Im just wondering why all the high performance boats I look at have open cooling instead of closed? If I had the money for a nice boat with expensive motors I wouldn't feel too great knowing that salt water was going through them, and knowing how it shortens the life of them too. Yes I know you can flush after every use but it's not quite the same to me.

Is closed cooling just too restrictive and cause overheating issues?

I would imagine a couple of reasons

1. if you are even halfway taking care of your boat and engine (and actually using it) you will need an engine refresh long before you have issues with salt water going through it long term

2. the desire to not have to carry cooling fluids or have a tank for cooling fluids.....although the new 7Marine outboard manages to have closed loop cooling and it is an outboard with no external tanks of any type (other than fuel obviously) but at the same time it is actually not really a "high performance engine" since it puts out the exact horsepower that the block (and rest of the engine) is built for right from the factory for every day long term use in a street car with a warranty

I have closed cooling on my Baja. I love it. I run in both salt and fresh water. No worries about the aluminum heads and very easy to winterize.