Before buying Sarah I knew nothing about caulking. I would just use any old silicon adhesive I could get my hands on at the hardware store. Anyways, after realizing if I don't use the right adhesive I might have to caulk it all over again a year later, I got my act together. That is not something you want to do every 1 or 2 years. This seemingly simple task usually ends up a disaster with caulking all over your hands, in your hair, basically exactly where you don't want it to be.
After some of these messy experiences I quickly learned the more masking the better. cover anything you don't want the goop on or it will be impossible to clean up, requiring a roll of paper towels and a full quart of acetone. During the process you usually end up loosing a glove and before you know it, this nasty stuff is all over your hands.
Following a number of projects I've settled on using 3 types of leak stoppers on Sarah;
1. 3M 4000 uv a lighter duty adhesive that bonds with more materials than 4200 (including plastics). Typically used for Portholes, Hatches, Electrical Fittings; anything with direct sunlight exposure with no large forces
2. 3M 4200 a heavy duty adhesive (but not quite as permanent as 5200 if you ever want to remove it). Used on the Bowsprit, Stanchions, Windvane, Grounding Plate, Chainplates, Anchor Roller; anything that requires structural bonds between wood, metal and gelcoat
3. 3M Premium Silicon Glue a household silicon glue that can handle a wide range of temperatures. Used on heater chimney; stuff that sees high temperatures (Rarely used, I've had the same tube for the last 5 years).
More or less the system has worked. The portholes are watertight, the bowsprit and wind vane are still on the boat… Before I had any clue about what I was doing I used 4200 as a bead to seal the center hatch, turns out it doesn't bond to plastic so after sun exposure and time the hatch started leaking again, time to try 4000 uv and see what happens. Will let you know the results in a year.
Thought I would re-seal the heater chimney at the same time. For this I will use an inner ring of silicon glue and an outer ring of 4000 uv.