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Waterpump & Thermostat Maintenance


The question of when to replace a water pump has been asked by many boaters over the years. The answer is not as simple as one might think. You need to take many things into consideration when answering this question.

The first response to that question is, “When was the water pump was last changed?” The reason for this question is to get a baseline of maintenance that either has or has not been performed.

Often, the question is asked by a boater who has purchased a used boat. They have no record of service performed. In this scenario, I usually recommend that it be replaced. Allowing us to establish a new timeline of maintenance.



  • There are many variables related to water pumps and thermostats.These are just a few:
  • Can you see water coming out of the telltale port?
  • Has the motor recently overheated?
  • Have you been boating in shallow water?
  • Do you take your boat to beaches or sandbars?
  • Has the motor been started out of the water?
  • If the question to any of these answers is “Yes” then it may be time to service the water pump.



When performing this service it is not advisable to only replace the impeller. All components should be replaced. Only replacing the impeller could lead to premature failure. Correctly installing new components, such as new gaskets, ride plate, cup, impeller, bolts, & drive key will ensure good water flow and longevity of the cooling system. The water pump and thermostats should be replaced at the same time. They are crucial to the proper operation of the engines cooling system.



Thermostats regulate the temperature of the engine.  Thermostats become clogged, or corroded, and cause an engine to overheat and possibly seize. This may cause damage to boat’s head gaskets. Thermostats that are stuck in the open position prevent a motor from reaching proper operating temperatures. This will affect performance, fuel usage, and will cause spark plugs to foul pre-maturely.



Typically, water pumps and thermostats should be serviced every two to three years. This varies on where you do most of your boating. Also, whether you rinse out your motor after every use could make a difference.