- Oct 6, 2006
- 12,156
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
I should probably wait for the photos, but the part of the coupler that is on the shaft is keyed. I suspect that you are seing the keyway that is milled into the shaft to accept the key for the coupler.....it just extends up the shaft a ways.