Through-Hull Replacement Without Hauling
A failing through-hull or seacock is a problem you absolutely cannot ignore. Hauling out isn't always immediately possible — you might be in a remote anchorage, the yard might be booked, or you might just want to avoid the expense. In some cases, in-water replacement is feasible. In others, it's hauling out now or watching the boat sink later.
When in-water replacement works
- Small through-hulls (1" or less) where a diver can hold a soft patch externally
- Calm conditions, no wave action
- You have a competent diver and a complete spare fitting
- The fitting is accessible from inside the boat without major disassembly
- You have proper backup plans (diver standing by, bilge pumps verified)
The technique (small through-hulls)
- Identify failure mode. If the seacock won't close, you'll work against active flow.
- Brief the diver. Have them confirm hole size and condition externally.
- Prepare the spare fitting, sealant, and inside backup.
- Diver applies soft patch externally (rubber sheet with weight bag).
- From inside, remove the old fitting. Water flow should be limited by the patch.
- Clean and prep the hole, apply sealant.
- Install new fitting. Tighten while diver maintains external patch.
- Diver removes patch; verify seal.
When to haul instead
- Large through-hulls (engine raw water intake, head intake of significant size)
- Failed through-hulls below significant waterline pressure
- Hull damage around the fitting (laminate failure)
- No competent diver available
- Rough conditions
- The fitting requires extensive disassembly to access from inside
Emergency response
If a through-hull or hose fails catastrophically: soft wooden bung hammered into the hole from inside. Every cruising boat should have through-hull-sized wooden bungs in an accessible location. They're a one-time emergency, but they buy hours to organise proper repair.
Frequently asked questions
When in-water works?
Small fittings, calm conditions, competent diver, complete spares.
What size?
Generally 1" or less. Larger fittings need haul-out.
Tools and supplies?
Replacement fitting, sealant, wrenches, wooden bungs as backup.
Diver needed?
Yes — external patch during the swap is essential.
How long does it take?
30 minutes to 2 hours depending on access.