Water pumps are a very important part of yearly maintenance as a faulty pump could destroy your engine.
We recommend using a water filter before your pump as it's possible to pick up a gum nut or other objects which may instantly destroy the impeller.
Any extra fittings installed before the pump for flushing the engine must be airproof or this will impede the suction.It's not recommended to run your engine longer than 10 seconds without water going through the pump.
Method of checking A simple test any owner could do is fill up a bucket of water and with the boat on the trailer sit the bucket on the ground, connect a hose to pickup line insuring airtight connection, start your engine and the pump should start sucking water from the bucket.
If this doesn't happen you may wish to pressure feed a bit of water to expel air from the line to hasten suction.
If suction still doesn't occur then maintenance is required.
The life of an impeller could be from 5 minutes to 5 years all depending on care and the situation it is used under.
If at any time you find parts of the impeller broken off and missing it is common for these pieces to become lodged in water fittings and therefore impede water flow after the replacement impeller has been fitted.
The above info is only personal views put forward to assist skiboat owners from Bob at R & M Precision Marine 
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