Understood - but it would be very useful to have guidance on these various repairs *before* I find the leak, so I can go ahead and fix it when I am out there. Thanks to anyone who can share details. Best, Paris.
1. Where and how do I repair the deck lip silicone?
There is no silicone at the deck lip/seam. If you have a void at the seam, you should repair it with epoxy. Flip the boat upside down, dribble epoxy over the seam and let gravity pull it in, or use a shop vac to suck the epoxy into the void.
2. How to I repair leaks around the pylons?
Pull out the old silicone and apply a fresh bead of silicone.
3. How do I re-bed the gudgeons / drain plugs?
Unscrew the gugeons/plugs, scrape off all the old silicone from the hull & hardware. Apply a new bead of silicone to the flange of the part and re-install .
4. If I find cracks in the body of the hulls, and I'm not worried about cosmetics, just function, what is a fast, affordable but durable way to repair cracks?
If you have cracks in your hull that are leaking water into the hull, that is a structrual issue. The crack needs to be repaired properly using fiberglass & resin. There is no quick repair. Doing a second rate job will lead to the crack returning or possible hull failure.
5. The "keels" of the pontoons get worn away a little each year with dragging across sand and pebbles. What is the best way to build them back up? Again, not concerned about cosmetics, just function, and it would be good to be able to do this repair work on the beach . . . so beach-amenable techniques appreciated.
You need to do a "bottom job". There are numerous posts in the forum as well as Hotline articles giving specific details on how to do this. It basically involves laminating fiberglass tape to the bottom of the hull to build the thickness back up. Doing this work on the beach is a bad idea since you run a high risk of contaminating your repair with dirt/sand meaning you probably won't get a good bond and the repair could literally fall off. Best to do this repair at the beginning or end of the season when your boat is off the beach.