Water pump impeller styles?

Mopar92 said
I always understood cavitation happened at a higher speed. Any impeller. Or propeller.

That is true, and the less blades the higher RPM can be without cavitation.
In my own case I felt I need more blades for more volume at lower RPM's.

Mattax said
Yes.
Sealing off the back should reduce the cavitation.

If running straight water, there are a few products on the market to improve its heat transfer characteristics. I'm not sure if they change the conduction property directly or work more on the viscosity to improve heat transfer. Some include corrossion inhibitors - which is important, especially on a partially open system.

The products like Water Wetter have an ingredient that lets the water make better contact to the metal inside the engine so the coolant gets more of the heat transferred to it.
They use the words "surface tension" properties to describe what it does.