Failed Bilge Pumps Don't Sink Boats
A heavy rainstorm has the potential to sink boats, but it doesn't have to be that way.
With rain predicted all week, it’s a good time to revisit the reality of your boat and rainstorms.
I often hear that either the boat sank because the bilge pump failed or simply that the rainwater could not drain out of the boat fast enough, or it was draining into the bilge — or a combination of the two.
Boats do not sink because bilge pumps fail. They sink because we fail to keep the water on the outside of the boat. So let's not blame this on the bilge pumps. Bilge pumps are designed to remove nuisance water and minor leaks. They provide a short-term solution, not long-term maintenance relief.
So why do boats sink when it rains? Let's look at some very common problems first, and then get into how boat owners can stop worrying when it begins raining.
The most common problem is simply hatch openings in decks that are not dogged down and are not fitted with proper gaskets to make them watertight. Many of these hatches (mostly plastic) are fitted right in front of the outboard well to facilitate access to the outboard mounting bolts, pumps, and hoses. Water backs up in the scuppers and drains directly into the bilge. The pump works and works, but eventually the battery to which it is connected becomes discharged, and down she goes.
Float ball scupper These float-ball style scuppers often are installed when water backflows into the boat. They're not designed to keep a boat afloat.
Next is simply poor design in scupper or freeing port location. The American Boat & Yacht Council (ABYC) has recommended standards for the placement of scuppers, scupper sizes, and the minimum heights above the load waterline of scuppers both while the boat is static and at maximum heel. Time and time again, we see scuppers that are right at the waterline and often well below the waterline due to poor design, though sometimes this happens when boat owners put too much stuff in the stern. An immediate sign of a pending problem is a boat with float-ball-style scuppers to prevent back-flooding; if you're considering such a boat to buy, don't walk away from it — run. Cockpit decks are supposed to be designed to be a minimum of four inches above the waterline but aren't always. Even when a slight amount of water drains into the bilge, the result is disaster because the boats may be designed on the edge with little safety margin. Throw in an anchor and some chain back there, and there's no margin when that big rainstorm hits.
For more information, check out an article by Daniel Rutherford in Seaworthy magazine for US Boat