I have a '90 Arriva 20' With the 5.7(260hp)Merc. AlphaOne and through hull exhaust.When I got the boat it had a 21p ss prop. It took forever to plane out,wouldn't turn over 3300 RPM and topped out at about 30mph. I had to drop down to a 17p prop. Now it planes out a bit better but but still only runs about 43mph at 4900rpm . Does anyone have any Ideas on what could do to get better performance out of it? I just thought it would run better than it does. This my 1st boat and any help is appreciated .