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Q1: how much worry should be given to a survey in which a "moisture meter" show "a high level of moisture" in certain areas of a 2016 150 SUPER SPORT hull?

BACKSTORY
I had a survey done on a 2016 150 SUPER SPORT. A "moisture meter" detected high levels of moisture in the starboard aft side of the hull and the aft half or so of the deck. Moisture was not detected in other parts of the boat. The percussion test also did not reveal any [defects]. There are no visible holes or exposed foam on deck or in the hull.

Based on what I've read so far, I know that water intrusion can [occur] with these boats, and that [water] can potentially saturate the foam (at least if the foam is damaged) and significantly increase the hull weight.

The instrument referred to as a "moisture meter" is not a device that is particularly calibrated to a recognized standard, and "high levels of moisture" are not particularly specific measurements. Measurements with these devices are not exactly like taking your temperature with a high-quality thermometer that reads to 0.1-degree resolution

That the "moisture meter" test procedure produced anomalous results only in two specific areas could be interpreted that something is different in those areas from the rest of the boat's Unibond hull.

For an opinion from a surveyor who has first-hand experience with "moisture meters", read at

https://torontomarinesurveyors.com/all- ... re-meters/

With regard to Boston Whaler boats with their Unibond hull construction, the completely sealed interior of the hull is likely to always contain some moisture as the chemical reaction that creates the foam probably produces water as a by-product. It is also possible that there could be some areas with a bit of uncured resin in the laminate.

A better approach is to make a very careful visual inspection of the hull sides and bottom, looking for any indication of damage or poorly installed screw fasteners holding gear to the hull. Poor sealing of any hole penetration could create an inlet for water.

Similarly on the deck, a very careful visual inspection should be done, again looking for any instance of poorly sealed screw holes or any damage or cracks where water on the deck could seep into the interior.

A hull that has "significantly increased hull weight" will not be floating on its normal lines. However, even a hull that is floating a bit lower than its intended waterline should not automatically be deduced as having retained water. The added weight may be from other sources, like a heavier engine, larger fuel tank, lots of added gear, and so on.

Thanks, Jim. That’s very helpful. Hard to know whether this is a false positive or an indication of a real problem. Unfortunately putting the boat in the water to check the waterline is probably not an option. The surveyor’s educated guess is that there is probably some water in the hull, but not a lot, and that the bigger concern is finding the ingress point and repairing it so it doesn’t get worse (he thinks probably small leaks around the bow railing and deck hardware since there are no obvious holes).

Q2: [have there been any instances] with Boston Whaler boats that are nine-years-old having water intrusion without obvious holes or other damage?

To me this boat is a little young to be having [water in the foam], which maybe lends some support to the false positive theory.

Thanks again,

Matt

Unless the surveyor has a lot of experience with testing Unibond hulls with a moisture meter I would not place a lot of trust in his conclusions. I would visually examine the through-hull drains for evidence of water leaking from them. It is unlikely much water can get into the hull around gunwale mounted hardware although a visual inspection would be worthwhile.

It is good practice to use a cover to protect trailered boats not stored under a shelter. A 150 would be a good candidate for storage in the garage.