ORIGINAL: sportygreg
It looks like you are using plastic tubing to cool the motor-does that work well?
I do not think the plastic tubing will conduct the heat between the water in the pipe and the motor (I use the aquarium tubing also for my plumbing to my motor coolers)
Try using aluminum pipe around the motor it will work better
PS just do not put Cadillac on your boat cause it will spend more time in the repair shop than on the water