Boat is 6 years old now and my prop has a couple nicks in it.  It’s stainless, I’ve been careful but have ran ground 2 or 3 times over the years.  It has some nicks and dings but nothing serious.  This year I noticed I’ve lost about 2 mph at top end, used to be able to hit 40 but now top out at 38.  So question is at what point should I be considering fixing or replacing?