How do you change coolent on mercruiser 8.1?

To change the coolant on a MerCruiser 8.1 engine, start by ensuring the engine is cool and then remove the drain plugs located on the engine block and the heat exchanger to allow the old coolant to drain out. After draining, replace the plugs and prepare a mixture of fresh coolant and water according to the manufacturer’s specifications. Use a funnel to fill the cooling system through the heat exchanger, and then run the engine for a few minutes to circulate the new coolant, checking for leaks. Finally, recheck the coolant level and top off if necessary.