I had a 131/2 X 25 4 bladed prop that was slow to get up on plan but would run the boat about 60mph. I put a 12 1/2 X 23 5 bladed on, get on plan fast but can only get about 47 mph at a lot higher rpm. What would you suggest. Also I have a 9" jack plate and have never change the setting on it. The 4 bladed prop makes my boat porpoise at low speeds.