Hi Steve
I had the same issue with this drain. It clogged often and will eventually rot the lower part the water tank forward plywood protection, which I had to replace. I change the original small clamshell drain with the larger drain fitting used for both forward lockers and enlarged the hole. Easy job, solid glass around that hole and it looks good with no more clogging issues. It should have been the default as there is no way the original 3/8¡± space will let even small weeds and mud pass.
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David Godin
David Godin