[OntarioTheLake]

90% of boats are "maintenance deferred" concerning deck penetrations and saturation. Some are worse than others.

All boats will have some moisture; some boats will have minor rot and delamination that's fixed without too much work; some have been left to rot such that entire sections or decks have no core left.

I know people who sail boats with great areas of core completely gone in non-critical areas; they just live with it. You want to make sure that anything that holds the mast up is either solid or easily repaired.

 

[OntarioTheLake]

The other more serious problem involves cutting out a piece of the deck, and there I would taper the edge of the existing fiberglass and lay in cloth and resin after filling the void.

Jeff

My observations (including our new-to-us boat) is that there are two extents of deck rot: (1) areas where water pools and runs, and has rotted out a section of the deck, often alongside the cabin, sometimes hand (plus-or-minus) size of a foredeck, side deck, or cabin top and (2) wholesale totally rotted core in massive sections.

For example, on ours we have a section of deck that flexes. It is alongside the cabin, about 2/3meter long and 8cm wide. It really bears no load, except me, and no matter how hard I jump I'm not going through the fiberglass. My opinion/ action: I'm going to drill some holes and fill, and that will fill that void for as long as we own the boat. I should note that the leak that caused it has been fixed.

On the latter, with the whole deck core at least saturated, much of the core gone: NO WAY am I going to do this. We passed on my dream boat because of it.


Going back to OP's "1995 Capri 22 " realize that ANY repair beyond drill-and-fill will exceed the value of the boat. So it depends on what you want to do with the boat, and if the rot impacts safety. If sections of the deck and cabin are rotted away, you're not going to race, and the mast base and chainplates are OK, sail it.

@Don L maybe you're right, but I think 20 years is pushing it. Anything OVER 20 years, I'd say expect some wet core- and expect lots of it in race boats and boats on the Great Lakes. OP's subject boat is almost 30 years, and good luck finding something that old with some moderate amount of wet core (or, missing core.)

Now, @Don L does yours not have wet core because it's an awesome production boat, or because you did maintenance? If it's the latter, well you're less than one in ten.

 

[OntarioTheLake]

... meter is reading 30% on a deck section, and I move the meter 10 inches to another section of open deck and it reads 90%+, ..... Very frequently these high moisture areas are around deck penetrations of course, but not always.

Right. And typical.

I can guess when I first get on a deck where I'm going to get higher readings. Then, with some more inspection of the deck, cabin top, etc I can refine my expectations pretty darned accurately, even before I power up the meter.

My Ryobi has different settings, so depending on which I use, I'll get different percentages. What's important is the delta between a dry area and a wet area. Yes, this is influenced by several factors (and some professionals will have plenty of anecdotal stories about solid glass and 25% readings) but the deltas reported by this $100 Ryobi are pretty good if one doesn't rely on numbers but rather "not bad", "more wet", and "crap, this is really bad."

Yes, in many cases deck fittings will show increased moisture, it's to be expected. On our new-to-us boat, I was pleasantly suprised that the Ryobi reported "not bad" these areas; I was disappointed that it also found the "crap, this is really bad" area on the deck by the cabin, but it was only confirming what was to my foot blatantly obvious.

The little Ryobi has been useful for tracking leaks. Is it this stanchion or is it this cleat that's wrecking the deck? I even used it to track a leak that had destroyed a bulkhead to a dodger snap fitting. And I used it to break my heart when it lit up everywhere on the deck of a boat I wanted so bad that I was willing to overlook a lot.

They aren't perfect, but they give you an idea. Sometimes they're wrong. But if used in a general sense, you get a picture of what's underneath.