Boat has nylon thru hull fittings on hull, above the waterline. Think these need be changed to bronze fitting? They are all locker drains, or overboard for bilge and live bait well. Only thru hull below waterline is for raw water intake. That is a bronze strainer.

IMO since they are above the waterline, you will be fine with the nylon. I would just check them every year to make sure they don't degrade because of the sun.

Lots of boats use nylon (my Parker included) above water line!
Below water, NEVER use nylon!

I'd consider changing the bilge pump through-hull to something less likely to eventually crack. Last thing you need is to find out that the boat sank at the dock because even though the bilge and pump worked fine, the fitting cracked causing bilge to just cycle water within the bilge.