OWNER ARTICLE: Through-Hulls, Baitwells, and Washdowns


Contributing Member


UPDATE 6/02/2008: The through-hull Installation described in this article has received approval from Triumph. This means that the hull warranty will not be voided by the procedure provided it is done exactly as described in this article. This procedure can also be used to install Through-hull transducers.

Some of the photos are posted, however, my arms really don't fit through the deck plate, so I am switching gears to look for a hatch before finishing this project. Please consult with your local Triumph Dealer or the Factory before making any cuts in the hull of your boat.


Howdy Y'all! I'm Frank Dixon, owner and operator of Princess Anne Marine Services in Virginia Beach, VA. I am a Certified Marine Electrician with 10 years experience covering almost every aspect of boat repair and maintenance. This article is part of series covering the modifications I am making to my 2003 Triumph 170 CC.

The first topic we will be discussing is going to be the installation of a high-speed pickup for a new baitwell pump, the installation of the pump itself, and also the installation of a raw-water washdown system utilizing the same through-hull.

Skills that will be used in this project are Layout and Design, Marine Electrical, Marine Plumbing, Plastic Welding, and adaptation of Basic Carpentry. The skill level required is average. The time required is 1 day. The Price range is $300-$450, depending on brands used.

Materials Needed

  1. Shurflo Piranha Livewell Pump & 800 GPH & Model# 357-113-10 or equivalent Dual-Port live-well pump
  2. Shurflo Pro Washdown Pump & 4.0 GPM & Model# 4903-4282 Includes Coil Wash-down Hose& Strainer or equivalent
  3. (2) Shurflo Pump Adapter 90˚ 3/4" Hose -- Model# 94-181-11 or equivalent
  4. 1/2" MPT to 3/4" Hose adapter or 1/2" MPT to 3/4" Barb 90˚ Adapter, 1/2" FPT "Tee" Connector, 1/2" NPT Close Nipple, 1/2" NPT Small Ball Valve, 1/2" MPT to Garden Hose Adapter
  5. T&H Marine Wash-down Fitting with Shutoff Valve & Model# WDV-1
  6. Forespar Marelon Scoop Strainer -- 3/4" MPS -- Model# 906059
  7. Forespar Marelon Seacock -- 3/4" FPS -- Model# 904010
  8. Gilmour Twist Nozzle & Model# 528GF or equivalent will replace wit htwist plastic nozzle when I can find one
  9. 15' 3/4" Reinforced Clear PVC Hose
  10. 6 All-Stainless Steel Hose Clamp for 3/4" ID Hose AWABS Clamps are highly recommended
  11. 15" 16 AWG Safety Duplex Marine-Grade Tinned Wire
  12. .090 Crimp Sockets for Deutsch Connectors
  13. Electrical Terminals & Heat Shrink I prefer Double-Crimp terminals with Heat Shrink over them to Terminals with Heat Shrink already on them.
  14. 15 Amp Push-Button Circuit Breaker with Black rubber Cover If your boat uses fuses, a 15 amp quick-blow fuse is required instead
  15. 15 Amp toggle switch with Black Rubber Boot or 15 Amp rocker switch depending on Boat Model and Year
  16. Sailing Systems Int'l Fire Extinguisher Box & Model# 49850000
  17. 4 1/2"x 4 1/2" x "¾" Polyethylene Lumber & I used King Starboard
  18. (3) #12 x 3/4" Stainless Steel Pan Head Sheet Metal Screws for Seacock
  19. (4) #8 x "½" Stainless Steel Oval or Flat Head Sheet Metal Screws for Scoop Strainer
  20. (4) #12 x 1"Stainless Steel Pan-Head Sheet Metal Screws for Washdown Pump
  21. (6) #8 x 32 x 1" Stainless Steel Pan Head Machine Screws, Washers, and Nylock Nuts for Storage box
  22. (3) #10 x 24 x 3/4" Oval Head Stainless Steel Machine Screws, Washers, and Nylock Nuts for Washdown Fitting
  23. Teflon Thread Tape
  24. Sudbury Elastomeric Sealant
  25. Polyethylene Welding Rod Unfortunately my dealer didn't have this, so I have to use Clear rod that I already had.
  26. Assorted Hex Drivers optional -- for hose clamps
  27. #2 Phillips Head Screwdriver
  28. Flat Head Screwdriver
  29. Drill
  30. #30 Drill Bit a 1/8" bit will do.
  31. "¼" Drill Bit
  32. 3/16" Drill Bit
  33. 1 1/8" Hole Saw
  34. 4 1/2" Hole Saw
  35. Roto-Zip or Jigsaw & Dremel Tool
  36. V-Groove bit for Dremel Tool (It will fit the Roto-Zip also)
  37. Measuring Tape
  38. 80-grit Sandpaper
  39. Fine- or Ultra-Fine Point Sharpie
  40. Acetone
  41. "¼" x 20 x 3" Bolt with Fender Washer and wing-nut to act as a clamp when installing Backing Block
  42. Plastic Welder & I use the 5600HT Airless Welder from Urethane Supply Company
  43. Wire Cutters -- Diagonal Cutters acceptable
  44. Terminal Crimpers & Ratcheting style preferred
  45. (1) Adjustable Wrench or Channel-Lock Pliers with at least 2-1/2" Jaw
  46. Socket Set

