My porch lights started leaking very soon after we picked up our Oliver. Water was visible on the inside of the lenses and the bulb socket was beginning to rust a bit. I have the old style lights. Problem was in trying to fit a flat based fixture to a curved trailer. Unfortunately, silicone was used to "seal" the gaps. The job was not that well administered, with gaps in the bead and silicone residue smeared about.There is an old adage in the boating world about silicone: "Silicone sticks to nothing, and nothing sticks to silicone" Perhaps it has uses somewhere, but after 35 years of painting and construction, I still don't know where that is. It's a scourge to any finishing shop, and makes repairs much more involved.
First, I removed the fixtures. They are chromed plastic (sigh) and impossible to clean without ruining the finish on them. I tossed them and bought new ones, luckily they are not too expensive. Next I used plastic razor blades and a citrus based adhesive cleaner to remove the bulk of the silicone that was on the gelcoat. It cleaned up well and looked clean but when misted with water the silicone oils which penetrated the pores of the gelcoat made the water bead up. So, more work to do. No sealant will stick to that for very long. I bought a can of Debond at West Marine here. I then bought 1000, 1500, and 2000 grit automotive sandpaper (3M). I was nervous to take sandpaper to my precious Ollie but I needed more to vanquish the silicone demon! I sprayed the Debond on the 1000 grit paper and wet sanded all around where the fixtures were mounted. I could tell instantly that it was working. Wiped the area clean and repeated with the 1500 grit, then the 2000. All silicone completely gone and just the very slightest loss of sheen to the gelcoat. I talked to Jason on the buffing products they use at the shop and he said they use Shurhold Buff Magic Compound. I bought a foam buffing pad here for my random orbit sander (Festool Rotex) and buffed/polished the area. To my relief, it blended in perfectly, and I am particular. With the area clean of contaminants and polished I reinstalled the new fixtures. I decided to use butyl tape for the sealant. I felt pretty confident that for this situation, it was the best material. But not all butyl tapes are created equal, by a wide margin. The product that kept coming up on all the boating forums was Bed-it Butyl Tape
I can confirm that this is the best stuff I have ever used. Before installing the fixture. I had to re-drill the mounting holes that were way undersized, and then slightly countersink those holes. The gelcoat was badly fractured around the original holes, in a few spots, it just flaked off. Countersinking relieves the compression forces of the screw expanding the glass substrate, which would otherwise fracture the relatively brittle gelcoat. In a thru-bolt situation where there is no compression, the countersink also creates an extra space around the fastener where the butyl tape will be thicker allowing better expansion/contraction ability and a better weather seal. A very good article for those wanting to get deeper into this subject:https://forums.sailboatowners.com/index.php?threads/bedding-deck-hardware-with-bed-it-butyl-tape.117172/
I doubled up the tape top and bottom of the fixture to allow for the curve of the trailer, and added some extra bits where I thought they would be needed in the corners. I also, rolled up some small bits of tape and stuffed them in the enlarged screw holes. It was a warm summer day so no problem pressing the fixture tight to the trailer shell. Screwed down the fixture and with my plastic razor and a tiny bit of paint thinner, cleaned off the excess. A word of caution, try not to get any solvent on these chromed plastic fixtures, it messes up the finish. Next time I would tape off the fixture before installing it to make cleanup safer. As it was I did get a little discoloration to the chrome but not too bad. Finally a good coat of Collinite Fleet paste wax to the whole trailer and fixtures. What a difference! Also swapped out the clear lenses for the amber ones which I like better.
Fixture with original silicone sealant above. You can see some of the fracturing of the gelcoat. The picture doesn't quite capture the flaking around the holes.
Cleaned, polished, re-drilled and countersunk. Some of the chipping went beyond the countersink...but will be covered.
Tape applied, holes filled with a small coil of tape.
Fixture screwed down. Next time, I'll place the tape more carefully so there isn't so much to have to trim off, and carefully mask the fixture to protect it from solvent during cleanup.
Final pic in next post. Guess I can only do three at a time....