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Did Atkin mean BHP or SHP?

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  • adharvey2
    I m wondering if when Wm. Atkin wrote about those older small gas inboard engines like the Grays, Scripps, Universals, etc., should the HP ratings he quotes be
    Message 1 of 5 , Jul 19 6:42 PM
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      I'm wondering if when Wm. Atkin wrote about those older small gas
      inboard engines like the Grays, Scripps, Universals, etc., should the
      HP ratings he quotes be thought of as BHP or SHP? I'm thinking that
      since they were marketed as marine engines, often with gear included,
      that maybe the HP figures were meant to be taken as SHP, but I"m just
      quessing.
    • Ronald Fossum
      Having worked the SHP for various props that Atkin recommended for his boats and comparing those with the engines he mentions, my results indicate SHP -
      Message 2 of 5 , Jul 19 7:38 PM
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        Having worked the SHP for various props that Atkin recommended for his boats and comparing those with the engines he mentions, my results indicate SHP - usually.


        ----- Original Message -----
        From: adharvey2
        To: AtkinBoats@yahoogroups.com
        Sent: Thursday, July 19, 2007 6:42 PM
        Subject: [AtkinBoats] Did Atkin mean BHP or SHP?


        I'm wondering if when Wm. Atkin wrote about those older small gas
        inboard engines like the Grays, Scripps, Universals, etc., should the
        HP ratings he quotes be thought of as BHP or SHP? I'm thinking that
        since they were marketed as marine engines, often with gear included,
        that maybe the HP figures were meant to be taken as SHP, but I"m just
        quessing.





        [Non-text portions of this message have been removed]
      • John Kohnen
        The ratings of older engines were a bit conservative, more like contiuous or maybe medium duty for the high speed engines, rather than the peak
        Message 3 of 5 , Jul 23 8:56 PM
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          The ratings of older engines were a bit conservative, more like
          "contiuous" or maybe "medium duty" for the "high speed" engines, rather
          than the "peak" horsepower most modern engines are advertised at. An old
          engine rated at 2000 rpm is designed to run at 2000 rpm all the time. So
          my guess is that the ratings are BHP, but conservative. Most of the Atkin
          designs don't use a power robbing reduction gear either, though you'll
          usually need to use one with modern engines in the same designs.

          But. I've run across a curious thing in the listings of marine engines in
          old Rudder magazines I've been looking at, some manufacturers give the
          rpm. of their engines at the output shaft if there's a reduction gear.
          Thus an engine that is rated at 2000 rpm with a straight through reverse
          gear is rated at 1000 rpm. if it has a 2:1 reduction gear! That points to
          the possibility that hp. is rated at the output shaft too, except that the
          hp. figures are the same for the same model engine whether it ahs a
          reduction gear or not... <shrug>

          On Thu, 19 Jul 2007 18:42:27 -0700, adharvey2 wrote:

          > I'm wondering if when Wm. Atkin wrote about those older small gas
          > inboard engines like the Grays, Scripps, Universals, etc., should the
          > HP ratings he quotes be thought of as BHP or SHP? I'm thinking that
          > since they were marketed as marine engines, often with gear included,
          > that maybe the HP figures were meant to be taken as SHP, but I"m just
          > quessing.

          --
          John <jkohnen@...>
          People say that life is the thing, but I prefer reading. <Logan
          Pearsall Smith>
        • alankornhauser
          Gears are very efficient. According to Mark s Handbook, the efficiency of single reduction spur gears is 93-96%. Since most marine gearboxes are
          Message 4 of 5 , Jul 24 8:38 AM
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            Gears are very efficient. According to Mark's Handbook, the efficiency
            of single reduction spur gears is 93-96%. Since most marine gearboxes
            are single-reduction, this means that SHP is almost identical to BHP.

            If you think anything on a boat is designed to better than 7% accuracy,
            think again!
          • adharvey2
            That is welcome news. I read in some remote corner of the Glen-L website that to get SHP from BHP multiply by 87%. That is quite a loss.
            Message 5 of 5 , Jul 24 9:10 PM
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              That is welcome news. I read in some remote corner of the Glen-L
              website that to get SHP from BHP multiply by 87%. That is quite a loss.



              --- In AtkinBoats@yahoogroups.com, "alankornhauser" <alkorn@...> wrote:
              >
              > Gears are very efficient. According to Mark's Handbook, the efficiency
              > of single reduction spur gears is 93-96%. Since most marine gearboxes
              > are single-reduction, this means that SHP is almost identical to BHP.
              >
              > If you think anything on a boat is designed to better than 7% accuracy,
              > think again!
              >
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