Moisture spot in transom, 420 db.

craigswardmtb

Active Member
SILVER Sponsor
Jul 2, 2013
315
Mystic, CT
Boat Info
2004 420 DB
2005 360 Fiesta Vee
Engines
Cummins 6CTA
We surveyed a 420 DB today. The survey revealed a small moisture spot on the transom above the stbd trim tab but still below the water line. The moisture meter revealed a semi high reading but the percussive testing was perfect on this spot and the rest of the boat.
The boat was out of the water for 24 hours, and the reading was through the bottom paint. Also my understanding is that this is a solid fiberglass boat below waterline.
The surveyor did not seem too concerned of the high reading. But did say it is something you should be aware of. I would appreciate any insights you guys might have.
 
My surveyor told me bottom paint can mess with moisture readings. How where the readings relative to the spot?

I would confirm the transom material. As long as it's not cored, you're probably good. Something to keep an eye on. Could remove the trim tab over the winter and see if any water comes out of the holes.
 
I trust the old fashion hammer test long before I would a moisture meter. I was on a survey once on a 480DB, moisture meter pegged, we walked. The seller actually had a core sample pulled after we walked, no moisture found in the sample. This was according to the sellers broker, so the grain of salt should be taken, but interesting.
 
The meter is definitely more art than science. I my case, we saw the moisture meter peg, and then got the hammer out. Half the platform structure was hollowed out. You could hear the change. In the OPs non-cored case there would be nowhere for the moisture to go. So much less of an issue.
 
Actually, there is a place or 2 for moisture to go............larger Sea Rays have a piece of marine plywood in the transom layup, usually above the waterline. The hull is considered a solid hull because the plywood is only there to mount things like trim pump, plumbing, wiring, etc on. The other place moisture can collect is in a void in the transom. Below the waterline, the void can continue to grow. The fix is easy but kind of ugly because you just have to go to grinding until you find the edge of the void and dry fiberglass.

On my first bottom job on my old 390EC< the yard guy was new and he overtightened the big hull zinc in the center of the transom and cracked the gelcoat. The bolt was only 3/8" in diameter, but wee had to grind out 12" X 18" spot the next year when we hauled out to check the bottom.....and this is why I haul out to check the bottom every year I don't paint the bottom.
 

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