Eliminating water in the bilge

Wow, November already. The end of the boating season here in Boston. The weather’s been kind but for how much longer? An oddity–not a single hurricane came up the East Coast this year.

If you’re a regular visitor to the site you may have noticed the lack of posts this summer. Apologies. It was a frustrating season for me and my Wahoo!, although nothing to do with the hull itself. A series of engine problems coupled with a busy schedule kept the boat  out of the water until August. The silver lining is that the extra time the boat spent sitting in the driveway let me tackle some maintenance tasks I’d been meaning to get to. Chief among those was finding and eliminating the leaks from the deck into the bilge.  And I’m happy to say I got pretty damned close. So here’s a write-up.

The Old Water in the Bilge Mystery

Like many Wahoo! owners, I’ve been plagued by water–sometimes a lot of it–showing up in my bilge. The source of the water has been a mystery and a constant topic of speculation among Wahoo! owners. About the only things I knew for sure, because I keep my boat in a salt water slip and because the water in the bilge was always fresh, it that it was  coming in from topside. Any time I hosed down the deck or we got a solid rain I could count on finding a few gallons of water below. Following a three day deluge several years back I must have pumped out at least 40 gallons…that’s 300 pounds of water!

As a quick fix, a couple years back I installed a small pump in the bilge. That gave me a way to get water out. But ultimately I wanted to stop it from getting down there in the first  place. That meant a careful inspection to determine the possible sources of leaks, followed by a whole lot of patching and caulking.

About My Wahoo!

Before getting on to the how-to part of the article, a few points about my Wahoo!. It’s a 1987 16.2 Striper. That’s a 16 foot (thereabouts) tri-hull center console. Several hings about it that may differ from your Wahoo! model:

  • It has a sold fiberglass bench seat. The seat spans the width of the cockpit, separating (as far as deck water is concerned) the front and rear of the boat. A drain hole in the deck just forward of the  seat funnels deck water from the front to the sump basin in the rear.
  • It has a rigging tube located inside the console. There, steering cables and electrical wires enter the console from below deck through a hole in the floor. The rigging tube (really just a six inch PVC lip) sits over the hole. It’s purpose is to keep deck water from getting into it.

Looking for Leaks

Inspecting the boat, I didn’t see any single major source of water incursion. There wasn’t a big crack in the deck, a gaping hole, or anything like that. That suggested  water  was getting in from any number of smaller leaks: the decks drains, the rigging tube, access ports, screw holes, etc.. Going over the boat carefully and methodically and running some tests, here’s what I found:

  • The deck drain system, luckily, did not appear to be leaking. More on this a bit later.
  • I found some small holes I’d never noticed inside the rear storage compartments. there were maybe six in all,  and another one inside the sump basin. It looked like they’d been drilled by a previous owner to mount equipment now no longer present.
  • The rigging tube had a big chunk missing out of it and several smaller cracks, the result of years of cables being fished in and out.
  • Unfastening and then propping up the console, I found that the caulk where it met the deck was in bad shape. Also many of the holes for the securing screws had become enlarged, in some cases two to four times their original diameter, the result of years of pressure on them. Needless to say the screws in those enlarged holes spun freely and weren’t securing anything.
  • Everywhere the caulk looked old and in poor condition (e.g., the access ports, the rigging tube, hardware fittings).

Tips on Finding Leaks

Aside from visual inspection, here are some ideas on how to identify leaks:

  • Storage Compartments: For compartments, one way to test for leaks is to plug any drain holes and then fill the compartment with water. Obviously, if the water goes down, there’s an issue.
  • Rear Cockpit: Because my Wahoo! model has a solid bench seat, I was actually able to eliminate the entire rear cockpit area of my boat as a source of leaks by plugging the drain holes in the sump basin,  filling that area with several inches of water, then looking to see if it went down.
  • Deck Drains: I was lucky in that my boat’s deck drain system did not have any leaks. As a result, I don’t have specific advice on how to fix  your boat’s deck drain  system if its contributing to water in your bilge. (If there’s a reader out there with experience in this and you have advice to pass along, please let me know.)  But here are some ideas on how to at least test the drain system for leaks:
  • Start with a visual inspection of the flanges at the deck drain holes. Look for cracks, gaps, or a loose fit.
  • To test the seal where the flange meets the deck: 1) I plugged the  deck drain hole. 2) I poured about a gallon of water around it. 3) I observed it to see if the water went down.
  • To test for a leak in the plumbing below deck: 1) I started with a dry bilge. 2) I pressed the end of a garden  hose tight against the deck’s forward drain hole and then turned on the water and let it run for a minute or two. 3) I checked the bilge for water.
  • An alternate way to test the plumbing below deck: 1) plug the outlet hole where the deck drain empties into the sump basin. 2) slowly pour water into the the deck drain end until it backs up, indicating the pipe is full. 3) Observe to see if the water in the pipe goes down.
  • On one internet message board a poster suggested a test method that involved pumping smoke into the hull. It sounded too complicated to me, but it may be something you want to research.

