Thru-hull flapper check valve?

[JVallely]

I've read in several places about the idea of putting a flapper valve at the diesel exhaust hose outlet to prevent sea water ingress. I want to do something similar with my exhaust hose and with 2 additional cockpit drain hoses I want to install.
The only flapper check valves I see online appear to attach to the end of a hose with a hose clamp. How do you mount a flapper check valve to a through-hull? Or is there one that will go inside the hose or the thru-hull fitting?
Any leads would be appreciated.
John V.
Alajuela 33
Selkie

[Capt Len]

Real flap valves are bronze and NPT which means threaded pipe fittings. They are gravity operated so placement is important.(heeling may open it) . Common exhaust flapper on small vessels is external on the transom Personally, I have trouble with trusting any 100% Proper sea cocks must be on any thruhulls ,flappers are secondary I like an RV type plastic blade valve inboard the exhaust port.They easily fit the existing hose and are push/pull operated.So if you can reach it or the extended handle its good peace of mind. As an aside, I installed a ball valve in the aqualift muffler to insure that any failure of salt water stuff doesn't get to cylinders, Mine works off the key but manual is good if you remember when open and close should occur.

[VallelyJ]

Thanks for the reply and thorough explanation, Capt Len.
I want to add a couple 2" or 3" cockpit drains with hoses from the aft end of the foot well to new through-hulls in the canoe stern just aft and below them. The existing arrangement of 2 standard 1 1/4" drains seems inadequate. My search for externally-mounted flapper valves started there. I figure that if one fails somehow, I'll get wet feet but the boat won't sink.
I then thought to add a flapper to the exhaust while I was at it, since I have nothing there now but a high loop. A bronze fitting for the exhaust would be ideal, but will have to wait for the budget to catch up. A seacock is another thing I've considered.
John V.

[Capt Len]

Unless you are getting pooped regularly or its a huge cockpit, two 1 1/4 drains seem like enough. Your call. The exaust flapper can be as simple as a piece of old rubber fender screwed on over the outlet Its natural springyness holds it shut . The plastic bayonet type rv valves I mentioned are good value and fit directly into exhaust hose at the transom. Shut in emergency or when sailing down big swells .Boats like Yamaha 's and others often fill their engines even on a nice day.Sort of like if it can go wrong it will.

[CorvetteGuy]

We uses a plastic goose neck right at the thru hull for the exaust this also came with a water trap at the lowest part of the exaust system works great no water where it shouldn't be (on top of pistons)

[casey1999]

West Marine eCatalogs

Take a look at the top of page 664 of west marine catalog- see if that is what you want (link above).

[casey1999]

Originally Posted by Capt Len

Unless you are getting pooped regularly or its a huge cockpit, two 1 1/4 drains seem like enough. Your call. The exaust flapper can be as simple as a piece of old rubber fender screwed on over the outlet Its natural springyness holds it shut . The plastic bayonet type rv valves I mentioned are good value and fit directly into exhaust hose at the transom. Shut in emergency or when sailing down big swells .Boats like Yamaha 's and others often fill their engines even on a nice day.Sort of like if it can go wrong it will.

Could you post a link to this plastic bayonet type rv valve?
Thanks

[mitiempo]

One of the flapper valves from West Marine - I think it would work.