Jesse,
I haven't installed them myself.  It was on my "before she goes in the water" list of things to install.
There is an alternate solution that would work for you.  An in-line check value would allow the same type of protection without holes in the hull.  

This one works for both 1" and 1 1/2" drain hose.https://amzn.to/2Rz4XSX

James
    On Sunday, December 8, 2019, 07:34:55 PM CST, Jesse Shumaker <jesse.laten.shumaker at gmail.com> wrote:  
 
 James, I looked a bit more at the one way scuppers online and it appears that
they install on the outside of the hull and would need to be attached with
screws.  I'm reluctant to add any holes to the hull below the water line for
the mounting screws.  Did you add a one way scupper to your boat?  If so,
could you mention what model and how you installed that?  Thanks



--
Sent from: http://rhodes-22.1065344.n5.nabble.com/