My Wooldridge Sport with a 115 Yammy came with two 7 3/8D Aluminum impellers, and my max RPM was 5K. My old Alaskan had stainless impellers, so I never really did experience the difference between the two on the same engine.
So, I recently picked up a Stainless 7 3/8 D for my Yammy, and my max RPM is 5200 now, with what seems a slight loss of top end speed, but quicker on step. I thought it was shimmed perfectly, but it was rubbing a tiny bit on one side, so I need to remedy that.
Does this slight increase in RPM at WOT sound normal?