Looks like an Apollo ball valve...not a flanged seacock. Marine
how to has some nice videos on the subject. The green color is not an issue as explained above.
All stainless clamps are not equal in strength. I never use slotted.
Please post more photos and info on exactly where all these openings to the sea are located and where the pipes go to.
You can get a free survey
here which is sometimes better than what people pay for...just post and ask how to improve things.
Happy trails to you.
Mark and the manatee crew.