Why sailboats sink and five tips to prevent it

by Scott Croft, BoatU.S. on 8 Dec 2007 A study of 100 sailboat sinkings from the BoatU.S. Insurance claims files could help prevent your sailboat from becoming a statistic. 'The sinkings were found to be divided evenly into two broad categories – those that sank at the dock and those that sank while underway,' said BoatU.S. Marine Insurance Technical Director Bob Adriance.

'However, when it came to sinking underway, a sailboat’s deep draft became the obvious factor,' Adriance continued. Striking a submerged object was found to cause 40% of the sinkings while underway. Next on the underway list was a broken prop shaft or strut (16%) and damaged or deteriorated fittings below the waterline (16%). 'Prop shaft corrosion seems to be a bigger issue with sailboats than with powerboats as auxiliary sailboat engines are not run as often, allowing corrosion to set in,' added Adriance.

The most common cause of dockside sinkings were found to be the result of deteriorated or damaged or corroded fittings such as intakes, seacocks, and drains below the waterline. Stuffing box leaks were number two on the dockside list.

The complete study results are as follows:

Sinking at the Dock
Below waterline fitting 44%
Stuffing box leak 33%
Keel and centerboard 7%
Rain 7%
Head back-siphoning 3%
Above waterline fitting 3%
City Water hookup 3%

Sinking Underway
Struck submerged object 40%
Prop shaft or strut 16%
Below waterline fitting 16%
Grounding 8%
Stuffing box leak 8%
Storm/knockdowns 8%
Above waterline fitting 4%


Five Tips for Prevent a Sailboat Sinking:

- Any time your boat hits bottom, immediately inspect the bilge and keel bolts or centerboard pennant and hinge. To be safe, inspect again an hour later.

- Routinely — twice a season — inspect all below the waterline fittings, hoses, and hardware. If the fitting is long enough, its good practice to have two marine-rated stainless steel clamps on all hose ends. Any hoses showing signs of rot should be immediately replaced.

- When at rest, stuffing boxes should never leak. If leaking persists after the packing gland nut has been tightened, the packing must be replaced.

- Don’t ignore through-hull fittings or hoses that are installed above the waterline. While they may appear to be 'safely' above the water level, they can leak when heeled over in a seaway, or when snow or ice forces the boat under.

- A winter haul out is the perfect time to inspect the prop shaft and cutless bearing.