I have a Chap 183 with a Merc 4.3.
The prop it came with was an aluminum 14.25 x 21 pitch. With this, we top out about 48-50 mph and about 4800 rpm.
We just got a S.S. 14.25 x23 pitch prop. It was able to get 48 mph, but only about 4200 rpm.
Does this sound right, or did I get the wrong S.S...