I have a 1986 Cafe with TRS drives, 502's making about 600hp. I bought the boat with Hydromotive 25 pitch with 4 blades. My motors are taching around 4,300 to 4,500 at full speed of 70 MPH. My mechanic told me I need to go to 23's but he did not know how much speed I would really gain, other than turning the motors harder since the boat is so heavy. Thanks again for your help.