    Mike HotardMike Hotard
    Participant

    Hi Charles, my Seaforth has a BMC so can’t advise on a Volvo. However on a calm day with a reasonably calm sea I just motored in my Seaforth keeping an eye on the engine revs and boat speed. There comes a point when extra revs don’t actually make the boat go faster. To me that is the optimum point and I just knock the engine back a couple hundred RPMs now when using the motor.

    15th July 2023 at 17:47 #9083
    Charles TilleyCharles Tilley
    Participant

    Thanks Mike.  With your BMC engine and a flat sea what is your optimal speed?

    Best wishes

    Charles

    15th July 2023 at 20:14 #9084
    Mike HotardMike Hotard
    Participant

    Hi Charles,

    Seabird will do around 6 knots with a clean hull motoring.
    Best regards

    Mike

    15th July 2023 at 22:34 #9085
    Charles TilleyCharles Tilley
    Participant

    Thanks Mike.  Very helpful.  Brizo does 5 knots but I think I am being very conservative on RPM at 1700.

    Best wishes

    Charlex

    20th April 2024 at 14:53 #9363
    Peter LloydPeter Lloyd
    Keymaster

    I have a White II which has an Optimal speed of about 4.5kt at 1800 revs. At that speed I average about 1.9lts/hr.  If I pick the speed up to 6kt at 2200 revs the fuel consumption goes up to about 2.5lts/hr.

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