cooling circuit problem

[calanque550]

good evening all

Posting from France, excuse my technical english.
My problem is that after having run in very shallow water my 50 EFI outboard engine probably took some sand very fine dust.
Since that i have only small drops of water exiting the hole on top of the engine ( is that correct you call it " piss hole " ? )
How can I be sure my water pump is OK, if yes, how can I flush the circuit to clear it.
there is no professionnal near me, and my boat is at float.

Many thanks in advance

[boats.net]

Need to remove hose from tell-tale nipple in cowling and check to see if plugged up.

[Utiketlesstup]

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