Proper Sailboat Exhaust Installation

Finding yourself in a sailboat that's becalmed in the fabled Middle of Nowhere is not a fun experience. Your choices are few -- wait for the wind or put on a pair of swim fins, hang your feet over the stern and kick your feet for all you're worth. The third choice requires some planning: you install an engine and turn your "pure" sailboat into an "auxiliary sailing vessel." Once you've installed the engine, you have to install an exhaust system. The system includes a water-lock silencer, a chamber not unlike that of a water pipe, that prevents water from entering the boat.

Things You'll Need

  • Through-hull exhaust hose fitting calipers
  • Hole saw
  • Drill
  • 6-ounce fiberglass cloth
  • Epoxy resin
  • Adhesive marine caulk
  • 1/8-inch drill bit
  • Razor knife
  • Plastic scraper
  • Water-lock silencer
  • Phillips screwdriver
  • First-stage exhaust hose
  • Thread locker
  • Second-stage exhaust hose
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Instructions

    • 1

      Measure the diameter of the through-hull exhaust hose outlet, using calipers. Locate a place on the stern -- the back of the boat -- that doesn't go beneath the water when the boat rolls. This can be on the transom or even on deck. Drill a hole at that location, using a hole saw and a drill. This will expose the core of the boat, so fill in the edges of the hole with at least four layers of 6-ounce fiberglass cloth, with epoxy resin between each layer. Finish the patch over the boat's core with the epoxy. Allow the epoxy to cure for seven days.

    • 2

      Apply adhesive marine caulk to the area on the outside of the hull where the outlet will fit through the hole. Push the exhaust outlet into the new hole and mark the mounting hole with a pencil. Drill 1/8-inch pilot holes in the fiberglass for the outlet's mounting screws. Thread the mounting screws into the pilot holes and tighten with a screwdriver. Tighten the screws only enough to compress a small amount of the caulk from beneath the outlet. Allow the caulk to cure for seven days. Tighten the outlet's mounting screws snugly and trim away any caulk around the outlet, using a razor knife and plastic scraper.

    • 3

      Mount a water-lock silencer longitudinally in the boat's bilge, at least 25 inches below the outfall of the exhaust riser. Loosen the hose clamps on the first-stage exhaust hose, using a Phillips screwdriver. Put a dab of thread locker onto the threads of the hose-clamp screws. Push one end of the first-stage hose onto the exhaust riser and tighten the hose clamps securely. Push the other end of the first-stage hose onto the nearest fitting of the water-lock silencer and tighten the hose clamps snugly.

    • 4

      Loosen the hose clamps on the second-stage exhaust hose. Put a dab of thread locker onto the threads of the hose-clamp screws Push one end of the second-stage hose over the fitting on the water-lock silencer. Push the other end of the second-stage hose over the fitting of the exhaust outlet. Tighten the hose clamps snugly.