We have a Beta 60

Beta UK recommends about 50% antifreeze in the coolant, but youi advised me at Annapolis that 35-40% is better in the tropics

We are in the S Caribbean, and due t change coolant.

Antifreeze is hard to find here.  The locals  use either plain water, or stuff like Herrero's Red cool, which is described at their site

http://herreroandsons.com/cgi-local/products.cgi?category=28&subcategory=79&subsubcategory=&product=1025&mode=show_detail

Teh RedCool blurb says

"Specially formulated for tropical temperatures.
A genuine corrosion inhibitor that protects steel, cast iron, aluminum, solder, copper and brass. Harmless to rubber hoses, water pumps and gaskets."

What do you think I should use  in the engine