As halekai mentions, not all hose clamps are created equal. When reading the box for any brand one will note that, "stainless steel band" is not the same as saying "all stainless steel". Most clamps use somewhat deceptive marketing to hide their cheapness in quality.
Elbos with one size up for hose fittings are a really good idea if you have to use elbos. Try not to if you can. Sweeping flows better and clogs less. Of course, on a boat, it's not like you have too many options given the space considerations!
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.