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GeorgeDog 03-14-2010 09:38 PM

Are Moisture Meters for Novices?
A couple of months ago I went to look at a boat for sale. The listing was promising and the pictures looked great. She showed as well in person but then the broker said "wet decks." Not a little bit either, real wet. It turns out this great looking boat had been through survey four times without a sale. That's $3000 spent by buyers with no return other than the knowledge not to buy. That was the moment that I realized that my job was not just to "look" at boats, but to carefully evaluate them for reasons not to go to survey. The first thing I did was read SailingDog's "Boat Inspection Trip Tips" on this forum. If you are a buyer, do yourself a big favor and carefully read this article. The second thing I did was buy a CT-33 moisture meter. I don't want a boat with wet decks, but do I need to pay a surveyor to find out?

Last weekend I went to look at a very desirable boat for sale. It didn't take long know that I wanted her IF she was a sound as she appeared. When it came time to evaluate the deck I started at the bow. The meter read a very consistent (uncalibrated) 9% but then suddenly read higher following a line across the deck. Measuring the location I went below to find I was reading the forward bulkhead. Okay, that is good, at least I can find something I thought. The rest of the large deck and cabin top read consistently 9-10% except the whole surface outboard the cabin on the port side read 12-14%, and a palm sized patch on the starboard side between the forward portlight and the shrouds pegged the meter. I headed below.

This older boat cabin had obviously been kept dry. The cabin smelled dry, the laminantes were all in great shape, there were no obvious streaks and drips, and not a spot of mildew was evident. I suspected the slightly elevated port side readings were nothing and the starboard side would be a plate or something on the deck underside. Opening a locker under the high starboard reading proved me wrong. The locker was dry to a casual inspection with no discoloration or damaged wood, but poking my head in revealed a soaked headliner. Aft of the locker was dry, forward was dry. Just this one small patch of a deck soaked on the underside. I moved to check out the port side.

To port I also found one small area where the headliner was wet but using papertowels and Q-tips I determined that the whole region under the elevated readings was damp behind the headliner. That encouraged me to look more carefully and I noticed that a lot of the wood outboard was quite damp on its back side, something I never would have uncovered otherwise. So what to do with this information?

The caveat always mentioned with moisture meters is that they are only a guide, that it takes a knowledgable expert to interpret the results. In this case I was impressed with the high level of maintenance on the rest of the vessel. I suspect the port side is not a wet deck but probably condensation. On the starboard side I'd guess that part of the problem is water intrusion with the nearby portlight being suspect. Is the core wet? I don't know but tap-tests sounded fine. I think if I'd carefully dried the area on the inside I could have narrowed it down better. In the end it didn't matter bacause the overall good state of the vessel made me confident enough to take her to survey. Specifically, I would be very surprised to find out the rest of the deck had any wet areas. So did the CT-33 actually help?

Yes. I walked away from the inspection feeling pretty good about the decks which would have been a complete mystery otherwise. The meter does find water that is otherwise invisible to routine inspection. Hopefully I won't need to check many more boats that are on the market but I believe I will get pretty good at interpreting the results if I do. Remember, I'm not trying to determine if the boat is a good purchase opportunity-just a good survey opportunity. I think the meter is a big help in that regard.

More importantly I will use the meter to regularly assess whatever boat I end up with. Had the boat this past weekend been mine I would have followed the (damp) bread crumbs to the hidden wet wood. Better to catch water intrusion in the early stages. So I'm sure it will take practice to interpret the CT-33 readings with good fidelity. But can a novice use the meter as very helpful tool-absolutely.

I'm very happy with the $170US spent on this meter.

Good hunting!

sailingdog 03-14-2010 10:06 PM

Thanks for the plug. :D The article is located here.

boatpoker 03-15-2010 04:57 PM

Every time I see a post like this I have to jump in and offer the other side of "Moisture Meter Myths". And no, just be cause I am a surveyor I am not encouraging you to hire in surveyor instead. One of the points of my article is that you do not need to spend the money on a surveyor or a moisture meter. 98% of the time you can find wet decks with a small hammer, dental pick and screw driver. There is a lot of stuff I disagree with Pascoe on, but he got this one right. Check out my article which gives a lot more detail than the one noted above. moisture meter mythology

bljones 03-15-2010 05:06 PM

A moisture meter is a great psychological tool in addition to the data it can actually provide. A moisture meter is like a lie detector- you don't have to know how to use it, just having it visible can often achieve some truth and a lower price. Whipping out a screwdriver and a hammer, on the other hand, can really get a seller's back up.

Boatpoker, this is one time where i will disagree with you as an average boat-buying schmuck. You, as a surveyor, can percussively test a boat without a seller getting too uptight, because, since you have introduced yourself as a surveyor and presented your creds, there is an implication that you know what you are doing. If me, a boat buying schmuck, decides to start sounding a hull a seller is likely going to throw a fit.

boatpoker 03-15-2010 05:39 PM

Surely no one would get upset with the use of a plastic hammer.

GeorgeDog 03-15-2010 05:41 PM

The provided "moisture meter mythology" link is a great example of why I started this thread. It lists so many points of uncertainty that it can make competent people wonder it a meter is worth it. I know I was on the fence about buying one.

