My new to me 2016 209 with a Yamaha 200 has what I have been told is an engine flush inlet mounted in the starboard splash well. The fitting that goes on the hose clicks into it securely but no water comes out of the engine with the hose on. Normal flow is visible with the engine running. Is it likely one of the fittings is bad? Or some sort of plug in the hose? Or am I doing something wrong.