Do a quick study of insurance statistics and you’ll soon discover that a majority of boat sinkings are completely preventable.

Today we’ll take a quick look at some of the top causes of sinkings and talk about prevention. Then we’ll address damage control preparation and strategy. Finally, we’ll go over damage control kits you can either make or buy as well as useful materials, equipment and tools you may wish to keep on board.


According to BoatUS, about 70% of sinkings occur at a mooring or dock, not 20 miles off the coast. 33% of those sinkings were caused by the failure of a small part often below the waterline. Knowing what caused other boats to sink will help you concentrate your efforts and better prevent your boat from becoming a statistic.

The good news for you is that 66% of all sinkings are preventable.

Some of The Top Causes:

  • Brittle engine raw water hoses. Hoses wear and eventually fail allowing water to rapidly enter the boat at a rather alarming rate.
  • Old impellers. When impellers fail, the engine can overheat. If the problem goes unnoticed, hot exhaust gases can melt through hoses and cause flooding.
  • Failure of fittings below water lines. Metal fittings corrode and plastic ones can also fail.
  • Forgetting the drain plug. Yes, this happens all too often.
  • Failure of bilge pump. This can be due to a clog, using too low of a pump rating for the situation or a simple lack of power. Lack of power may be caused by: dead batteries, a float switch stuck in the on position, incorrect wiring, corrosion or the power to the pump being turned off.
  • Reverse siphoning. Bilge systems and shower sump pumps generally require a 12-18” riser clearance for proper operation. Failure to maintain this clearance can lead to a reverse siphoning effect which floods the boat.
  • Wear and tear of sterndrive bellows. Marine growth and general wear and tear make sterndrive bellows susceptible to cracking. The structural failure usually starts in the folds.
  • Leaky stuffing box(s). From a few drips to a leaky faucet, neglecting to tighten down or replace stuffing when needed has led to many boats slowly flooding.
  • Tidal changes coupled with poor line management. Lines must be tied in such manner that the boat is able to move up and down in the slip with the tides.


Prevent boat from sinking

Preventive Maintenance – as simple as that may sound, it keeps coming up in many boating topics because of its importance. Create a checklist that covers all seaworthiness and safety issues. Include items of concern such as the top causes of sinkings (as mentioned above), and inspect those items often. 

Damage Control (DC) (Preparation, Assessment, Control)


  • Look and think of all the ways water can get in
  • Plan how to react in each scenario
  • Put together a (DC) kit appropriate for the size of your boat
  • Stow your DC kit in an easily accessible location and inform your crew of its location


Leaking vs. flooding: If pumping efforts cannot keep up, it’s flooding. If your pumping efforts can keep up, its leaking.

Trace source of leaking or flooding: Can you locate the source? If so, can you control (stop) it? Do you have the equipment and materials to do so? Is it safe to do so?

Worst case scenario:  Prepare all hands for the possibility of abandoning ship by donning life jackets and hailing the Coast Guard for assistance.


Once a leak or flooding has been found, if underway (unless you are very close to shore), shut down generators and engines if they present a hazard to work around. Slow or stop the water flow by stuffing anything into the hole as a temporary measure. Break out your damage control kit and apply a more permanent fix.

Damage Control Equipment, Materials and Tools


SeaKits Damage Control Kit

SeaKits Damage Control Kit

Below is a list of some off-the-shelf items that you can start adding to your DC kit. Most are available at marine supply stores and big box home improvement stores.


  • Wedges
  • Gasket Material
  • Rubber Sheets
  • Wire Ties
  • Oakum
  • Hose clamps
  • Underwater Epoxy Patch Kit
  • Duct Tape


Depending on the size of your boat, damage control tools can include:

  • Channel lock pliers
  • Crescent wrench
  • C-clamps
  • Hammer
  • Knife
  • Mallet
  • Pipe wrench
  • Pry bar
  • Saw
  • Screwdrivers
  • Vise grips

Smaller, day cruisers may not have a need for such tools, but it gives you a starting point for what you may need when putting together your own kit.

The Take Aways

Dealing with a sinking vessel is one of the worst situations you can encounter as a boat owner. Armed with the knowledge above and knowing that most sinkings are preventable, your take away here should be to simply spend more time on preventive maintenance, make a routine of inspecting all of the top causes, and put together a DC kit that is appropriate for your size of boat.