I am looking at buying a 1982, 40-foot Island Trader. A recent survey reported that there were five quarter-inch to inch-and-a-half blisters per square foot on the bottom. The surveyor noted that this should be no problem, but they should be inspected at each haulout, and be repaired when and if they reach two inches in diameter. Is the surveyor correct in indicating that this does not indicate a significant problem? And how much should repair of these blisters cost?
Sue & Larry respond:
The occurrence of blisters on fiberglass boats built in the era of the one you are looking at is extremely common. Usually these blisters are of little consequence because they only penetrate into the gelcoat. Many boat owners leave small blisters as you describe untouched for years. However, each case of osmotic blistering must be looked at on an individual basis. If the blisters are deep enough to start intruding into the fiberglass laminate of the hull, you could experience some structural weakening down the road if they're left unattended for too long.
The Island Trader you are looking at likely has an extremely thick fiberglass hull, as many Far East boats of that day did. This will be in your favor. It's very likley that your surveyor has correctly evaluated the depth and current state of the hull blisters, and we think he was wise to say you must keep an eye on this situation.
Boat yards differ in how they charge for blister repairs. Some have a flat rate per linear foot of the boat. We’ve seen that quoated at as much as $200 per foot. Other yards like to work on an hourly basis ($70/hour per person is not uncommon), plus they'll also charge for the number of days your boat is stored in the yard to dry the hull once the blisters have been ground out. We recommend that you shop around and ask for references from other customers who have had hull blisters repaired.
Neither of these options ends up being cheap, which is the number one reason that many boat owners get involved and do some or all of the work themselves. Check out Mark Matthews' article Surviving the Haulout here on SailNet for his first hand advice on blister repair.
You may also want to use this blister condition as a negotiating tool in the purchase price of the boat with the Island Trader’s current owner. Best of luck.