How to Install Thru Hull Fittings - TruDesign | Sailing Sunday

We replaced every Thru Hull and Seacock on Sunday with TruDesign.
This is a simple step by step guide on how we did it.
-- Before you start --
Your existing seacocks should have the size printed into it, 1/2" or 1/4" or 1 1/4" etc... All you need to do is write down these sizes and order the new parts. TruDesigns website (Below) is very helpful and easy to navigate to find all the fittings needed.
Tools & Materials Required:
Safety Gear, Grinder, Silicone Gun, Scraper, Spanner and/or Multi-Grips, Hammer, Fine Sandpaper, Sander, Drill with small grinding stone (not essential), SIKA 291i, some old bung plugs, Turps and old rags.
STEP 1:
Using your grinder, carefully grind off all the old thru hull fittings as seen in this video. Then wiggle loose inside the boat while gently tapping an old bung plug into it from the outside until it releases from the hull.
STEP 2:
Scrape off the excess sealant and then sand either by hand or using a small mouse sander. I used fine sandpaper and along with a small grinding stone in my drill to gently clean excess sealant around the inside of the hole. Bring it back to gelcoat ready for the new thru-hull fittings.
STEP 3:
Remind yourself why you're doing this!
STEP 4:
Test fit your new thru hulls are correct before gluing down, if you have trouble fitting them you can remove the handle for installation and screw back on once completed. You may need to adjust a few things eg, measure and cut your thru hull fitting for the correct fitment depending on your hull thickness. You can use a hacksaw to cut them down, I used a grinder.
STEP 5:
Clean all the surfaces and thru- hulls with turps ready for install and apply your sealant, we used SIKA 291i throughout the whole process. Put a small amount around the ring of your thru-hull fitting and push in with a slight twist clockwise. From the inside, I put a small amount around the base then installed the washer and nut hand tight. Finally cleaned off any excess and left to dry overnight.
STEP 6:
Don't stress!
STEP 7:
Tighten the final turn the following day.
STEP 8:
Connect your seacocks by using SIKA 291i or any other sealant you choose. Don't be shy, put a good amount around the thread and tighten up your seacock to the desired position and leave to dry. Repeat the process when screwing on all your fittings, and use 2 new hose clamps on all hose connections. We used SIKA 291i throughout the process, but you can also use 3M 5200, 5200 fast cure, Loctite 5331, or plumbers tape on the threads. We did it all at once and left it all to dry, but you can put the seacocks on first leave to dry then connect the hoses up the following day.
FINAL STEP:
Grab a Beer you've earned it!!!
--- TRU DESIGN ----
www.trudesign.nz.
The though hull fittings and seacocks we used were from TruDesign made in New Zealand. For more information check out their website! We have heard great things about them across many countries and now after installing them, we highly recommend them ourselves!
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[@Conks01]

What a great video. Quick, informative, to the point. What more could you need. Good job

[@SailingSunday]

Thank you 😊

[@easemailboxes]

Doing a boat up now and know nothing about boats (learning fast!) Adter pulling down a transom and finding how badly done a previous repair was made (silicone etc) and then watching your video , it really helped the confidence!

[@SailingSunday]

Yeah, the boatyard sometimes aren't always the best.... They just want to get the job done quickly and move on quickly to the next job!

[@weburnitatbothends]

Thanks for the share mate, I am at the point of deciding what I am going with and have found it hard to get my head around trudesign not being any type of metal. To Team TruDesign - I will be buying some in the near future :)

[@SailingSunday]

Im stoked they aren’t metal, many old school sailors don’t like them and say they would never have these glass composite stuff under the water but forget the depth sounder and speed wheel are both plastic 🫣

[@marioracicot3699]

Hey Buddy,. You probably won't read this since you taped this 2years ago... But I m rebedding my depth sounder and wanted to see a video...KZbin selected you! Your video helped me. Thanks!

[@SailingSunday]

Thats so awesome!!! Super stoked it helped :)

[@Toob41]

Perfect, answered all my queries - thanks! Your video is used on Trudesign's own website as an instructional video, well done.

[@SailingSunday]

Oh wow, that’s so awesome!!!

[@rickvideo1]

Nice job. One tip when using Sikaflex for bedding is to let it set for a short time so you don't squish it all out. Time is based on temp, humidity etc.

[@SailingSunday]

rickvideo1 I didn’t actually let it sit initially but only because I was just doing it up hand/finger tight first anyway, then waited the next day to tighten up completely. Would you suggest it’s better to let it sit initially still?

[@rickvideo1]

@@SailingSunday seems like you did it right, just a different approach. Good job!

[@SailingSunday]

​@@rickvideo1 Awesome, You had me worried for a minute there haha!! 4 months on and we're still floating lol!

[@Paul_Crosbie]

Nice video - thanks for taking the time to put all the information together 😀

[@SailingSunday]

My pleasure, glad it was helpful!

