I use a 12" stainless steel
drywall knife. Use the end of it to get started and then use the blade.
Works great on the hull
too. There is a lot of nasty stuff that will grow on the best bottom paint
in some harbours that do not have "proper" sanitation.
Never would consider using a grinder or sandpaper, quick way to remove a lot of bronze
. End up with an uneven unbalanced prop.