How To Buy A Sport Boat --No. 10: Scuppers - 09/14/2011

Every sportboat has scuppers. But do you know where yours drain – is it overboard or in the bilge? Knowing the answer to that question could mean the difference between being a happy boater or finding your pride-and-joy sunk at its mooring. Check out any boat’s scuppers before buying.

These are the size of scuppers and the design we like to see on all small boats to drain their cockpits. This picture is on a center console. We’d say sportboats with self-draining cockpits need only one on each side.

Scuppers are holes in the cockpit sole of your boat, usually at the stern and the lowest part, which drain water. If there were no scuppers in your cockpit your boat could, if left out in the rain, or seas came aboard, fill with water.

This is typically the kind of cockpit scupper you will find in an American-built sportboat. Note that while the holes will keep debris out of the drain only about 50% of the orifice is actually open to drainage. It would not take much to stop-up this scupper.
Water In the Cockpit?

Small sportboats are made for lakes and rivers and not huge lakes or the ocean. Large sportboats are made for larger bodies of water where a wave might wash aboard, but this does not happen often. Very few sportboat owners take water over the bow or the boat’s sides simply because most sportboat owners are sensible enough not to be out in conditions that are too rough for their vessels to handle.

Generally, the biggest worry owners of sportboats have when it comes to water getting in the cockpit is from rain water. Boats left on a mooring or at the dock which do not have a water-tight cover need to be “self-draining.”
Another scupper plate design which can also be easily clogged by leaves or other stuff. This builder has put in two scupper drains as added insurance that the cockpit will drain.
Self-Draining Cockpit

A self-draining cockpit is one that that drains overboard automatically thanks to gravity and the fact that the drain outlet in the hull is above the waterline. A simple rubber or sunteetic pipe or tube runs from the scupper in the cockpit to the hull side. Usually there are two scuppers, one to port and one to starboard, in the lowest part of the boat, almost always in the stern. There are two because if a boat lists slightly to one side the cockpit will always drain right away.

Boats with single drains, usually on the centerline, will drain nicely if the boats are balanced level. But if the boat lists to one side or the other when at rest then water will have to fill the cockpit until is begins to reach the centerline scupper in order to begin draining.

We like this scupper design better because it maximizes water flow yet the cross bar protects the drain from clogging.

We think a self-draining cockpit is the best system to have because the boat’s design relies on gravity to drain it. As long as the scuppers do not become blocked and their drains stay above the waterline, the cockpit will be able to take a summer monsoon and stay afloat. However, if a boat does not have a “self-draining” cockpit, then the scuppers drain into the boat’s bilge.

The biggest and best cockpit scuppers in small boats are found in the best-made center consoles. Because these boats will be going offshore in all sorts of weather, and sloppy seas can come aboard, they need large, quick-draining scuppers for dewatering. This arrangement is over-kill for most sportboats, but it demonstrates good, robust design.
Draining to the Bilge

Many entry-level and low price-point sportboats have cockpit scuppers which drain into the bilge. These are boats that are designed to be trailered and not be left on a mooring or in a slip overnight. These boats usually have an automatic bilge pump in the lowest part of the boat (often in the stern) and have a float switch or some other device that turns on the bilge pump when water rises above a certain point.

Typically this is what boats look like when they fill with rain water at the dock. In this case a battery may have been exhausted long before the rain stopped.

We do not recommend that you leave boats with cockpits that drain into the bilge on a mooring or even in a slip when it rains. The reason is that a battery will only pump for so long before it runs out of power. Then, your boat’s bilge will fill with water. If left unattended it can sink.

Another bugaboo of this system is the float switch itself which can easily become stuck in the up or down position by debris in the bilge. If the switch is stuck in the up position the pump will run constantly and run down the battery. If it is stuck in the down position the pump will not be activated and your bilge and boat can fill with water.

Each year more boats sink at the dock than any other place.

This is a storage compartment in the deck of a small boat. Note the rubber gasket (A) in the edge of the hatch cover, the deep channel (B) around the parameter of the compartment and the drain in the lowest corner (C) of the channel. With this design chances are that heavy rain may not even get past the rubber gasket, but if it does it will drain off quickly.

Even boats with a conventional canvas cover with cockpits that drain into the bilge are problematical in stormy weather. The reason is that high winds or gusts can get under the canvas and pull off the cover or part of it and allow the cockpit to fill with rainwater.

Some builders have gone to quite a bit of trouble to fashion covers that can resist high winds, so talk to your dealer and get his advice.

Boats 20’ and under built today must have level flotation as seen here. This vessel has no scuppers and this is what happens when unattended during a rain storm.
Plugged Scuppers

Even with a self-draining cockpit, if scuppers or their drain pipes become plugged, it is like having no scuppers at all. That is why some builders have plates with holes in them that are so small that debris cannot get swept down and clog the drain tubes. However, if these scupper plates become covered with leaves blown into the boat, a rag left on a cushion that washes over the scupper, or a canvas that blows over the top of the drain the scupper will not work. It is for this reason that we think there should always be two scuppers in the cockpit of a sportboat.

This is a well-designed storage compartment under a seat. Note the high lip around the hatch (A) and observe that the channel is angled down to drain water into the foot well. There is a drain in this locker liner (B) which probably goes into the bilge.

It is because of Murphy’s Law that we like scuppers that are large, say, 2” (50 cm) and ones that have cross bars in them rather than plates over them, and two of them. In this way small particles and light debris can wash right through, but larger objects that could stop up the drain are kept out by the cross bars. Redundancy in most things is good on a boat.

Draining Deck Storage

Virtually every sportboat has a hatch in the cockpit sole for storage. This compartment is usually the most vulnerable on the boat to water intrusion. Usually skis or wakeboards are intended to be placed there, so while they will not be damaged by the water, getting the water out can be a hassle.

If there is no lip around the hatch with a channel to direct the water to a drain, then the compartment will fill with water during a rain storm. In some sportboats, particularly those with a low price-point, the bottom of this compartment is probably also the bilge. In this case there should be limber holes to drain rain water back to the bilge pump in the stern.

Tying up a boat at a slip does not prevent it from sinking. Our guess is that this boat enduring a violent storm with both wind and waves and has a cockpit that drained into the bilge or scuppers that became unplugged.

More expensive sportboats will typically have a liner in the sole locker, or even a lift-out fiberglass pan. In either case, these containers may or may not have a drain hole that leads to the bilge.

This is an anchor locker on a small boat. We like the double ports to allow two lines to come out when the hatch is closed, but this compartment will collect lots of water. In this case the best solution would be to drill a hole through the hull above the waterline and let the water drain overboard, rather than into the bilge. This is the solution often used on large boats and it can work just as well on sportboats, however we rarely see it done.

Likewise, in most sportboats water from the anchor locker, and water that gets into under-seat storage, will find its way into the bilge unless there are internal liners that do not drain. In that case if water gets into them you will have water in the bottom of your storage bin.

Have Two Batteries

If you have any drains that go into the bilge we recommend that you have two batteries. One battery is the “House” battery. It is from this battery that power is drawn upon for the bilge pumps and lights. The other battery will be used exclusively for starting the engine. The engine’s alternator or magneto will charge both batteries.