Had similar condition on 14ft Monark. I used a product called Aluthane with great results. It served as my base coat.
Sold by a company in New Hampshire at this website https://www.epoxyproducts.com/aluthane.html
It is used on bridges, grain bins and several boat examples on site.
Costly perhaps $80 per gallon and you need to use it all up or risk it hardening if stored. I lined up several items that needed painting and prepped them as well.
It may be more than you want to spend but thought I would share the solution that worked for me.
I was very pleased with how it covered and adhered to the boat and how final paint job adhered to it. Not for sure but it appears to have helped greatly with any possible leaks as the boat has Zero leaks at this point.
Hope this helps and good luck.
Ken Q