Not All Coolants Are Created Equal
Avoid costly mistakes. Make sure the people dumping coolant in your heat exchanger know what to use and how to use it, and always use the manufacturer's suggested coolant. This is what happens when non-compatible coolants are mixed. It crystalizes and turns into a sludge. A small $ mistake in the choice of coolant turns into a big repair that will shut your boat down and cost hundreds or thousands to get right.