There are two things I’d planned to write about this winter: the Wahoo!’s above deck drain system and the Wahoo!’s below deck drain system. Both are among the quirkiest aspects of these boats and among most commented on/asked about. They sure had me stumped when I first bought my Wahoo! It’s the third week in February all of a sudden and Spring is just around the corner. So time to get writing before the boating and fishing season take over.

This post will be about the Wahoo!’s above-deck drain system. Specifically it will be about the self-bailing deck drain system employed by most smaller Wahoo!s, whereby water from the deck is designed to exit out of a scupper in the stern. I may not get all the facts complete or correct the first time. So if you are are a Wahoo! owner past or present and have corrections or additional info, please add a comment or send an email. I’ll continue to update this article as necessary.

The self-bailing design concept

Smaller Wahoo!s have a deck draining system that is designed to be self-bailing. The idea is that, when underway, any water that accumulates on the deck, be it from rain, spray, waves over the gunnels, or whatever, is designed to run to the rear of the boat and collect in a small sump basin located just inside the stern. A scupper connects the basin to the outside of the boat. Gravity from the boat’s forward motion forces water from the sump basin through the scupper and out of the boat. (Note that it is only the Wahoo!’s deck only that is designed to be self-bailing, not the hull interior (that is, the bilge).)

Theoretically, the benefits of this self-bailing design include:

  • No need for bilge pumps (which can fail). The system takes care of itself.
  • The boat’s bilge does not take on water because the self-bailing deck drain precludes water ever getting down there.
  • When the boat is at rest, some water comes in through the sump basin scupper. But this water levels out and never goes above the top of the basin.

 

The components

These are the components of the system (that is, the related parts designed to make it work), listed from front to back:

  • Forward compartment drains: Wahoo!s, depending on the model, have several above-deck compartments. An anchor storage compartment in the bow is common to many models. Some also have a combination cooler/seat positioned just forward of the steering console. Both of these compartments have drainage holes that allow any water they take in to drain directly onto the deck.
  • Sump basin conduits: Some Wahoo!s had a solid fiberglass bench seat that spans the width of the cockpit (in some models the seat contains a built-in fuel tank, in others, a cooler, and in some both). Since the seat blocks water attempting to run to the rear of the boat, these models include a conduit…a hole in the deck just forward of the seat that funnels water into a pipe that connects to the sump basin. Also, common in many models are two small compartments on either side of the stern. Wahoo! literature describes them as battery storage, or as optional coolers or live wells. it’s also a popular location for a fuel/water separator. Both of these compartments have drain holes that drain into the sump basin.
  • Sump basin: As stated, Wahoo!s with the self-bailing system includes a sump basin in the rear of the boat just inside the transom. Water is designed to drain into this basin and then exit the stern through a one inch scupper.  The basin varies in size with model. In my 1987 Striper 16.2 the basin is 18 inches long by 4.5 inches deep by 8 inches wide. Its capacity is about 2.5 gallons.
  • The scupper: The scupper is simply a tube that connects the sump basin to the outside stern of the boat. It consists of a through-hull PVC pipe (approximately six inches long and one inch diameter) with flanges at either end. Important to note: it is located below the water line.

Drain conduit forward of bench seat

The sump basin looking toward the bow. The hole is the conduit that drains the deck area forward of the bench seat.
 The sump basin looking to the stern. The top hole is the drain for the two rear compartments. The bottom hole is the scupper.

Years and models

I don’t have a list of the years and models that use this self-bailing system. A 1995 Wahoo! brochure that covers 19 foot and up models makes no mention of it. Yet I’ve spoken to owners of 2100 CCs who said their boats have it. All of the 16.2/1650s I’ve seen have it, as do all of the 1750 Offshores I’ve seen.

Problems with the design

While the self-bailing system may have been forward-thinking, in practice there are a number of issues with the design:

  • Most people simply don’t trust it. They are not comfortable with the below-waterline location of the scupper. That location means water enters the boat through the scupper when the boat is not underway.
  • People do not like wet feet. Even if you’re OK with some water entering the sump basin through the scupper, that water could easily slosh up an around out of the basin making the rear of the boat wet.
  • Contrary to Wahoo!’s implied claims, there are plenty of ways for water to enter the bilge. I’ll discuss this in detail in a post on the below deck drain system. But obviously water in the bilge, if not dealt with immediately, can cause major handling problems, as well as rotting the stringers and transom (Wahoo!s do use wood in their transoms, in case you were  wondering). There are several ways that that the self-bailing deck design can contribute to water in the bilge:
    • Cracks in the flanges or PVC tubes that drain the forward and rear compartments.
    • Cracks in the flanges or PVC tubes that channel water from the deck to the sump area.
    • Cracks in the scupper’s flanges or PVC tube.

