Are Bottom Blisters on a Boat Something to be Concerned About?

There are two schools of thought on bottom blisters. Some people absolutely refuse to accept a boat with blisters. Other people feel they are a part of life when you have a boat in saltwater and they don’t effect the operation or performance of the boat. If you have or are considering buying a boat with blisters and you want them gone the first step is to blast off the thick layers of old antifouling paint. After the bottom is stripped if there are obvious bumps in the gelcoat they should be examined to see if any liquid is seeping from them. If there is, your yard should have recommendations for more serious measures to repair them.

Often blistering issues can be attributed to the original fiberglass layup in which the layers of mat were not applied correctly or inferior materials may have been used. This can result in a hull with a hidden layer of mat that is full of dry spots that have not been saturated with resin. Over time the gelcoat becomes permeable to water and the unsaturated spots may become blisters. Often this results in just small areas of dry glass and not the more troublesome weeping blisters. So where do you go from here if you want to get rid of those blisters? Usually the yard will blast, machine peel, or grind until they reach healthy material. If it is dry (which it often is) they will then coat with several layers of epoxy based barrier coat to prevent the same problem in the future. However the yard should still use a moisture meter to determine the moisture content of the remaining fiberglass. If the yard you are working with doesn’t do this then see if you can call in an expert who can. Remember the hull should be completely dry before applying epoxy barrier coats and if you end up working with blisters that are weeping be sure you are dealing with a yard that has experience in this more troublesome situation.