I have a 1997 Yamaha 150 pro-v with a 25 pitch prop (can't find make,)5 inch jack plate on a 1983 Ranger 350-v. I am only getting 52mph @ 5000rpm wot. Motor is setting 3.75" above transom and as best as I could measure cavatation plate is 1-2" above step on transom. I have a slow hole shot...