First off, I'm new to boating. So go easy on me. Its on a hurricane 187. At full throttle I can only get the rpm up to 4500. I bought it gently used (40 hours) and now have about 60 hours on it. The wet test it got 5200 rpm and 40 mph. Since then the speedometer broke but a downloaded app says I only reach about 27 mph. Any ideas would be greatly appreciated.