It's "normal" to have blue gelcoat come off, yes. Is it injuring? Probably to some extent. The process of removing oxidization is also removing some of the oxidized gelcoat. The gelcoat is already damaged so you have no choice to restore it, however it is removing some of the gelcoat and eventually you will wear it down to the underlying layers of glass.
With that said, welcome to the Macgregor blue hull. When it oxidizes, it looks bad.
I have always used a 3M product to restore the color. However, they don't seem to sell it anymore, so this year I went with a new product.
https://www.amazon.com/dp/B00029CYRG
This stuff worked great.
My system uses a buffer polisher with a wool pad
https://www.amazon.com/dp/B004W1WGIC
https://www.amazon.com/dp/B09PRRW643
It's a good investment. The wool pad turns blue....very blue. But it washes out and is reusable.
The result is a bright shiny blue hull that looks new. Don't press too hard as you ARE removing some of the gelcoat.
This will leave your hull looking great....but wait...won't it just get messed up again? Indeed. So we need to protect it.
Next tool you need is a dual action polisher. (works great on cars, trucks, anything)
https://www.harborfreight.com/75-amp-6- ... 56367.html
I use a microfiber pad to apply
https://www.amazon.com/Jescar-Power-Pol ... B076ZWMD2G
This stuff is amazing. Goes on easy. Let it sit for 30 minutes to bond with the surface then simply wipe off with a microfiber rag.
This is what you are left with.
The Jascar product is the best I've found. It helps prevent spots by not creating water spots but sheeting water off the surface.
This is the result.