The Hose Nozzle came from Lowe's Home Improvement Warehouse. The T&H fitting should be available through special order at Bass Pro Shops, if not, I stock them. The welding rod and sealant are available through your local Triumph Dealer. The rest of the supplies are available through West Marine, Defender, or Boater's World. For the Hose adapter assembly, I bought another T & H Fitting and took the valve off of it and threaded it into the Tee with a 3/4" MPT to 1/2" FPT bushing and a 1/2" NPT Close Nipple.

Planning Out the Project

First lay out the materials and make sure you have everything needed. Trust me, there is nothing more frustrating than applying sealant only to realize you are short a screw. Then, gain access to the following areas: the compartment where existing baitwell pump is located (for the through-hull and baitwell pump), the area under the console (the washdown hose and electrical connections), and the aft port storage compartment (mounting the washdown pump). Make sure there is nothing in these places that will prevent the new equipment from being mounted or restrict your access while working.

The new through-hull will be located 6" forward of the existing baitwell through-hull, on the flat part of the inner hull. The washdown pump will be mounted vertically on the inside of the transom in the aft-port storage compartment. The washdown hose will go in the Fire Extinguisher box on the side of the console.

Once you are comfortable with the location of the components and you have verified you have the necessary materials on hand, it is time to begin working.

Removing the Existing Pump

We need to locate the existing Bait-well Pump and the associated through-hull. To locate the pump, unscrew the deck plate located in the splash well at the stern of the boat. Once this is open, look down and to the left and you will see the pump. If you are in the boat facing aft, the pump to the right is the Bilge Pump; we will leave this alone for now. Ok, now that we have located the pump, we need to find the through-hull. Stand on the ground facing the transom. On the right side of the motor, about a quarter of the way up the transom from the bottom you will see a wire-mesh screen covering a through-hull. This is the Bait-well pickup. If you have modified this in the past or are doing this project on a boat other than a 170 CC, the location for the pump and through-hull may be different. So, first thing we need to do is remove the filter screen. Hang on to it for future use if you'd like; if you are going to discard it, mail it to me. Next remove the nut holding the through-hull in place. You may need to get someone to hold the pump to keep it from turning. Be patient as the sealant will release slowly. Do not use a chemical like Anti-Bond to release the sealant; as such chemicals will weaken the Ropelene Hull. Once the nut is removed, climb back in the boat, and located the wires supplying electricity to the pump. A word of caution here, make sure the pump is disconnected from the electrical system. Disconnect the Deutsch Connector for the Baitwell Pump and disassemble the connector. Cut the pin sockets off the wires and remove the green seals. Save these, you will nees them to install on the new pump's wires. Next, unscrew the hose clamp securing the bait-well water hose to the pump and slide the hose off of the barb fitting. I found this easier to do with the pump pulled out of the deck plate. Once the pump has been disconnected from both the Electrical and Plumbing systems, remove the pump from the boat.

So now you are sitting there asking yourself, "What does this guy plan on doing with this hole in my transom?" Simple, ok - not really because of the access restrictions, plug the hole with Spin Welds or King Starboard plugs welded into place.

