Fasteners thru hull of thin hull fiberglass boat below waterline

[Horned Toad]

Looking for best way to repair previous owners work. Boat is a 2012 Livingston 12ft. Fish finder gimbal mount was installed to center of boat with 1" #8 sheet metal screws that broke thru bottom of hull and cracked out the gelcoat quite a bit. The end of the fastener and surrounding area was coated with some version of silicone. I think this is a source of water intrusion into the voids in the Livingston. I want to remount the Fishfinder in aprox. the same spot, but want to ensure the thru hull holes are repaired properly and the new fasteners are done correctly. Thinking of drilling out current holes slightly and placing SS machine screws with SS screw cups filled and coated with silicone from bottom up. Or, should I fill holes with epoxy and set bolts in epoxy? The hull of theses boats flex quite a bit. Thanks.

 

[alldodge]

Need to get to dry wood, without getting to dry wood you'll only be doing a repair again later.

Should have been drilled larger hole, fill with epoxy then drill for smaller screw. That or epoxy a piece of plastic/Starboard or other and use it to mount

 

[Horned Toad]

Need to get to dry wood, without getting to dry wood you'll only be doing a repair again later.

Should have been drilled larger hole, fill with epoxy then drill for smaller screw. That or epoxy a piece of plastic/Starboard or other and use it to mount

No wood, unless as core sealed between fiberglass sheets.

Can I just epoxy plastic/starboard on to inside of boat and expect it to stay put without adding any type of glass cloth over it?

 

[flashback]

Chamfer the hole a bit inside and out, fill with epoxy filler and fair when dry. Then scuff up the inside a bit and epoxy your mounting block.

 

[Lowlysubaruguy]

Heres the thing about plugging fiberglass. It’s a 50/50 fix. It really need the Surfaces ground out and tapered a 1/8 hole will be a three inch repair when it’s done on both sides. While yes you can drill it and pack it with fiberglass or epoxy it’s a plug not a repair. Myself if it was a few small screw holes I’d coat the hole and the threads on new screws with marine 5200 and just patch that thing with screws. It’s a Livingston the hull should be fairly thick. 5200 is pretty solid fix for threaded fasteners that you dont plan on removing ever.

 

[sendywilliamson]

Hello, I am new here but not new in this but I just want to say that It's important to repair the previous owner's work to prevent any further water intrusion and damage to the boat. Here are some steps you can follow:

1. Start by removing the broken screws and any remaining silicone around the holes.
2. Clean the area thoroughly with acetone or a marine cleaner to remove any residue.
3. Use a drill to enlarge the holes slightly, making sure to remove any damaged fiberglass or gelcoat.
4. Fill the holes with a marine-grade epoxy filler and allow it to cure according to the manufacturer's instructions.
5. Once the epoxy is cured, drill new pilot holes for the screws in the center of the filled holes.
6. Use stainless steel machine screws and screw cups to secure the fish finder in place, making sure to apply a marine sealant or silicone around the screws and screw cups before tightening.
7. Finally, inspect the repair periodically and reapply sealant as needed to ensure no water intrusion. MIbridges

It's important to note that drilling new holes near the repaired area may cause additional stress to the hull, so it's best to try to use the existing holes if possible. If you do need to drill new holes, make sure they are far enough away from the repaired area to avoid any further damage.

 

[dingbat]

Repairing holes or stripped threads is easy using the procedure outlined below. Have repaired deck screws, fish finder mount holes in transoms, etc.

Drill the hole a bit over sized and through the material. Counter sink the gel coat side a bit to make it easier to fill the void.

Clean debris from the hole. Apply a little penetrating oil or a silicone spray (like WD-40) to the new fasteners to act as a release agent; wipe off excess film.

Mix Marine-Tex and fill the countersink then fill the hole from the inside 3/4 of the hull thickness deep.

Apply a small amount of Marine Tex to the fastener, being sure to fill in around the threads. With a slight twisting motion, insert the fastener in to the hole and allow the epoxy to cure for the full 24 hours. Marine-Tex will have the threads cast into it, and the fastener can be backed out if necessary.

A wrench or a screwdriver with a little extra elbow grease may be needed the very first time the re-inserted fastener is removed since it will stick the first time it is backed out.

 

[KJM]

If the problem is the sharp ends of the screws protruding thtu to the outside of the hull and leaking, but the screws themselves are still solid, I would just use a grinder to flatten off the screw tips and go a LITTLE deeper into the hull. Then fill the void on the outside with epoxy or make a little peanut butter, sand off smooth and either paint or gelcoat. Just dont grind thru the hull!

 

[airshot]

Never use silicone on a boat, especially below the water line !! There are good marine sealants that will do the job. Silicone is never more than a tempory fix and it will fail !!

 

[Grub54891]

For a cored hull you need to drill a larger hole than the transducer from the inside but not through the outside. Add casting epoxy and hen proceed with the install. Here's a link on how to do them.

Installing a Thru-Hull Transducer | West Marine

West Marine is committed to outfitting your life on the water. With over 250 store locations, 100,000 products in stock, and knowledgeable Associates, trust West Marine for your boating, sailing, fishing, or paddling needs. Shop with confidence - get free shipping to home or stores + price match...

www.westmarine.com