93 XP 650 to 720 problem

[stap007]

I installed a 720 short block to replace my blown 650. Used orginal carbs and exhaust from the 650. Starts and seem to runs and rev up fine on the trailer with the garden hose hooked up. Put it on the the water,startes and idles fine but no acceleration,10-15 mph. Cloud of white smoke follows me around. Burning water? The cooling hose hook-up is different for a 720. Anyone do this engine swap? How did you route the cooling hose water intake? To the exhaust pipe first then out the right rear of head like the 650 or water intake on left rear of head then out right rear.