Installing the Through-Hull

Ok, now we are going to start the fun stuff. Take a deep breath and Relax! Yes, you will be drilling a 1-1/8" hole in your nice indestructible Triumph hull. No, if done the way described in this article it will not damage the integrity of the hull. And remember, measure twice & cut once. Let's talk through the cutting process before we actually do it, so we are comfortable with how it is going to proceed. The overall goal is two-fold. One goal is to end up with a 1 1/8" hole cut at a right angle to the hull exterior in which we will mount the new through-hull. The other goal is to have a reinforced location that we can mount the seacock flange to. To do this we are going to first locate where we need to drill, then we will make a cutout on the inside of the hull to accept the backing block for the seacock. After that we will drill the hole for the through-hull fitting through the outer hull and backing block, install the pickup in the hull, screw the seacock onto the through-hull and secure it to the backing block. If you have further questions about this process seek answers before beginning any cutting on your boat.

Measure 6" off the inside of the transom inline with the former Baitwell through-hull and parallel to the keel then transfer that location to the hull exterior. It will be easier to drill at the proper angle if we work outside-in versus inside-out. Also, a portable Drill Press attachment on your drill will help tremendously. We will then drill a 1/8" Pilot hole through the outer and inner hull. Double-check where the hole came through inside the hull. It is easier to relocate the pilot hole than patch the actual hole for the fitting. If it is in the right location, re-drill it with the "¼" bit, this will help guide the hole saw later. If not, re-drill the pilot hole in the correct location before drill with the larger bit. Next we will take our 4 "½" hole saw and drill from the inside of the hull out until we reach the inside of the outer hull. It is very important you do not penetrate the outer hull, but if you do, repair it before proceeding.

Let's take a time-out from the boat and head over to the workbench. Remember that piece of Polyethylene you have? We are going to use that to fabricate our backing block for the seacock. Draw a 4" x 4" square on the block, mark the center, and drill a "¼" hole. We will use this hole to center our circular cutter for our Roto-Zip and later to center the block on the location of the through-hull. Now cut out the circular block and sand the edge fairly smooth with 80-grit sand paper. Also, sand both faces to allow the sealant to better adhere.

There are three options for securing the block to the hull. The first is tp "glue" it in place with sealant or Scotch-Weld for Plastics, the second is to weld the block to the hull, and the third is to do both. I am opting for the third method, as I feel it will provide the highest amount of strength when we are done. Ideally, we would have a way of chemically welding the block to the hull; however, polyethylene doesn't lend itself to chemical welding. So, that being said, make a face the bottom of the block, measure "¼" in from the outside edge and make marks around the circumference of the block. Next, measure 1 1/8" in and marks this also around the circumference. We will apply the sealant in the space between these two marks. Before applying any sealant, however, we need to prep the spot on the hull where we are going to install the block. To prep the location, first cut the floatation foam back about 1/2" to allow additional clearance for the welder. Then lightly sand the exposed hull to allow additional bonding with the sealant. Ok, back to the sealing. Apply sealant sparingly to the back of the block in the space between the two marks. We want just enough sealant to facilitate bonding, but not enough that is spreads into the area we are going to weld. The easiest was to do this is with a Popsicle stick or plastic mixing stick used for mixing resins. Squeeze out a small amount of sealant and spread it thinly over the block. Place the block sealant-side down against the hull. Place the "¼" bolt into the hole from outside the hull in, place the washer on the inside, and tighten the wing nut down. This is going to clamp the block to the hull until the sealant sets-up. If it's getting late or the misses is starting to yell at you for spending more time with the boat than her, now is a good place to stop. After all, we have to let the sealant do its thing. Me, I'm going crack open an ice cold beverage and relax.

Well we've come back and found our backing block firmly glued in place in our boat. So we need to remove the bolt, break out the 1 1/8" hole saw and make the cutout for the through-hull to slide in to. And no, I haven't forgotten about the welding, we'll get to that in a little while. This hole can be done from the inside or outside of the boat, whichever you prefer. I like to cut hole for through-hull from the outside-in just because I have more room and I'm not a small guy. So, carefully line up your hole saw in the "¼" guide hole and drill straight through the hull and backing block, being careful to drill at a right angle to the outside of the hull. Once this is done, go ahead and dry-fit the through-hull. Now is the time to find out if there are any problems. It will be a pain to remove the block after it is welded into place. If everything fits correctly, mark the location of the screw holes for the scoop strainer on the hull then remove the through-hull.

