if you have fiberglass tanks ill only say this once... replace them with aluminum for your safety and the safety of others. todays fuels break down fiberglass tanks and can cause leaks, as well as damage to your engine by boating your motors parts with broken down resin. aluminum tanks can be found on craigslist, etc from anywhere between $100-400 depending. they will last forever.
at any rate if you have typical fuel fills like these, then the top is spring loaded and they self vent:

you should use uscg approved fuel fill hose. you wont need much but it runs about $20 a foot. heres what my original hose looked like, cracked, leaky, and brittle:

new:

and the new fuel fill hose, double clamped at both ends with stainless hose clamps not autozone cheapies.

its an easy job and they'll last FOREVER after that and be safe.