The Repair Job

Based on my inspection:

  • I filled the old open screw holes I found in the storage compartments and sump basin using Evercoat Formula 27.
  • I recaulked all of the access ports (my boat has four) and the screws that secured certain deck fittings that I suspected needed it (namely, the fuel fill and the forward anchor locker)
  • I couldn’t find a replacement for the damaged rigging tube so I took it out and repaired it using fiberglass cloth. Then I reinstalled it, caulking well.
  • The enlarged holes for the console-to deck screws I filled using Evercoat Formula 27. Then I redrilled the holes to the size I wanted. I also installed screw anchors in all of the the console holes around, caulking them well as I sat them.
  • I scraped off all of the old caulk at the console/deck seam, cleaned up the area well, and then recaulked all the way around.
  • I found assorted small nicks and chips in the deck. These may or may not have been a source of leaks. I repaired them using either Evercoat Formula 27 or a dab of caulk. Not the most cosmetically perfect solution, but eventually I plan to recondition the entire deck surface anyway.
  • I also went over the console itself, caulking seams and repairing holes that would allow water to get inside, and making sure all gauges were mounted snugly.

That was it. Leaving out the setting time for caulk and the fiberglass cloth, the entire project took maybe four to six hours spread over a couple of days. The only part that was a little bit hard was removing the rigging tube, since that required unhooking all of the cables and wires that run through it. Of course, if the tube had not needed repair but only recaulking I could have done that without taking it out. As it was, I used the opportunity to straighten out some of the wiring inside the console that had gotten messy over the years. If you do need to remove a rigging tube, take careful notes on all connections as you unhook them, what wire goes where. Taking pictures as you go is also a very good idea.

A good caulk tip…that I got from my friend Dave. When caulking a place where two surfaces meet (for example, where an access port meets the hull) let the caulk set awhile before tightening things down. That allows the caulk to form a better gasket, whereas tightening down immediately tends to just squeeze most of it out.


After finishing my repairs (and after all caulk had had a chance to set completely) it was time to test the results. Starting with a an empty bilge I hosed the deck and cockpit down for a solid five minutes. I sprayed in about 35 gallons of water, making sure I got it everywhere on the deck and sides. Prior to the repair work a hosing like that would have put at least two gallons of water in the bilge. And after? The results exceeded my wildest  hopes.Turning on the bilge pump all that came out was about one cup.

In the months since then it’s rained a fair amount and I’ve hosed down the deck many times. Still no water below. The “mystery” of water in the bilge turned out to be a simple one with a simple solution. So if water below has been an issue for you, rest assured that it’s likely an easy fix, not to mention a great winter project for your Wahoo!


Addendum 11/6/14

Pulled the boat from the water today and parked it in it’s winter slip (a.k.a., my driveway). I powerwashed the deck for a solid ten minutes and no water showed up in the bilge. Amazing.


Wahoo! bilges: an explanation

As a companion piece to the post on the Wahoo!s above-deck drain system, here’s one on the Wahoo!’s below-deck plumbing. Like the self-bailing deck, the Wahoo! hull interior is one of the most confusing features of these boats. As with the post on the deck drain system, I’ll update this article if and when new info becomes available. Note also that this post deals specifically with smaller Wahoo!s–the tri-hull models. For all I know the larger Wahoo!s (say, those over 21 feet) and/or the V hulls had a very different design. So your mileage may  vary.

The Wahoo! hull: What’s in there?

Basic to understanding the design of a Wahoo! is knowing what’s going on insider the hull. Some key points:

Wahoo! hulls contain foam. This helps with buoyancy of course. Boston Whaler hulls are foam “filled.” The “filled” part means every bit of the hull interior is filled with sprayed-in foam. This not only maximizes buoyancy, it also in theory keeps water out of the hull because there’s no literally place for it to collect. But there are a few potential drawbacks to this design. For one, because there is the assumption of no water ever entering the hull, Whaler hulls do not have a drain plug. That means if somehow water DOES manage to get in there, there’s no easy way to get it out. A second concern is that over time the hull foam may begin to absorb water, not unlike a sponge. The water could come from the outside or it  could come from condensation inside the hull. Either way, as the foam absorbs water it takes on weight. That causes handling problems. And over time the moisture can cause the foam to break down.

Distinct from Whalers, Wahoo! hulls are foam “lined.” The “lined” part means that the top, sides, and bottom of the hull interior are coated with blown-in foam but there is an air cavity in between. Also the Wahoo! hull includes a drain hole in the stern. The advantage of this design is that the cavity allows the interior foam and stringers to “breathe”; that is, the ability to dry. And any water that does get into the hull can be drained. The downside, compared to the Whaler design, is that with less foam comes less buoyancy, and the air cavity allows water a place to collect.

