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[markhpc]

I hate to continue this thread since I feel it has a 96.7% chance of being a hoax but....

I find it hard to believe that the linked moisture meter can actually scan through typical marine-thickness fiberglass? Have you used it on the hull or just inside the engine room on non-glassed surfaces? Seems like that thing is way too affordable but maybe I'm too skeptical

I read through a number of threads on thehulltruth and boatersed before I settled on that model. I don't remember the thread, but I believe there was a user on one of them that followed their surveyor around to compare the readings vs the surveyor's meter with moderately close results. I wouldn't strictly trust the percentages shown, but it has been very effective at mapping out gradual changes in moisture over an area like along a stringer or across a deck. Hulls and Transoms have been trickier, though I'm feeling more confident lately than I did when I started.

I'm a firm believer that you shouldn't trust a single tool though. I have a FLIR thermal imaging camera, my moisture meter, and I've tried to learn how to sound out and sometimes feel the differences between wet and dry stringers/decks/hulls. Wet coring sounds different and feels different. For a deck I'll start out with my thermal camera and if I see a temperature gradient I will hit it with my moisture meter. Often times they agree with each other. I'll tap on it, I might try jumping up and down on it where it looks worst. If I don't see any gradients with my thermal camera I'll try to hit up common problems areas with my meter. Near the windlass, near stanchions, hatches, etc. On the hull I'll look at through-hull fittings, areas on transom near where stringers intersect. I'm in no way an expert, but I've looked at somewhere around 20-30 boats at this point and I feel like I've gotten a pretty good feel for what things sound and feel like and when I can trust the meter/camera results and when I can't.

FWIW, I definitely do see false positives both with my camera and with my meter. The camera can easily show anomalies from reflections and the meter can have problems if there are different kinds of materials under the surface. The way I try to look at it is that these tools help me find potential issues but don't necessarily tell me that there *are* issues. The more tools and methods I have that agree with each other though, the more confident I feel that I'm seeing something real.

 

[markhpc]

Here's a photo from my thermal imaging camera of a wet side-deck on an old 1980s carver mariner after it had been sitting out in the sun for a while in the morning. That area of the deck doesn't show any cracking, but if you bounce up and down on it you can feel some of the bounciness from the wet coring in the deck below. If I stick my meter smack dab in the middle of that it registers a 100% reading and will beep madly. As you move away from the center the meter will gradually lower down, though if I recall in this example I was still showing 40% even in areas where the camera makes it look "ok". Typically in dry areas of a deck I might see a 10-15% reading.

Stringers have been more complicated since the thermal imaging camera is basically useless. Instead I rely on my meter, soundings, visual inspection, and if I'm lucky, finding a limber hole or gap somewhere I can try to shove a paperclip or a key to see if it pokes through the wood.