Need Advice
 

I have a 454 in a 23' Warlock. I am getting a fair amount of white smoke from the exhaust pipes. It happens under load, doesn't happen running the boat in the yard. The smoke seems to come from the portside mostly but sometimes equally from both pipes and sometimes more from the starboard side. I just had a new impeller put in the drive (Alpha), I put a new circulating water pump on the motor, a new check valve for regulating water to the risers, and a new thermostat (140). I also pulled off all the hoses on the front f the motor to check for obstructions and force fed water from the garden hose through the manifolds and risers and they are flowing fine. The risers do get very hot to the touch but the temp stays at 150. Any suggestions as to what this could be? I am assuming a cooling problem, but is it?
Thanks: Matt