My boat is a 1995 Rinker with a 5.7 Mercruiser carb alpha 1 gen two. It has 550 hours on the clock. Is there a recommended interval where the water pump on the engine should be replaced as a maintenance item before the engine overheats? Looks like an easy job to do and the cost is reasonable as a DIY. Is there a way to know if the pump has been replaced already?