 

Owner solutions

Different owners deal with the issues presented by the deck drain system in different ways, depending on their their comfort-level with the original design and whether or not they keep their boat in the water. Some options:

Solution 1 – Use it as is (no modifications): This could work fine if  you 1) Don’t store your boat in the water, and 2) Don’t mind getting your feet wet. This was the original design for the boat. In theory it should work even if you DO store your boat in the water. However few owners I’ve spoken to choose this route, regardless of where they keep their boat.

Solution 2 – Install a one-way scupper adapter. This is a flap that allows water to exit the scupper but not enter it. This solution could work fine if you 1) Don’t store your boat in the water, and 2) Don’t want your feet wet. The one-way adapter is installed on the exterior side of the scupper and opens to allow water to escape when underway but otherwise prevents water from coming in. This solution won’t work well for boats stored in the water because it won’t allow rain water to escape. Here’s an example of a scupper adapter.

Solution 3 – Plug the scupper when using the boat. This solution could work fine if you 1) Don’t store your boat in the water, and 2) Don’t want your feet wet, and 3) Typically don’t take on more than a few gallons of water topside when using the boat (and for times you do you could always just bail the sump basin). This was how the previous owner of my boat used it. Prior to each launch he installed a plug on the inside end of the scupper (plugging the outside makes even more sense). At the end of the day when the boat was pulled he removed the plug and it stayed out until the next launch.

Solution 4 – Plug the scupper and add a bilge pump to the sump area: This is the approach most Wahoo! owners who keep their boat in the water take. Plug one or even better both ends of the scupper and install a small automatic bilge pump inside the sump basin. This solution should address any above-deck water issues…provided the pump doesn’t fail!

My Solution

This is not a suggestion to do as I did but a record for what it’s worth. I store my Wahoo! in the water in a slip. Like a lot of owners, I am not comfortable with the self-bailing system. Specifically, I’m not comfortable with the notion of water entering the scupper when the boat is at rest. And I have concerns that it won’t drain properly during rainstorms–all it takes is a leaf blocking the scupper and your boat fills up with water.

So my solution was to plug the scupper and add an automatic bilge pump to the sump basin. To date I’ve just plugged the inside end of the scupper but next season I’ll plug the outside as well. (Why let water into the scupper where it could potentially leak into the hull?) For a bilge pump I installed a Rule Mate 500. That’s actually a lot more pump than the space requires. I chose it mostly because of its low profile (which allows me to keep the wooden lid on the basin)  and because its float switch is A) built in (I didn’t want to have to install a separate switch), and B) float driven rather than chip driven (hopefully less drain on the battery).

The hose from the pump I have draining into the splashwell. In order to keep the original Wahoo! teak lid on the sump basin, I would have had to drill a new hole in it (to allow the hose to pass through). But I really hate the idea of permanently altering a part that is no longer available. So I bought some 3/4″ x 3″ oak from my local lumber yard and fashioned my own slatted lid to the sump basin. It looks good and I have no problem drilling holes in it to my heart’s content.

The sump basin of my Wahoo! with a Rule Bilge Mate 500. The pump drains into the splashwell. (The hose you see coming out of the access port connects to a second pump in the boat’s bilge.)
 The sump basin with my homemade oak lid. I think it cost me $5 to make.

End Notes

So that’s a pass at explaining the Wahoo! self-bailing deck drain. It doesn’t answer everything yet. For example, I’d like to understand why the sump basin scupper was designed to be below the water line. Was that the only place it could go? Or was there a specific advantage to placing it there? Again, if you have questions, thoughts, information, or corrections please share them with your fellow Wahoo! owners.

Here are a few links to online discussions where you might find more info:

Next up: an attempt to explain the Wahoo! below deck drain system (a.k.a., “And here I lost my mind” :-)  ).