[@alanmctavish3628]

I appreciate your brief instructions.

[@simonjconnor]

Good job and looks like you have a lovely boat there. This is the first video I've seen and will start watching more. I plan to replace my raymarine thru hull speed housing with on my next opportunity with one that has a water retaining valve and your video gives a little more confidence on how to do that. Cheers.

[@SailingSunday]

Awesome thanks for watching, welcome aboard!!! :) Yes, it was very easy, for me being in the building industry since I finished high school, I was a little nervous messing around with holes that keep a 14 tonne boat afloat but once I did the first one, it was really quite simple!!! lol

[@jonathanomgitsme]

Just what I needed for my first thru-hull install, esp the grinding wheel to clean the hole. Cheers!!

[@SailingSunday]

Right on! Glad it helped!

[@simonbondethornsen6163]

Greetings from Denmark, the beat diy on the tube!

[@SailingSunday]

Thank you! Glad you enjoyed! 🙂

[@nordemoniac]

If you have a normal thru hull, hammer in a bung plug, saw it flush, then use a hole saw to cut the flange off. They recommend teflon tape on the threads, it should be enough, but I like the idea of using sikaflex/3M 4200 as it’s still removable, but will bond better. Creating that “o-ring” effect by waiting a day before tightening isn’t always the best method, sometimes the sealant could rip/loosen up.

[@RudiRednoseChannel]

Great Video - thanks for sharing 👍👍. Cheers, RR

[@SailingSunday]

Thanks! 😃

[@DirkJacobsz]

Take a bow - how to do it in 5 min. Thanks man. onya mate

[@SailingSunday]

Thank you 🤙😊

[@Brat-xx8ss]

Thanks! have my first little boat and i needed a nice quick guide like this :)

[@SailingSunday]

Glad I could help!

[@sailingsalaciastar]

Thanks, I'm not sure that it is as easy as you say but I will definitely give them a go now.

[@SailingSunday]

Sailing Salacia Star it’s so easy! Sanding anti-foul and painting was much harder!😂

[@jackyofalltrades9875]

Thank you for this video!!!

[@SOLDOZER]

Dont put a strainer over it on the outside. In an emergency you won't be able to plug it from the exterior, its much harder to clean the barnacles, etc.And in an emergency you can use a Seabung.

[@SailingSunday]

That's true, I was thinking of my chances though, I reckon there's a much higher chance of sucking up a jellyfish, plastic or weeds then a catastrophic emergency. But you are definitely right there, I hope I don't eat my words in the future!!!!

[@bertdom5707]

Yep….strainer on the inside after the valve……

[@SOLDOZER]

@@SailingSunday Revisiting this thread I had my raw water pump suddenly quit in the middle of the Gulf Of Mexico. My first thought was I sucked up plastic or a jellyfish and wishing I had a strainer I could have at least eliminated that theory.

[@TonicOceanis50]

Thanks for sharing....

[@ianrix4442]

GREAT LITTLE VIDEO HOPE TO BE ABLE TO GET MINE DONE SOON LOL

[@SailingSunday]

Thanks Ian!!! Yes, hopefully soon! lol Highly recommend before you guys go back in the water! If you need any advice, let me know!

[@sukysailsfree]

Great video. I am replacing Marelon thru hulls .. why use Trudesign versus Marelon. And if I do replace with Trudesign, will sizing be an issue.?

[@sailingavocet]

great and informative video! Cheers ~

[@SailingSunday]

Thanks guys! Looks like you guys have been working hard also! Hope you're all safe and healthy!!!

[@alannorthcott6651]

Pick the "chippie"...haha great video!!

[@SailingSunday]

alan northcott Thanks! 😆

[@user-iv8jm8tn5n]

I have a question in regards fitting these on metal boat. Our boat is currently out of water and has been recently painted and antifouled. Do we have to strip the antifouling paint before the installation? If so we install the Thru Hull fittings on bare metal with the recommended silicon only or do we use a primer and then silicon? If primer is necessary could you please recommend a type of primer we should use? Thanks ...

[@sailingsvtesla9052]

I've seen a few sea-cocks replaced on KZbin and have a question about the interior of the hole... would epoxying the hole to help prevent moisture intrusion be something I should do?

[@SailingSunday]

RJs Salty Adventures It definitely wouldn’t be bad to do, but I wouldn’t bother, the sika 291i completely sealed everything. For me it oozed out everywhere, covering everything essentially sealing it all and moulding it to be part of hull.

[@nordemoniac]

Epoxying the actual thru hull in instead of sealant makes it “one” with the hull, and is in fact the recommended method.

[@rickkwitkoski1976]

Thanks

[@bullhippo9023]

The last thing you want is that huge seacock supported by the thru Hull fitting. Good way to sink your boat !

[@SailingSunday]

We chose these as we haven’t heard of a Tru-design fitting snapping and sinking a boat before, but regularly hear of metal thru hulls snapping due to corrosion and sinking boats...

