scrap any one-way valve or similar gadget in the anti siphon, and leave a 1/8" or so hole to pee out where you can see it.
Most boats can run it into a cockpit drain where it is visible without being a nuisance.

With a constant flow, it is VERY unlikely to plug, but if it does, you can see it. Hopefully will notice declining flow as the salt and crud build up.

We originally had a 1/2" flap check valve, thinking it wouel not plug. However it did, and filled our engine.

We knew same day, and first spun it a lot with the valves lifted, then made sure it turned by hand, then ran it.
Then about 4 oil changes in a couple of hours light running.

That was about 2000 hours ago and the engine is OK

Ther ahve been previous threads on this problem, and the consensus was as above.