Partner Sites:  www.BOEmarine.com | www.CBangler.com | www.BandofBoaters.com

  • Rotten Boat Coring, A Successful Repair

    From time to time there are comments on CSR about coring. Many people consider cored hull boats to be evil and won’t even consider owning one. The truth of the matter is that cored construction is quite common and is used on many high line and expensive brands.
    If you have read many threads on boat buying, you almost always see the recommendation to survey prospective boats and have that survey done by a competent marine surveyor. I was the Sea Ray dealer (where we also happen to keep our boat) the last couple of weeks, and saw the first cored hull problem this dealer has had to deal with. I thought some of you might like to see the problem and how the dealer and Sea Ray handled it.


    The boat involved is a 2000 460DA. The owner noticed the boat listing in the slip. At first, several months ago, it was a little bit, barely noticeable from the stern. Then it got worse. Eventually the generator exhaust was almost submerged which on this boat means she was listing about 3” to the port side. The dealer found the port side hull vent had been leaking. The vent hole is sawed into the cored side, so any leak can let water get into the cored area between the inner skin and the outer gelcoated skin. This particular boat had been leaking a while, and the hull side coring was found to be wet from the stern to about 5’ forward of the hull vent…….a total of about 10’ worth of wet hull/coring. The fiberglass guy at the marina identified the wet area by sounding the hull and with a moisture meter.


    This is a photo of the water draining out of the core:



    The hull vents were removed from the hull and about 3/16” holes were drilled in the bottom of the cored area to allow it to drain naturally. The bow was raised slightly until no more water would gravity drain out of the lowest, aft-most hole.


    Next, shop vacs were taped to the hull and any remaining water was vacuumed out of the cored side.


    Even though a large area of the core got wet, the extent of the damage in this case was some rotten coring between the inner and outer skins around the hole sawed in the hull for the vent. The damaged area needing repair was limited to the area on the bottom and aft end of the vent which was about 1” to1-1/4” into the core from the opening. The rotten area was dug out and removed, as shown here:





    The repair was done by digging out the rotten balsa and filling the area between the skins with West Systems Epoxy thickened with #403 Microfibers. The holes drilled in the hull were filled and sanded smooth. Since the repaired area at the vent was covered by the vent panel itself and the holes drilled in the hull were below the waterline and in an area covered with bottom paint, gelcoat repairs were not necessary.


    While the usual feeling here on CSR is that wet coring is the kiss of death, this is a case where a bad situation was caught and properly repaired with no long term negative impact on the boat or its value. Since the rotten balsa was limited to a relatively small area, and the wet area was easily drained and dried out, the boat was only out of service about 10 days and the cost of the repair was very low. In fact, the owner wanted the boot stripe replaced while the boat was out of the water and it took longer to get the stripe from Sea Ray than it did to fix the wet coring.


    If you have read much of what I post about establishing and maintaining positive dealer relationships, here is a good example of why: This boat is kept at the dealer’s marina, it is well maintained and most of the maintenance is done by the dealership, so the dealer knows the boat’s history. The Service Manager was able to get Sea Ray to handle the repairs for the owner and an accommodation even though the hull is a 2000 model…….4 years out of the hull warranty.


    Summary:


    • A wet core isn’t a good thing, but does not necessarily mean the boat is DOA.


    • A wet core can be repaired reasonable quickly and easily without breaking the bank. This example was less than $2000.


    • A core with significant wood rot is a different story since the rotten core must be removed and replaced.


    • Any part or item mounted in a sawn in hole in a cored structure is a potential source of water intrusion into the coring. Consider having any such items like hull side vents, windlass foot switches, spotlights, etc. removed and the coring sealed with epoxy or resin then re-bed and remount the removed part.


    • The cause of the problem pictured here was not the fact that the manufacturer chose to use cored construction; the coring was properly done and without defect. In this case, there was a bad seal around the side vent.


    • Were this a boat being purchased without a survey or the wet area not found by a surveyor, the entire cored side could have rotted which would have made the term “major repair” an understatement.


    • A wet core doesn’t usually just happen with no notice. An observant owner who knows his boat will usually see signs that something isn’t right… Look for listing, unexplained sluggishness or bad performance, staining, mold/mildew, drips, leaks, water/moisture where there should not be any.
    Comments 10 Comments
    1. abog87's Avatar
      abog87 -
      Gary, Chicago. 84 Sundancer 260. very timely article. I just purchase this, my first boat, last fall. I am having a heavy duty dive ladder fabricated (with quick release mounts) to be set up on top of the platform. My survey showed slight moisture on a small area around one bolt on the platform. My fabricator is making a stainless steel plate to run the length of the platform on the underside on the outer edge. Then there will be new struts from the stern to the plate. The fabricator is not a marine specialist so I would like some advice to pass on to them on how to attach the struts to the hull and the platform to the plate. Thanks Great site.
    1. MonacoMike's Avatar
      MonacoMike -
      Deleted
    1. albuild's Avatar
      albuild -
      why cant you drill holes on the inside of the boat to allow the water to drain into the engine compartmant making repair easyier any one know ?
    1. fwebster's Avatar
      fwebster -
      Because the bottom of the core can be lower that the floor in the engine room. You cannot get to it from the inside without removing the floor of the bilge, which would be a lot more work than fixing a few 3/16"-1/4" holes below the waterline where no gelcoat work is needed.
    1. albuild's Avatar
      albuild -
      Quote Originally Posted by fwebster View Post
      Because the bottom of the core can be lower that the floor in the engine room. You cannot get to it from the inside without removing the floor of the bilge, which would be a lot more work than fixing a few 3/16"-1/4" holes below the waterline where no gelcoat work is needed.
      thanks for the reply i will drill holes in the spring to see if there is water in the core then try to find out where it got in do you think if i drilled one hole then used low pressure compressed air into the hole it would help me find where the water got in any ideas would be really great thanks everybody
    1. boater seabuddy's Avatar
      boater seabuddy -
      Any part or item mounted in a sawn in hole in a cored structure is a potential source of water intrusion into the coring. Consider having any such items like hull side vents, windlass foot switches, spotlights, etc. removed and the coring sealed with epoxy or resin then re-bed and remount the removed part. Sea Ray fixed this boat. Good.
    1. boater seabuddy's Avatar
      boater seabuddy -
      I am not so sure that all boat builders would agree with "the coring was properly done" in a cored area around the vent.
    1. Linesix's Avatar
      Linesix -
      In my professional opinion, gelcoat should ALWAYS be applied to any repair below the waterline regardless to weather you see it or not. Gelcoat is the only material on the boat that is 100% waterproof. Also, what happens the next winter the boat is hauled and blocked? That remaining wet core will freeze, expand, causing further damage.
    1. fwebster's Avatar
      fwebster -
      The boat in the photos contained in the article was repaired 3-1/2 years/3 winters ago, was sold last year due to the owner's failing health and passed a rigorous survey by a SAMS/NAMS certified surveyor that showed no moisture in the structure anywhere.
    1. Lazy Daze's Avatar
      Lazy Daze -
      Quote Originally Posted by Linesix View Post
      In my professional opinion, gelcoat should ALWAYS be applied to any repair below the waterline regardless to weather you see it or not. Gelcoat is the only material on the boat that is 100% waterproof. Also, what happens the next winter the boat is hauled and blocked? That remaining wet core will freeze, expand, causing further damage.
      Actually, gelcoat is not 100% waterproof. Newer gelcoats are much better, but still not 100%. Epoxy is MORE waterproof than gelcoat. I've done under-the-waterline repairs on numerous boats over the years using epoxy and, unless cosmetics come into play, have never re-gelcoated. No issues.