My yellow '81 Hobie 16 hulls looked just like yours.... they now look like new.
1. Get some bar keepers friend cleaner for $3 and scrub off all the grime. Let that stuff soak 10 mins keeping it moist. Repeat a few times if you have to. You want your hulls super clean.
2. Wet sand your entire boat with 800-1000 grit automotive sandpaper. Yes you will see milky yellow water as you go. no big deal. Oxidation removal.
3. Wash and dry the boat - make sure its spotless to the best you can.
4. Buy a gallon of ZEP wet look floor finish from home depot ect for ~$20
5. Apply a minimum of 5 coats with a sponge allowing 15-20 mins between coats.
BEFORE:
AFTER: