Check your sealed decks, boating safety watchdog warns
A number of on-water incidents involving sealed deck boats has Marine Safety Victoria worriedMarine Safety Victoria has issued a warning to boaters after identifying a lack of maintenance on small boats with sealed decks was causing problems for owners.
MSV said it had inspected a number of boats between 4.0 and 7.0 metres in length, which were “supposed to have sealed decks”.
“If you have a small boat with a deck that is intended to be watertight, there are a number of issues to look out for,” the boating safety watchdog said.
Sealed decks usually have watertight compartments built in under the floor to help with maintaining level flotation, which keeps the hull parallel to the water if the boat sinks. These spaces can be filled with foam to help with buoyancy, or are used for underfloor fuel tanks.
These spaces are usually accessed via round “spin-out” inspection hatches, which need to be closed tightly to remain watertight. Anything running through a sealed deck, such as wiring or fuel lines, usually enter the deck up near the bulwarks.
Bilge pumps and scuppers
Similar to other boats, a sealed deck still uses a sump that collects any water that makes its way into the deck. Because the deck sits higher than the water level, these boats are also often fitted with scuppers that allow any water that enters the cockpit to drain out. In most cases, these are fitted with one-way valves that allow water to flow out, but not back into the cockpit.
Most boats are also equipped with a bilge pump that drains the sump. Some boats include a floating switch that will automatically switch on the bilge pump if the bilge fills to a certain level, and even more importantly, a console-mounted alarm to warn that the boat is taking on water.
“Typically an incident occurs where water collects out of sight of a sealed deck that has failed. The consequences are serious, with outcomes including flooding, capsizing and sinking with potential fatalities,” MSV said.
“For the sealed deck to work properly, all of the above are designed to work together to keep a vessel safe. Each item must be maintained in good condition.”
More than one failure
According to MSV, some of the boats it had inspected had suffered more than one failure when they took on water.
It said a timeline of a typical sinking of a sealed deck boat was:
Boattakes on water, due to:
- Boat leaking because of hull structural failure
- Water entering below deck compartments, because of water being taken on deck due to waves, spray, rain and deck structural failure and/or failure of watertight spinouts and/or failure of fuel tank soft patches and/or unsealed deck penetrations for wiring, cables etc.
Crew not being able to remove water, due to:
- Not knowing water was entering vessel, because of no operating bilge pump alarm
- Water not being able to be removed, because of no working pump, or no working float switch to operate pump, or sump or bilge access too small to allow removal of water by bailer or bucket.
Boat capsizes due to:
- Water in hull and on deck, because sufficient water has entered to increase mass of boat for freeboard to be lost, and/or insufficient flotation to support increased mass, and/or water in compartments, tanks and on deck creates sloshing water surfaces which reduce stability
Boat floats in a poor attitude or sinks, due to:
- Amount and position of flotation materials will determine what happens to vessel - check your Australian Builders Plate. Note that a vessel with “level” flotation performs best, by staying as upright as possible.
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