Carefully cut out a v-groove between the block and the hull around the hole cut for the through-hull. This will add more surface area to the weld. Carefully, with your plastic welder, weld the block to the hull around the v-groove. Also, use a fillet weld to secure the outside edge of the block to the inside of the hull. At this point you can take a little creative liberty if you would like and fill the space around the block with 20# density flotation foam and the cover it with plastic welded into place or you can leave it as is. I am going to cover it, the plastic I use will come from the 4" hole cutout. This will prevent water that finds its way into the bilge from migrating into the foam.
Well at this point you should have something that looks like the above picture. If not, take some shots and send them to me because we need to figure out how to fix it. If we match, then let return to the bottom of the hull. Remember those screw holes we marked? Grab a #30 drill bit, and drill those holes approximately "½" deep. If you go through the hull don't worry. Also, the two closest to the through-hull will be in the backing block. Grab you through-hull and dry fit it one last time, this time screwing on the seacock to see if we need to trim the through-hull's threads down. If we do, mark the amount to cut off and remove it. Before applying any sealant, refit the Through-hull and seacock assembly. If everything lines up, we can go ahead install it. To do this, we need to apply sealant in four places. First apply sealant to the four screw holes we drilled in the hull. Next, apply sealant around the neck of the through-hull where it meets the scoop and also around the flange of the strainer. At this point slide the through-hull into the hole and secure it with the four #8 Oval Head Screws. Now climb in the boat and apply sealant around the through-hull where it comes through the backing block. Also apply a small amount of sealant to the mounting flange of the seacock. Screw the seacock down onto the through hull until it is firmly against the backing block. Now carefully drill the holes for the screws securing the seacock flange. You may want to use a drill stop here, because you only want go 7/8" down from the top of the flange to prevent drilling through the hull. Fasten the flange to the backing block with the three #12 Pan Head screws.


I would recommend checking for leaks before proceeding. The easiest way to do this is back the boat down a launching ramp until the stern of the boat begins to float. Make sure you close the seacock beforehand; otherwise you will learn how fast water can enter a boat through a "¾" hole. Check thoroughly inside the boat around the seacock for any sign of water intrusion. If you aren't close to a launching facility, remember to conduct this test next time out before pulling the boat off the trailer. Now you are done with the hardest part of our project.

Installing the Baitwell Pump

This next part is fairly simple. Take the baitwell pump and screw it into the top of the seacock. Use Teflon Thread Sealing Tape on the threads before assembly. Also, make sure the outlet ports on the pump are facing up from horizontal. We don't want water to be able to siphon in to our plumbing when we are at rest. Any angle above level will do, so you can use whatever position works best for your particular installation.

Once the pump is in place, find out where your baitwell hose ran off to and slide it on the pump outlet. Secure the hose in position with an all-stainless hose clamp. Also, again with Thread Sealing Tape on the fitting, screw the 1/2" FPT T Fitting into the threaded port on the pump base, thread the ball valve and hose adapter into the top of the tee (this is optional, it allows you to flush the system with a garden hose to clear debris from the through-hull strainer and also to winterize the washdown system), and thread the "½" MPT to 3/4" Hose adapter into the other side of the tee. This is what we will attach the washdown plumbing to.

Remember those green wire seals I had you hang on to way back when? Now we get to use them. Take a look at the mating connector to verify which wire goes in which side. The Brown wire (12vdc+ from Switch to Pump) should go in side "A" and Black (12vdc-) should go in side "B". If you are not going to reuse the connector, use the following method to attch the Pump's wires to the boat's wiring. One at a time, starting with the Pump Power Supply (12vdc+, Brown), cut the connector off, strip the remaining insulation back approximately 5/32", and crimp on the connector of your choosing. I am using double-crimp quick-disconnect terminals so that when the pump needs replacement, I don't have to cut the wire back further. Next, cut the other wire out of the connector, strip back the corresponding wire on the pump and crimp on the mating terminal. Another trick here, if using any type of disconnect, crimp the male on the Pump's 12vdc positive wire and the female on the Pump's 12vdc negative wire. This will prevent accidentally hooking the pump up backwards. Now repeat the process with the other wire, and before connecting the pump, slide a length of heat-shrink tubing, cut long enough to cover both terminals with about 1/8" overhang on each end, over a connector on each wire of a circuit leg. Connect the terminals, slide the heat-shrink tubing so it is centered on the connection, and shrink it down on to seal the connection. If re-using the Deutsch Connector, the simply slide the wire seal over the wire, crimp on the socket contact onto the wire and seal, and slide the wire into the correct position in the connector. Repeat this process for the other conductor, re-assemble the connector, and plug it in to the mating connector.


