Volvo TAMD31 syphon break leaking?

[All_at_Sea]

Having just launched the engine runs fine but the syphon break makes an awful noise as it chucks out water which we didn't notice at all last year. Can these things just fail somehow? What is actually inside these things and could it be damaged somehow in the refit?

 

[charles_reed]

Valve jammed, probably. Take it off, soak in fresh water, disassemble and clean, replace with new O-ring and light smear of silicon grease.
It's unlikely to have been damaged in the refit unless some heavy handed person has cracked the plastic or broken a hose.

That's assuming it's one of those (usually blue) inverted U's.
The other popular type has a "piddle tube" coming off the top which should vent overboard through a skin-fitting.