Hope you guys can help me figure this out! I have a 2003 merc 150 xr6 CARB motor mounted on a 1994 hydra sport 1900 flats boat. I changed the thermostats,poppet valve,temp sensor for the gauge, new water pressure and temp gauges,spark plugs (yes they are the correct ones) and did a complete water pump kit, all parts are from mercury, I have had this problem before I did all this work (also back flushed the cooling system with a water hose and found nothing),inside of the heads look clean. I also rinse the motor with salt-away everytime and after every use. Compression is 124-125 in a 6 cylinders. The motor runs 180 to 190 degrees or so at WOT and 160 165 at idle (I also checked it with a laser temp gun just to make sure my gauge is reading right and it is) the temp warning alarm has never come on yes i checked it to make sure it works . My water pressure is good (3-5 at idle and 11-13 WOT). I also went from a 19p prop to a 15p prop and that didnt help any (Stiletto props). I looked at the water holes in the lower unit and they are clean. The motor is mounted at the correct hight on the transom. Im in florida and right now the water temps are 90 degrees.I was thinking maybe the timing is off but looking at the timing screw it doesnt look like anybody has messed with it (factory paint is still alined on the screw). The motor runs absolutely perfect except for this cooling issue. I also used a laser temp gauge just to make sure my gauge was right and it is. I need to get this fixed ASAP I have tournaments coming up. Also I changed the water pump and poppit twice thinking i may have messed something up but same results. I also tried gutting the thermostates and cutting 1 coil out of the poppet valve spring still no change. It only runs hot in the summer time in the winter or cooler outside temps it will run 150 160 degress. ANY help would greatly be appreciated!!!
