My 96 yamaha 150 picked up some sand today and my pee hole kept clogging up with sand and small shells. Everytime I went over idle it would clog again and the overheat alarm would go off. I ran clean water through it at home and it had a good hard stream. I also took out the thermostats and they had a lot of shells in them so I will replace them. Can I put the housings on and run the engine to flush any remaining sand before installing new thermostats? Should I also replace impeller and water pump as well? I have never done them before and only owned the boat for 6 months so I don't know the last time they had been changed. After I pulled the thermostat out I noticed pretty good salt build up inside the cylinder head housing. Should I rebuild the cylinder heads or is this normal?<br />Thanks in advance,<br />Mike