Interesting – have not heard or seen vented loops used this way. My 34 does not have them and no problems in 40 years
John Read Legacy III 1982 C&C 34 Noank, CT From: CHARLES SCHEAFFER via CnC-List [mailto:cnc-list@cnc-list.com] Sent: Wednesday, June 29, 2022 5:20 PM To: CNC boat owners, cnc-list Cc: CHARLES SCHEAFFER Subject: Stus-List vented loops Learned the hard way how to test vented loops. I was changing engine hoses and came upon an original, 33 year old, bronze, vented loop for the engine cooling water. It's located between the heat exchanger and the injection elbow of the exhaust riser. It's purpose is to break a siphon and prevent water flooding the engine and the boat when the engine is off. Mine was filled with scale and no longer operational. The following comes from info included with a new Forespar vented loop. To test a vented loop, you blow air through the vent from outside into the tubing, through the "duck bill" rubber thing, and that's it. If air won't penetrate, it's clogged and should be cleaned. If the thing leaks, it probably needs cleaning or a new rubber duck bill. I replaced the Forespar rubber duckbill, $15, on my bilge pump hose and I replaced the entire loop fitting $44 on the engine hose using a Forespar 5/8" vented loop. Now both of my vented loops use the same duckbill vent and have the same size retaining nut so a simple clear two foot length of 3/4" hose can be pushed over the fitting to facilitate testing either vented loop. I have to add that I never had a problem in twenty years of ownership and ingnored these items until I started replacing hoses. I'd be glad to hear anyone else's ideas on this. Chuck S