|Remove the cylinder head and clean the salt out
|Blow through the tell-tale tube with compressed air (or your lips if you feel you have the lung power). Sometimes it's only a question of the cooling channels being blocked with gubbins, rather than the impeller - it can be a sod to access and replace.
Always clean the engine with freshh water after use as the calts can also clog up the channels and these are tedious to remove.
|check the water pump impeler and intake.