5 Tricks To Measure Moisture In Boat Hull


When buying a boat, you need to take all the necessary steps to ensure that you get value for your money. To avoid paying for a boat featuring a saturated hull core or decks, you need to know how to measure moisture in the boat hull.

If you have been waiting for the best time to buy your first boat, there is a chance that you don’t have experience in measuring moisture in the boat hull. In this article, we will be taking you through various tricks you can use to determine the moisture in the boat hull.

Ideal Methods for Measuring Moisture in Boat Hull

1. Moisture Meter

This is the most popular method of measuring the moisture in the boat hull. The moisture meters generally pick up conduction. This means that if any water, metal, or other conducting elements are available, the moisture meter will end up reading something.

Generally, below the waterline, most boats feature an antifouling paint, which contains copper and other metal composite anti-fouling agents. Your moisture meter will pick this up and show a high reading. For this reason, measuring the moisture in the boat hull using a moisture meter below the centerline is never a good idea.

It is worth noting that some top-side and deck paints may also feature metal composites. For this reason, using the moisture meter as a conclusive way of measuring the moisture in the boat hull is not a good idea. A moisture meter is supposed to be combined with the following methods.

2. Visual Inspection

With a visual inspection, you should be able to determine whether the boat may contain any moisture in its hull. Generally, blisters are a clear indication that the boat may have moisture in the hull.

It is worth noting that not all blisters are osmosis blisters. If you haven’t sat on a boat deck chair in the past, meaning that you are new to boats, figuring out which blisters indicate osmosis may be hard for you. Working with someone who has experience in a wide range of boats is a much better idea.

3. Phenolic Hammering


If you have spent your time in a boatyard in the past, you have probably heard the tap, tap, tap… sound. Chances are, you wondered what the surveyor was doing. The majority of new boat buyers expect the surveyor to show up with a moisture meter, test the moisture in the boat hull and then give them the go-ahead to fit the boat with a steering wheel and start their trip. This is not the case.

By tapping the boat hull, the surveyor gets moisture information that is not available to him or her visually. In most instances, the tapping does not cause any damage. It helps determine delamination with the fiberglass layers, including the delamination which results from osmosis (blisters).

When tapping the boat, the surveyor will be looking for voids. Areas featuring the voids are generally distinguished from areas that do not have voids by a higher pitch. Generally, what you will be listening for when tapping the hull is the difference in the sound made.

Tapping can be done using virtually anything. Depending on the material and the component thickness, tapped variances can be determined using a fingernail, the screwdriver butt, the edge of a coin, and the most preferred tool – the hammer.

The hammers used when buying boats from a boat show or a boatyard are generally made of plastic, steel, bronze, or any other ideal hard material. Above the waterline, most surveyors will prefer to use plastic hammers. Metallic hammers, however, offer more discernible reports.

4. Infrared Thermal Imaging

Thermal imaging is a method of determining the amount of moisture in the boat hull by taking advantage of the Infrared light spectrum portion, which is generally invisible to the naked eye. The Infrared (IR), Thermal scanning, or Thermography, allows the inspector to inspect an environment without any visible light or illumination.

Any object above the absolute zero will give off an amount of thermal radiation. Thermal imaging offers an ideal way to observe the temperature anomalies in the boat’s hull. On the hull and the deck, thermal imaging will help indicate anomalies, generally consistent with delamination, voids, and water intrusion.

Before paying for a boat and investing in upgrading it with boat seats and marine subwoofers, you should work with someone who has a thermal certification. Thermal imaging has some science to it. It takes a professional to figure out the difference between actual anomalies that are consistent with water versus the temperature and reflective anomalies.

Just shooting the thermal image is not enough. Every image has to be tuned properly for analysis to be possible.

5. Scrape Sample Areas

A sharp scraper, held at right angles to the blister will help identify blistering. The scraper helps distinguish between genuine osmotic blistering and solvent entrapment.

If you puncture a couple of blisters and find that they are dry or they release a clear fluid, chances are, you do not have any serious blisters. However, if you end up with an acidic vinegar-like fluid, this could indicate that the boat’s hull features a more serious hydrolysis blister type.

When puncturing the blisters, care is necessary. Some of the blisters may feature fluids under tremendous pressure.

If you find that the blister is very large, puncturing it with an ice pick may be impossible. If the blister is too deep in the laminate, you may have to drill a hole for closer inspection.

Globo Surf Overview

If you are planning to buy and name a boat soon, investing in a survey to help you figure out the amount of moisture in the boat hull is a good idea. While investing in a moisture meter is a good idea, you should not depend on the meter to make your decisions.

As mentioned earlier, moisture meters may offer incorrect results. Irrespective of the type of boat you intend to invest in, you should combine various methods of determining the moisture in the boat hull to get ideal results.

More Sail Reviews:


  1. Methods for Determining Moisture in Fiberglass Hulls, Suenosazules.com
Globo Surf
My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!