Moisture spot in transom, 420 db.

Discussion in 'General Maintenance/Repair Questions' started by craigswardmtb, Sep 13, 2019 at 9:46 PM.

  1. craigswardmtb

    craigswardmtb Member

    82
    Jul 2, 2013
    Mystic, CT
    2005 360 Fiesta Vee
    Merc 496's, 8.1L, w/ bravo 3 drives
    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.
     
  2. Golfman25

    Golfman25 Well-Known Member

    608
    Sep 12, 2009
    IL
    281
    V8
    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.
     
  3. craigswardmtb

    craigswardmtb Member

    82
    Jul 2, 2013
    Mystic, CT
    2005 360 Fiesta Vee
    Merc 496's, 8.1L, w/ bravo 3 drives
    Not sure on the readings. I'm awaiting the report. Thx
     
  4. bahamabreisus

    bahamabreisus Well-Known Member

    Oct 25, 2007
    Hampstead NC
    500 dancer, previous 420,390,300 dancers
    detriot 8v92
    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.
     
  5. Golfman25

    Golfman25 Well-Known Member

    608
    Sep 12, 2009
    IL
    281
    V8
    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.
     
  6. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    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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