JKnox - while fairly new to this TF group, I am not new to Willards. I own a 1970 W36, and am moderator of the Yahoo! Group Willard Boat Owners Group that has been around for 20+ years. As you can imagine, blisters have been extensively discussed over the years - perhaps 100's of posts with extensive research on mil-spec driven changes to resin formulations, etc. Feel free to come over and join. All Willards at the time were semi-custom, meaning they weren't built until there was an owner.
In very general terms, blisters come in two flavors: below waterline, and above waterline. In my observation, above waterline blisters are mostly associated with late 1970's early/mid 1980's, and associated with changes to resin - there are a number of Willards of this vintage with moderate above waterline blisters (versus severe case of pox that looks like an inverted golf ball - Uniflite). Below waterline blisters are very common - vast majority of Willards of all vintages have/had them, including mine (at least 100). I received a survey credit when I purchased her, I will pass that along to the next owner when she sells. Simple. I do not know of a Willard that has had any structural damage due to blisters.
These are relatively thick-hulled slow boats. The only downside to blisters I can tell is when you haul and Capt. Obvious comes up and say "Gee, your boat has blisters!"
Blisters are a non-issue for me as long as the valuation reflects a respectable credit so I can pass along during resale. I will go a step further and say that anyone who is very concerned about blisters should not buy a fiberglass boat let alone a Willard. Weebles, my W36, currently sits in Ensenada undergoing a full refit where I can have a full bottom job done for a very reasonable cost. I won't do it as there are better places to spend my money. But that's me.
Good luck with your sea trial.
