salt water ingress

hi learned friends, I am trying to find the source of small volumes of salt water finding its way into the compartments around the bilge area.  Water is found in the blobs shown in green.  I have checked all seacocks, as well as the engine water inlet and the exhaust muffler. I now believe that the salt water must be coming from the transom or rudder stock area, and it runs all the way under the channels shown by the green arrows.  Can anyone help please?

Thanks for your valuable suggestions. My 418 is only 3 years old. The leak does send to coincide with the engine running, but the compartment under the engine and saildrive and underneath the exhaust muffler are both dry. I will check your suggestions and thank you for your help, cheers Dallas 

Saltwater or dirty freshwater, kind of a little orange in color? A common source of water in the bilge with the engine running is the hot water tank over pressure valve. When the engine is on, the hot water tank gets heated from the engine coolant lines that run through it. There is no way to turn that off. The over pressure valve then starts releasing water - into the bilge. You can prevent this from happening in two ways: 1) Harder and more permanent - install an expansion tank on the hot water outlet line from the hot water heater or 2) easier, but a jury-rig, always keep the water compressor off and the hot water tap in the galley sink open when running the engine.