Caulking

Athough I have used sikaflex 291 on past projects, I think I will try Boatlife's Life Caulk. If you're doing a big job, like all of your fittings within a season, then the caulk tubes for caulking gun is probably worth it, but I find that when doing reasonable size jobs, the little tube is sufficient. Good Caulks have a shelf life of about a year. I usually end up throwing the expensive stuff out. If Sika made smaller tubes, I would definitely stick with them as I have been really pleased with the product. I think the key though is proper preparation and technique. For example, not squeezing the caulk out when tightening is probably the single most important thing in ensuring a watertight seal. I usually tighten the bolts snug and wait 24 hours before final tightening. When it's time to fully tighten, I keep the head of the bolt stationary, I tighten using the nut. The caulk is flexible but not fully cured (3-7 days for full curing)and therefore creates a flexible watertight gasket that should last a long time. I also make sure to coat the edges of all holes thoroughly as well as under the bolt heads. When you're done, you can use an exacto knife to trim any
excess....the hardest part is getting all old bedding of the bolts and from the holes!
Hope this helps. I'm sure others have effective ways to  do this job as well......