How to match propeller with engine?

Discussion in 'Diesel Engines' started by ZeusGaryulo, May 18, 2016.

  1. ZeusGaryulo
    Joined: Mar 2016
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Southampton

    ZeusGaryulo New Member


    I am helping in the design of a 60' powerboat, is going to have two MAN V8-1200 engines (882 kW-2300 rpm), my question is, should I calculate the propeller to point A (882 kW-2300 rpm), point B (95% rated power-2300 rpm) or point C (95% rated power-95% rated rpm) of the engine curve?

    I have read that is not a good design choice to design for point A, because there is not power allowance if the engine needs to provide some extra power.

    I also have read that diesel engines works really confortable at maximun rpm and almost maximun power (95% let's say), but my doubt is that when the engine gives its rated power it would rotating at higher rpm than rated (103% let's say). That's why I cannot decide between point B and C.

    Someone can help me?

    Many thanks!
    Joined: Oct 2002
    Posts: 4,519
    Likes: 111, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    For longest service life and lowest fuel burn per HP many large engine folks will suggest 80% of rated power at 90% of rated RPM.

    Low fuel burn and long engine life should be more of a concern than the last K of speed.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.