Cutaway showing Wahoo! foam liner and air cavity.

The original Wahoo!s from the mid 80s design did not include a bilge pump. Since that time 25 years’ worth of Wahoo! owners have wondered why, because water certainly finds its way into Wahoo! bilges, as it does with any other boat. It’s not immediately clear what the the absence of a pump meant from the manufacturer’s perspective. Maybe it meant the company  had a misplaced faith that water wouldn’t get into the bilge. Or maybe it meant they assumed that most Wahoo!s would be used as trailer boats whose drain plugs would be opened after every use. Or maybe it was simply an attempt by the company to cut costs and leave it to customers to add their own bilge pumps. Whatever was behind the initial decision to omit a pump, it was not adequate. Within a several years Wahoo! brochures began mentioning an “optional” bilge pump.

How water gets into the hull

So does your Wahoo! need a pump in the bilge? First, let’s talk about the ways that water can get into the bilge. Leaving aside leaks in the hull exterior (but all the more reason for a bilge pump), you have:

  • Condensation (aka “hull sweat): If you store your boat in the water, condensation will form inside the hull. The amount will vary based on temperatures but can easily result in a gallon a week of water in the bilge.
  • Cracks in the deck drain system: The Wahoo! deck drain system (discussed in this post) consists of a series of deck flanges and below deck PVC tubes. It’s quite possible for these to develop cracks that allow water into the hull.
  • Power and steering cable deck port: On many Wahoo!s the power cables from the battery and the steering cables from the engine pass into the hull and then up into the console through a hole in the the deck. This deck hole can allow quite a bit of water in.
  • Access ports: Access ports, either original or after market, are notoriously leaky.
  • Other screw holes or cracks: Lastly, any screw hole in the hull, especially the deck, if not properly caulked, can allow water to leak in. After 25 years or so, odds are good at least some of the screws securing your console to the deck are not sufficiently caulked any more.

These things together or alone can allow quite a bit of water into you hull. Water is especially good at finding its way in when its got some force behind it, such as wind-driven rain or when you’re hosing the deck. Given the relatively small size and weight capacity of Wahoo!s, and that a gallon of water weighs seven pounds, it doesn’t take much to affect performance.

Adding a pump in the bilge

So to the question of whether your Wahoo! needs a pump in the bilge, I say the answer is, yes, absolutely. Even if you keep your boat on a trailer, the added safety and security that a bilge pump gives you make it well worth it. The installation is easy and inexpensive. I would not waste time considering a manual pump–put in an electric one and be done with it.

Locate the pump in the spot shown in the diagram above, at the rear of the bilge along the keel. This is the lowest section of the hull and where all water will run to. Most Wahoo! tri-hulls come with a five inch access port in the center of the stern through which you can install the pump. If  yours does not include an access port you’ll need to add one.

Here are a few notes on the pump I installed in case it’s helpful to anyone. There are certainly other ways to do it.

  • I chose just about the smallest pump possible, a Rule 360. It fit easily through my existing access port and its capacity in more than adequate for my 16.2 Striper.
  • I chose not to install an automatic float switch. But I can get away with that because the marina where I keep my boat is ten minutes from my house. So I can run over there any time to turn on the pump. If I had to leave the boat unattended for days or weeks at a time I would add a float switch or one of those chip driven pumps that cycle on and off checking for water.
  • For mounting the pump, I did not want to screw into the hull. One alternate mounting method I read called for gluing in a piece of marine grade plywood and mounting the pump on that. But I decided that was overkill. Plus it would have raised the pump up 3/8 to 1/2 an inch from the bottom, allowing that level of water to sit unpumped in the bilge. The simpler solution was to apply some 3M 5200 directly to the bottom of the pump’s basket and glue the basket right to the bilge floor. In 10 minutes I had a well-fastened mount that isn’t going anywhere.
  • The hose I ran it straight up and out of a hole I drilled in the access port cover. Like the pump I installed in the deck sump basin, the bilge pump drains into the splashwell.
Rule 360 bilge pump. Hose from bilge pump exists through hole in access port cover and drains into splashwell..

A one pump system?

Just as I was finishing this post I wondered whether anyone had ever configured his Wahoo! so that a single pump handled both the above and below deck drainage. You could achieve this pretty simply by installing a pump in the bilge and then drilling about a  one inch hole in the bottom of the deck sump basin. That would dump all water that enteredd the boat into the bilge. It seems like a bad idea for a few different reasons, but man if anyone has ever tried it I’d love to hear how it went.

More reading

Here’s a little more reading on the subject:


(Note: in this message thread Monstawhala states that the top hole in the deck sump basin drains into the bilge, and that both stern compartments also drain directly into the bilge. That is not correct. The stern compartments drain into the sump basin via the aforementioned top hole in the sump basin.)

Wahoo! self-bailing decks: an explanation

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).) Continue Reading…