Your motors serial number will verify what you have and it looks like your motor has the troublesome lip seals. There was a mid year change on the seals and the earlier ones were the carbon/O ring style which were replaced by the lip seals. Somewhere down the line OMC realised the lower lip seal wasn’t cutting it and they went back to the carbon style seal.
I can’t find an RD 17 parts manual but this ’55 Big Twin manual shows the difference between the two styles of seals and whereabouts in the serial numbers it happened. At least for the Evinrude Big Twins.
55-Evinrude-25-hp-Electric-Parts-Manual
Here’s are ’56 FD and a ’56 RD lower lip seals as found when the powerheads were removed.