[@PawlSpring]

After sanding to gel coat, it seems like an epoxy barrier coat should be applied before the through-hull is installed.

[@SailingSunday]

I wanted them all sealed straight onto the gelcoat then I went over them with the barrier, primer and antifoul. I think either way is going to be fine, as I said in the video don't stress as long as everything is sealed you'll be safe.

[@tonystlove]

Great Video! Simple and well put together, I was wondering if you had to do any of them with a 90degrees elbow before the seacock? I’m not as fortunate in terms of height in my bilges and most of them are 90degrees then the seacock. Any of yours needed to be like that? Thanks

[@SailingSunday]

Thank you. I didn't in the end, I guess you just can't use the collar if using an elbow first. Everything always has its sacrifices though! To me, I would probably rather use composite seacocks though with an elbow still. The only thing you would need to worry about is having something heavy stored against it, but you shouldn't have anything stored against it anyway, metal or composite.

[@romulovinhas5725]

Did you use the trudesign spanner to connect the ball valve to the skin fitting?

[@SailingSunday]

I didn’t, it would have definitely come in handy though. I used one of those key spammers from the grinder and it fit well. My partner Brittni was under the boat holding it while I was inside tightening it. If you had the trudesign spanner you could do it yourself.

[@marcvandermeulen1807]

Great video! I am wondering: I sanded down through the gelcoat to the point you can actually see the GRP coming through. Would that be a problem, using Sikaflex 291i? Thanks for your answer!

[@SailingSunday]

I would put gel coat back over it and sand it smooth again before installing the thruhull. Silicone is obviously waterproof but you want to protect your fibreglass from water at all costs.

[@marcvandermeulen1807]

@@SailingSunday thanks for your advice. Would a thin coat of epoxy do the job as well?

[@sailingvesselblacklotus1695]

I need to replace my seacocks and through-hull fittings, I'm considering Trudesign. In the video, it looked like you went with Domed fittings instead of Recessed, why Domed over Recessed?

[@SailingSunday]

I used domed fittings because it was a quick simple straight swap over. Recessed would be much better, especially for racing, but I would have needed to do more prep work and parts of our hull are quite thin so to recess the other fittings in would have required more work on the inside and need a backing plate against the hull etc. If I had the tools and more time, the recessed fittings would have been awesome to use!

[@changodelaporcelainacanada4819]

Thx. On my Beneteau , there appear to be metal washers between the skin fitting nut and the hull skin. I noticed Trudesigm has a composite skim fitting washer,,, did you reuse the original skin fitting metal washer along with tru design washer?

[@SailingSunday]

No, I used the Nylon ones from Tru-Design. The fiberglass is so thick, the washer will be the last thing that fails but if your hull is thin in any areas, you can cut something larger to spread the load further, but would still need a washer of some sort for tightening the nut onto.

[@changodelaporcelainacanada4819]

Sailing Sunday thx for the tips.

[@yaa63]

PROOOOOOOOOOO🤙🤙🤙🤙

[@SailingSunday]

Thanks!

[@DiscoSteX]

Do you need the load bearing part over it?

[@SailingSunday]

The load bearing part is to comply with the North American ABYC H-27 standards. The 2" skin fitting complies without the need for the collar. We didn't need it but we used it anyway.

[@stevenmarrone1526]

Do you paint around it after it’s dry?

[@SailingSunday]

Yes, I paint around it and inside them

[@estrelladelmar6466]

How often should a thu hull be changed?

[@SailingSunday]

There's honestly no real answer to that, many people had told me if they are pink colored, they need to be replaced. But, I had some that looked terrible, appeared to be full of galvanic corrosion and pink but they weren't actually that bad. I did however remove one that appeared to be in good condition compared to the rest, and it crumbled in my hand as I pulled it out... You can see that one in the video! As a guide though, these were 10yrs old from factory when the boat was built, and some were only 1mm thick around the rim and others were about 3mm thick. For me, everyone gave me different advice about how bad mine were that it was stressful which is why I chose these ones. I expect that I won't ever have to worry about them ever again now.

[@sadidiker]

🖒🖒🙌🙌

[@waterboy8999]

Are there any non music videos on this subject?

[@Realcjs]

Just watched a video of a boat almost sunk because they use nylon

[@SailingSunday]

If it’s the same one I saw, it ended up being the speed and depth sensors.

[@borys2767]

Would have been a better video if film speed was normal.

[@SailingSunday]

There's many great videos on KZbin installing these so we tried to keep this simple, quick but still informative. I actually kept one thru-hull original and have a Tru-Design thru hull fitting spare, so when we lift out again we will do another video and go into greater detail replacing it.

[@jimgalligan50]

Never use plastic

[@Toob41]

It's not plastic it's a glass-reinforced nylon composite and is ABYC approved and doesn't suffer from dezincification, electrolysis or corrosion. I bet your boat's made of plastic!