Re: 1953 Mercury Mark-7 Home › Forum › Ask A Member › 1953 Mercury Mark-7 › Re: 1953 Mercury Mark-7 jeff-registerUS Member - 2 YearsReplies: 1564Topics: 54 December 16, 2017 at 10:24 pm #68688 KG4, KG7 Mk 20,15 & 20. think about it, Rotor has less "robbing pwr" than a heavy flywheel & learn the curve they function quite well,