Ok, I have a 2002 Scarab 33 avs with early 496 ho’s with water rails that I about to delete the drain system. I’m confused about the manifolds, I was going to just put a fitting where the check ball is and put the blue plastic plugs there, will that work? What do the water rails do? Do I have to change the manifolds to the newer ones?

Yes, must replace manifolds

There are two air drain actuators. You can delete and remove them, and replace them with 1.25" diameter pieces of pipe. I used to carry a length of pipe in case one of them malfunctioned. There are two on each engine, one starboard side aft, one port side forward. This is what they look like.
But before you delete them, WHY do you want to delete them? Are they leaking? They make a rebuild kit for them.

he is asking about the exhaust manifolds, the early exhaust manifolds had the water rail external to them which you cannot delete you need to replace the manifolds

I understand the valve parts and think they are more trouble than they are worth when they are so simple to winterize once a year. If I’m going to remove them to rebuild them they’re staying off. So the replacement manifolds have drains as well, should I put drain plugs on them?

Are your manifolds aluminum?

Ah, thanks for the clarification.

yes

If you are talking about the ball drain vales for the manifolds themselves, mercury sells a manifold conversion kit 866178A02 for your earlier water rail style manifolds that includes these new 1 way ball valves:

Thanks, but if I delete the drains I can’t use the ball valves. I can barely get to the drains with the motors in and think it was the worst idea ever