The last thing to do with the baitwell pump is to test it out. Again, do this with a water supply for the pump, as most baitwell pumps are not designed to run dry, and a more common sense reason, it allows you to make sure the pump is pumping water into the bait-well. If everything checks out, pat yourself on the back, you've done well.

Installing the Washdown System

This will probably be the longest part of our little project in terms of time needed to complete. We are going to do this a bit out of sequence. I like to do all of my cutting before I begin installing, that way I can clean up and not be working around a lot of dust, or risk damaging something by cutting it accidentally. That being said, let's move up to the console and take a peek at our next step.

If you're boat is like mine, the Fire Extinguisher was mounted under the helm instead of in the holder. More than likely though, it's in the holder right where it is supposed to be. So there are three options: move the extinguisher to a location under the helm and use the now-empty holder, make a cut out on the other side of the console for a storage box, or mount the hose connection somewhere else on the boat. One creative place I have seen is in a tube in front of the console between the windscreen and baitwell. Where exactly you mount the hose is purely subjective, I chose to make a cutout on the left side of the console for a storage box as I am replacing the existing extinguisher box with a netted coaming box. Where you put the hose is up to you.

The process of modifying the Fire Extinguisher box to hold a hose is fairly straight-forward. Simply open the box you purchased, drill a 1 1/8" hole in the back of it, and screw the T&H Hose Fitting over the hole. Next, make an outline of the the recessed portion of the box on the port sidde of the console, and cut it out using a jigsaw or roto zip. Dry fit the new one and mark any new screw holes that need to be made. If you have an older boat with the rod holders in front of the console, the back of the box may press against the farthest-left holder. The box will screw in without problems, you just need to apply some pressure. Drill the screw holes, and dry fit the box again to make sure everything lines up and is square. Now take some sealant and apply it sparingly to the back of the mounting flange on the box. Press the box into position and secure it with the screws you removed earlier. Be careful not to strip the holes out, it would be best to use a screwdriver to tighten them instead of a drill. An even better option would be to replace the sheet metal screws with machine screws secured by washers and nylock nuts on the inside of the console.
Next we need to mount the switch and circuit breaker. Measure the spacing of your existing switches. You will to take measurements between switches and from at leas two edges to a switch. Once the spacing for the new switch and breaker have been determined, mark those locations with your Sharpie. Next drill the required hole for your switch (toggles require a 1/2" hole, push button breakers a 3/8" hole, and rocker switches a rectangular cutout). Install the switch and circuit protection device in the corresponding hole. If using toggle switches and push button breakers, set the rear nut so that the switch comes even with the face of the front nut. This, of course, does not apply to rocker switches.

Let's head back to the transom. We need to determine exactly where to mount the washdown pump. I chose to put it in the aft-port storage compartment, mounted vertically on the inside of the transom. The strainer is mounted under the splashwell overhang above the fuel tank. The key here is mount the pump as high as possible, with the motor above the pump head. This keeps the pump motor out of ordinary bilge water and if the pump seals should fail, keeps wate from leaking from the pump head into the motor. Mark the location of the mounting holes, remove the pump, and drill pilot holes on the mark with your #30 bit. Re-drill the mounting holes to size with a 3/16" bit. Before mounting the pump, screw the 90˚ Wing-nut fittings to the inlet and outlet, you do not need to seal the threads. Now fill the mounting holes with sealant, place the pump against the bulkhead, and screw it into place. Once the pump is in place, mount the strainer, then measure and cut the hose needed to plumb from the filter inlet to the outlet port on the baitwell pump base and the filter outlet to the pump inlet. Secure all hose connections with hose clamps. Take the rest of the hose to the console, access the space under the console, an feed the hose down through the wire pass along the hull under the fuel tank to the pump well beneath the splashwell. It may take a few tries to get it, and you may need to employ a fish tape to pull the hose through. Once the hose is in place, attach one end to the pump and attach the other end to the hose fitting on you newly installed storage box, again securing with hose clamps. Just an aside about clamping. I highly recommend double clamping all hose connections below the water line. Doing this correctly provides redundancy should a clamp loosen. However, none of the fittings we are using are long enough to allow double clamping.

