How do I repair screw holes in the bottom of my fiberglass boat?

Take the boat out of the water. Remove the screws. Totally remove them. Never ever screw anything to the bottom of a hull. Never. You now have six holes in the bottom of your boat. Make sure they are clean and dry. Epoxy can the thickened with a special filler so it's the consistency of peanut butter. Go to a marine store and buy the epoxy and filler. Epoxy will not stick to brown packing tape. Buy a roll of 2 inch wide brown packing tape, not clear packing tape, brown packing tape. Mix the epoxy resin, hardener and filler according to the directions. When you have it the consistency of peanut butter, you're ready for the next step. Cut a two inch piece of packing tape. Place it on a flat surface with the sticky side up. Put a blob of the thickened epoxy on the sticky side of the tape. Be generous. Pick up the tape and apply it over the hole, pushing the epoxy into the hole and sealing the tape onto the hull. It will keep the epoxy from sagging out of the holes. Remove any epoxy that ...  more

This is a job for Marine-Tex. It's a 2-part fiberglass putty made for this sort of thing. Bonds with the hull. Thick enough to stay where you put it so you don't have to invert the boat. My keel is almost completely covered in marine-tex, from being scraped on boat ramps, gravel lake bottoms, the trailer, etc. Also a few small holes from rocks that penetrated all the way through the inner hull, from when I inadvertently beached her (I mean "really" beached her) one night. :-) All repairs done while lying on my back with the boat on the trailer. This stuff right here: <a href="http://www.marinetex.com/marinetexepoxyputty.html" rel="nofollow">http://www.marinetex.com/marinetexepoxyp…</a> Cut the screws off with a dremel, grind 'em flush with the hull, and drill 'em to depth of about 1/2", maybe a bit more. Clean the area thoroghly and wipe it down with a solvent (paint thinner will do) to remove all the dust. Mix up a batch of marine-tex and fill the holes, when it cures, sand it down ...  more

Well what is going to fall off if you cut these screws off? It will be painful I fear. I have a funny story about a similar situation. I saw a lovely fibreglass 17 foot half cab in quite good condition at an auction once. We all looked her over talking to the owner and it looked a certain sale - until I found half a dozen screws sticking out the bottom underneath each side!! You could not take the boat off the trailer due to them as one at least went into the bunks, screwing the boat to the trailer. It turned out this chap had whacked two new seats in that morning, and not thought a thing about using 4" screws. Well he hadn't thought about anything as far as I was concerned. Ten years later that bloke still hates my guts for "costing him a good sale price" at that auction. (It was passed in with no bid) He trimmed them off with a grinder and touched up with a bit of gel coat. He sold the boat to an old school friend of mine and the new owner eventually spent over $1500 getting it ...  more