Gelcoat Repair Tips

Gelcoat Repair TipsGelcoat Repairs

Repairing Gelcoat


During our recent Seminar, Norton’s Marine Service Center’s Yard Foreman, Sid Simmons discussed some of his tips on Gelcoat Repairs for star cracks in your boat.

Gelcoat is a Polyester Resin with Pigment in it. This means Gelcoat will not flex like fiberglass because it is a lot more brittle. There are various types of gelcoat repairs, but star cracks are the most common. They are caused by impact or stress, and when left to the elements, moisture can penetrate. In colder temperatures, like we have had lately, that moisture can freeze and make the cracks even larger.

When repairing gelcoat, it is always important to remember to wear appropriate eye and skin protection, like gloves and safety goggles, because gelcoat requires methyl ethyl ketone to activate, which is highly caustic.


To begin the repair, you will want to Dremel out v groove shape to the area.

Then, scuff sand with 400 grip.

Tape around the area and put down extra masking plastic to protect the area that does not need repair from what may be on your hands, feet, etc. Sid prefers to use 2 layers of tape and plastic around the void.

Wipe down the area with acetone.

Create a paste with your gelcoat and Cab-o-Sil to get a constistency of butter, then use a squeegy to fill the void in.


Block sand the fillers and then prepare them for spray by covering around the area with masking plastic, an using foam edge tape around the perimeter to give a feathered edge to final result.

Gelcoat Repairs
There are two types of tools to use for spraying:

A PPS System consists of a collapsible bag with an O-ring that sits inside a cup and hooks up to a siphon feed gun. The gun compresses the bag up to get every last drop of spray.


Another option is a Preval Sprayer; however, this will Gelcoat Repairssometimes leave little craters in your final product due to propellant.






When spraying, it is important to not over-catalyze your gelcoat. Catalyst Oxidizers will yellow, and most white gel coats contain blue pigments to give a brighter look. When over-catalyzed, the blues mix with the yellows, and you will end up with a green spot on your pretty white boat.

Once you have finished spraying, you will just clean up the area with acetone.


When it comes to serious repairs, like that on non-skid, it takes some serious patience and art. We do not recommend battling this type of repair on your own because it could drive you mad. If you are looking to have any gelcoat repair done, Sid Simmons is a master at what he does, and you will not even know it was ever there.

We also would like to point out that while doing work on your own may save you some money and give you a sense of accomplishment, we have seen situations where a quick fix by the owner resulted in major bucks in repairs down the road. So the best option is to leave it to the experts. Give Norton’s Marine Service Center a call the next time you have a project: big or small.