The last thing we need to do before testing out our work is build the electrical system for the washdown pump. The easiest thing to do is run a single duplex wire from the helm to the washdown pump. The downside to this is it means a longer circuit, and more wire equals more money, and in some cases, larger wire. But, this is a relatively small circuit, so I'm going with the duplex wire. Let me explain the choice of wire size. First, I need to know how much current (expressed in amps) my pump motor draws. This is stated on the pump label and is 9 amps. Next I need to know how long my circuit is. DC circuit length is determined by the length wire needed to connect the power source to the appliance and the appliance to a negative bus. The power source can be a battery, converter, or in our case, a distribution bus. The negative bus is usually the negative terminal on the battery on boats this size, but I've added one under the helm in forsight of projects such as this. You can get information on that installation in my Electronics article to be published later this year. Anyway, for a circuit this size, a guess of length will suffice. I'm thinking it's probably ten feet each way, and I'm going to add five feet for a margin of error. that gives me a circuit length of 30 feet ((10+5)x2). The last thing you need to determine conductor size is allowable voltage drop. This is a non-critical circuit, so I will size the wire for a 10% drop, or 1.2 volts. Now I take the Length (30), multiply it by the current draw (9), and a constant K (10.75) to get 2902.5. Next I divided that by my voltage drop (1.2) to get my minimum wire size of 2418.75 cm. This translates to roughly 16 AWG wire, which works out well as 16 AWG is the smallest conducter size allowed per ABYC standards for power circuits outside electronics. Snoop around under the console and locate the string in the rigging tube leading aft. Secure the string to the wire and pull the wire through to our newly named pump well. Route the wire to the pump leads and connect them starting with the Pump Power Supply (12vdc+, Red), strip the wire back approximately 5/32", and crimp on the female double-crimp quick-disconnect terminal Next, strip back the corresponding wire on the pump and crimp on the mating terminal. Repeat the process with the 12vdc- (Yellow) wire, and before connecting the pump, slide a length of heat-shrink tubing, cut long enough to cover both terminals with about 1/8" overhang on each end, over a connector on each wire of a circuit leg. Connect the terminals, slide the heat-shrink tubing so it is centered on the connection, and shrink it down on to seal the connection. You may wonder why the pump wire for the bilge pump is brown and the pump wire for the washdown is red. Remember, brown connects the switch to the pump motor, since the washdown pump is really controlled by a pressure switch mounted on the pump, all our wire is doing is supplying accessory power to the pressure switch. Therefore, the wire should be either red (dc positive) or orange (accessory feed). Red and Yellow duplex wire is a lot easier to find than orange and yellow. Secure the wire up out of the bilge as best as possible and exit the area. Seriously, we are done working in this part of the boat so you can go ahead and close the deck plate. Crawl back under the helm and route the wire up towards the switch panel. Strip back the outer insulation so that there is enough of each insulated conductor have the negative route the the negative bus and the positive route to the helm switch. Trim the conductors to the required finished length, strip back the insulation about 5/32" (length is not important, you want to have enough wire exposed to see the wire on the ring side of the terminal but not enough to enter the ring area). Crimp on the terminals, cover them with heat shrink tubing, and heat it until the tubing contracts. Now attach the positive wire to the circuit side of the switch. Take a small piece of the scrap Red wire, strip the ends, attach terminals, and make a jumper from the circuit breaker to the supply terminal on the switch. Now take the remaining red wire and make another jumper from the circuit breaker to the supply side of another breaker. Last, connect the negative conductor to the negative bus. If you have a diapraghm pump like I used, they can be run dry. Flip the switch on and walk back to the pump, it should be running.
All that is left to do now is connect the Coil hose to the fitting inside of our box and make sure everything fits. Lauch the boat and again check for leak around the through-hull, around any hose connections, and around any threaded plumbing fittings.


Hopefully everything works as it should at this point. All that is left is to Have Fun and Enjoy Boating!