Sounds like those little wasp have laid eggs in the tell tale and then sealed it with mud. Take a small piece of somewhat stiff wire and dig the dirt out of the tell tale hole. The flush hole is for purging any salt water out of the motor before putting it away. I doubt if you could get enough pressure to force that dirt out once it's hardened but you could try.
update. it was fine. It was only running on one cylinder. I've spent the last 8 hours trying to get good spark on both cylinders. Sure aint as easy as an OMC magneto. Getting rid of it.