My first point is that it did allow me, a first timer, to find hidden water with remarkable ease. I suspect many in the sailing community have the critical thinking ability to make good use of such knowledge.

My second point is that the meter is less ambiguous than the "mythology" link would lead one to believe. It may not be a crystal ball but it is a bit like having x-ray vision. I found that to be very cool (and helpful).

Maine Sail 03-15-2010 06:02 PM

Apparently there are many satisfied customers. Wallace/Boat Poker always chimes in against DIY's owning or using one, so nothing new in this thread.

In a perfect world, we as boat owners would not need them and all brokers would be honest. In this world all surveyors would have a fee schedule just to do specific items such as decks, in a pre-survey " boat shopping" mini-survey. Sadly most surveys will not do this and many even wait to do the decks until the end so you can't walk away from the survey if you're on-site and see that the decks are mush.

I wrote that article because I had seen soooooooo many boaters get screwed by wet decks, and a $600.00 survey they walked away from, only to lay out another $600.00, two possibly three more times before finding a boat.

They are also not a bad tool to have to monitor your own decks. You can map them and then have your own baseline. This baseline map can be compared to future readings to check for any additional water ingress.

In terms of boat bucks $170.00 is a mere pittance in the whole scheme of things in terms of expenditures. It is always amusing to watch some folks squirm at the mere mention of a DIY with a moisture meter, coincidentally, and not surprisingly, it is usually a surveyor.;) Yes, a $9.00 brass hammer is cheaper but please don't show up at my boat with one, unless you are a surveyor, or you'll be asked to leave. You as a DIY though are more than welcome to go over my decks, as a buyer, with a meter.

I have yet to meet many boat owners or brokers who will allow a potential buyer to begin sounding on a deck with a hammer, brass, plastic or not.

Here's what someone who read my article on the CT-33 actually thought.

This came in off my web site via email.

Dear Compass Marine,

I wanted to thank you for your dissertation on a moisture meter for boat buying. I bought one and used it as you described to exclude boats with severely wet decks. My wife and I fell in love with a beautiful C&C. It displayed like new, inside and outside, and the decks seemed solid when we walked on them. The day before we went to look at it my meter came from Canada by post. I quickly went to the marina and began checking boats of friends to get a feel of it as fast as I could.

The next day we went to the C&C with your article. The decks had many areas that locked the needle at max wet. The decks were dry externally, no dew, and I confirmed no metal in the areas of high wetness. Approximately 35-40% of the decks were totally wet according to my new meter. I was unsure of my results being new with this meter so still talked with the broker to get more input.

It was not until after I let him know what I found with my meter that he admitted there had been a recent survey. The result of the survey was that the boat had considerably wet decks.

My wife and I walked away. Three months later I ran into a guy at the marina who had been looking at boats and he actually surveyed the C&C, the same broker never told him of the wet decks or the survey. It cost him over $650.00 to find out it was a junker. My meter cost me about 1/3 of that survey price so I consider it free, like you said. I would have wasted $600.00 on a survey for nothing because the boat showed so well. Brokers are not always honest but that is anther subject.

Thank you for my free moisture meter.


sailordave 01-09-2011 12:31 PM


Originally Posted by boatpoker (Post 581126)
Every time I see a post like this I have to jump in and offer the other side of "Moisture Meter Myths". And no, just be cause I am a surveyor I am not encouraging you to hire in surveyor instead. One of the points of my article is that you do not need to spend the money on a surveyor or a moisture meter. 98% of the time you can find wet decks with a small hammer, dental pick and screw driver. There is a lot of stuff I disagree with Pascoe on, but he got this one right. Check out my article which gives a lot more detail than the one noted above. moisture meter mythology

Sorry, I have to disgree. Maybe I've got more knowledge/experience of boats than most and that colors my view, but just tapping on a deck w/ a phenolic hammer is NOT going to find all wet decks. A moisture meter will find areas of moisture that you might not find otherwise. And as GD pointed out, there *MAY* be very good reasons the meter registered high besides saturated coring.
I worked in a boatyard many years ago when I knew nothing, I've restored a few small wooden boats, built a few and fixed enough things on different boats I should be in business!:rolleyes:

I will agree that a complete novice w/ NO knowledge of boats/construction would be ill served to think slapping a meter on the deck and buying a boat based solely on the reading is a bad idea. But someone w/ a little knowledge and some understanding of boats in general can benefit hugely from judicious use of a MM.
A boat I sail on has decks that are somewhat wet. BUT, they have not delaminated and *sound* solid when the tapping test is applied. I know this b/c we had some work done and the core was wet but still firmly attached to the skins. We would not have known about the wetness w/o putting a meter on the deck. Period.
I am a big advocate and will use one on any boat I look at for purchase as well as monitoring the decks of any boat I may own in the future. (currently co-own through my small club)

jdmakani 01-09-2011 01:18 PM

I have used both M/M and the sounding method, to work with both is the ideal way and also you have to have a good M/M or you will get false readings that may lead to further problems.

hellosailor 01-09-2011 08:42 PM

Two stiff fingers can go "tap tap" just as well as a plastic hammer. The problem being that many folks are tone deaf and wouldn't know the difference between "thud" and "thunk" if they practiced all day.

So a moisture meter isn't perfect, but the folks who are tone deaf at least have a chance to get some visual indication fro mthe meter dial.

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