The engine on most sailboats is installed at least partially below the waterline, consequently, with most exhaust systems, the only thing preventing the engine from flooding with water after it stops is the siphon break installed at the highest point in the raw-water cooling system.
That’s bad enough, but the other problem with siphon breaks is that they are usually installed in some inaccessible place, so on a lot of boats they don’t get any love from one year to the next.
This is also made worse because I have never seen an engine manual that calls for regular disassembly and cleaning of the siphon break.
Maybe the engine manufacturers want it to stick closed so our engines will flood and they can sell us new ones…not really, but I do sometimes wonder…particularly when I’m thinking about saildrives, the existence of which clearly proves how much engine manufacturers actually hate us owners.
Sorry, rant over.
Anyway, the photo above shows the state of the siphon break on our J/109 when we got her. Looks to me like no one had looked at it since the builder buried it high in the engine space 18 years before.
I figure that the only reason the engine had not flooded was because the J/109 has a shallow hull form, so the engine is higher in relation to the waterline than on most cruising boats.
Needless to say, I replaced it.