Generally speaking, there are three reasons for this problem. The first reason is the cooling water passage was blocked, so you should check whether the outlet of the outboards has normal water current. We recommend you change your impeller every year at a minimum depending on the amount of use you put on your outboard. One thing to remember is that even if you only use your outboard a couple of times a year you still need to have your impeller checked/replaced every year. Water pump impellers are made of rubber and will deteriorate over time even without being used (commonly referred to as "dry rot"); this can be just as damaging to your water pump as wear and tear.
The second reason is that the oil is too short. The last reason is that the end users start the engine out of water and then make the water pump to be damaged.

2016-07-13

Why it is very difficult to start some outboards after storing a period of time?
Do Parsun outboards come with lower unit oil (gear oil) already installed from the factory?

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Why some outboards will overheat while running?

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