I am in the process of buying my first sailboat, a 1990 Catalina 42. The boat will be hauled pretty soon to be surveyed, and I'd like to know how I can go about determining if there's moisture damage. If the boat is hauled in the morning, at what point will it be possible to evaluate the hull using a moisture meter? One of the surveyors I have spoken with has instructed me that he will not be able to use the meter on the parts of the hull beneath the waterline. However, he says that he can use it on the topsides and deck and check the hull for possible delamination by other means. Do you think this will address any possible water penetration to the hull?
Dan Dickison responds:
Thanks for getting in touch with us regarding your potential boat purchase. Unfortunately, you're apt to get a slightly different explanation from every surveyor that you speak with on the topic of moisture meters, but we think your guy is correct. If the boat you're considering has just come out of the water after being there for a long period of time, say more than several months, it's almost certain that some water has penetrated the paint and likely that some has reached and perhaps penetrated the gelcoat. So using a moisture meter below the waterline on a hull that's been freshly hauled really won't offer you much useful information.
We'd recommend that you go ahead and let your surveyor do his work on the topsides and the deck with the moisture meter, and then use whatever other means he is accustomed to for determining whether or not the boat has any delamination or water penetration in the hull. If he's experienced in the trade, he'll probably learn quite a lot just using his sounding hammer.
On the topic of moisture meters, remember that these devices are set up to measure changes in electrical resistance. So it's really important that the person wielding this tool knows how to use it. If you simply place the moisture meter on the hull and it registers different values from one spot to another, it might be detecting the presence of a metal water tank inside the boat, or perhaps some standing water in the bilge. You can't just read the meter on the outside of the hull and assume that it's telling you that the boat has water damage because there may be mitigating factors inside the boat that otherwise explain the variation in the readings.
Good luck with the survey and the purchase if you get that far.