Laser hull discolouration

If you are careful you can sand out most abrasions with 600-800 them finish with 1200 before polishing. This will be much faster than just polishing it off, with the tradeoff that you do need to take more care. Provided you are careful you will remove no more gel than the polish only method as all you want to do is remove the discolouration.

Obviously you could hit problems if this has been done before, so on an old boat i would check carefully before proceeding. If you shine a torch directly onto the hull in a garage or shelter you will be able to see very fine sanding marks that polish does not quite remove. You do need to get the light just right for this, but they look very different to scratches due to use and are a dead giveaway that someone has had a go before.

The discolouration is more than likely due to UV, though i have seen a couple of boats that have changed colour due to damp being held behind something stuck to the boat. These have always been dark colours and you have to wait a few weeks/months for the gel to breathe the moisture out. This is also more likely where a chart has been taped on rather than a sticker which is adhesive. One boat with this problem returned to its original colour over the summer.