Like a car engine that circulates the coolant every time you use it, so does the marinized version. But there is less coolant being asked to do the same job, with more demands.  Coolant is relatively inexpensive. If you have sterndrives, make coolant changes coincide with the drive (boot) service every two to three years. That’s easy to remember. Also, remember that after you drain the coolant and refill with nontoxic 50-50 coolant, you’ll need to remove the small plug at the top of the thermostat housing so the air escapes and the block fills completely.