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david (david)
Posted on Wednesday, October 29, 2003 - 10:26 am:   Edit Post Print Post

Cockpit "drainage holes" are called "scuppers." The scuppers drain through hoses and through-hulls to the ocean. Your cockpit is almost certainly above the waterline. Gravity does the rest.

It is useful to inspect the hoses and thru-hulls occasionally. If the hoses fail or a thru-hull breaks, the boat will start to sink. Its not good to put off knowing where the thru-hulls are until the boat is taking on water. By that time they may be underwater and much more difficult to locate.

Keeping the hoses in good shape and making sure the valves on the thru-hulls work can prevent surprises. Occasionally the valves may need lubrication, although just moving them periodically helps keep them free.

Carrying a set of tapered wooden plugs that span the size range of through-hulls and the holes they are mounted in is a very good idea and cheap insurance. Keep the plugs dry. If you have to press one into a hole, the wood will swell and tend to keep it there. Make sure the plugs are not buried under a ton of stuff. Don't forget where they are.

Keeping a plug tied to each through-hull is not necessarily a good idea. The thinking here is that you have the right size plug where you need it. However, a leak may not occur the way you anticipate. If the entire thru-hull comes out (could happen), the plug you have selected may be the wrong size. Or the plug may not fit far enough into the hole to seal. There could be a strainer on the outside, the opening could be narrowed-down with calcified marine deposits, or the end of the plug could hit some valve component. Or the plugs may get wet before you need them.


Water in the bilge (below the waterline) usually must be pumped out manually or with an electric pump.

Some powerboats have "self drainers" that are actually below the waterline when the boat is at rest. These devices have one-way valves to keep water from entering the boat. At speed, an area of low pressure is created in the water at the boat's stern. The drainers open and any water in the hull flows out.

Posted on Thursday, October 23, 2003 - 04:50 pm:   Edit Post Print Post

My boat has two drainage holes in the forward part of the cockpit. I assume that the holes are connected to hoses and thru-hulls but I don't understand the physics involved. Can someone explain how this set-up works? There is never any water inside the boat (it's always "dry as a bone") so the water is getting to the ocean and I would like to know how. I have a Columbia 22.

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