I have a 2003 75 HP Yamaha 4 stroke outboard that appears to be overheating. Last year it overheated and melted a part. I had it fixed by boat mechanic who replaced the part but when I used it again the shroud was very hot to touch. This Spring I put in a new thermostat and the engine is peeing a good solid stream from indicator yet after 15 minute ride bonnet is too hot to keep hand on it. Any ideas? Please help!! Thank you!