I had problem with 2000 - 90 yamaha 2stroke overheating as soon as I ran it up to 4000 rpm..... finally ended up replacing the thermostat and pressure control valve. I noticed that the Pressure Control Valve that I took off looks different from the new replacement . Is this an improved design? This finally fixed the problem that stumped the mechanic. He had replaced impeller and took apart the water jacket costing me $. I replaced the thermostat and pcv myself from advice on this forum and the motor runs great now.