Thru Hull Below The Water Line

[stollo770]

Hello,

I am planning on installing a new thru hull beneath the water line of my boat. The thru hull is an inch in diameter and is made of plastic because I dont want to worry about corrosion. I know how to seal it and stuff, I've done thru hulls above the waterline before, but this is my first time doing one under the waterline. My main question is what to do about the paint. I'm pretty sure I can't put the thru hull on my ablative paint because its designed to wear with time, and I'm not sure if it can go on the barrier coat. So what do I seal the thru hull to? Do I need to sand down to get underneath everything, or can the thru hull be sealed to a painted surface? Any help would be appreciated.

Thanks for your time,

 

[Canyonkeeper]

Stollo. I cannot speak for plastic thru hulls but I can speak for about 100+ plastic transducers I have installed. They can be painted just the same as everything else. It will wear the same as the rest of the bottom.

What is the intake for BTW?

 

[stollo770]

Thanks Canyon keeper. I wasn't sure how the painted surface would take the thru-hull sitting on it on but I guess if it works for transducers then I can't see why it wouldn't work for thru-hulls. The intake is for a marine a/c unit that I just got, it needs water for its heat exchanger. I used to have a portable a/c unit that I mounted in my companion way but hauling it around on trips was annoying. The shipboard a/c is compact and will live permanently inside my port side settee which will eliminate lugging around my old, heavy portable a/c unit. I realize that it is the middle of winter right now, but I got the unit for a good deal and I figure the sooner I get it in, the less work I'll have in the spring.

 

[kito]

Do yourself a favor and get a bronze thru hull fitting.....especially below waterline. I would never install plastic fittings below waterline. Spend a few extra bucks and do it right.

 

[sailor832]

when you say plastic be careful what type there are plastic thru hulls for above the waterline the ones for below are usually glass reinforced type One is Marelon® plumbing systems to the world’s top boat builders and continues to develop modern alternatives to age old heavy bronze fittings. We are the only manufacturer to offer motorized Marelon® seacocks (ROV systems) that meet and exceed all Marine U.L., ABYC and ISO standards

 

[stollo770]

Thanks for the added info. I'll look around for some better thru-hulls besides the cheap plastic one I got from Westmarine. I would hate to have to repeat this job in the future, drilling through my hull once is stressful enough.

 

[Ed Schenck]

On Ladylove I put a T-valve on top of the engine water seacock. Since I can't run the A/C and the engine at the same time this works for me. Hose to left goes to engine and to right the A/C filter then pump.

 

[Benny17441]

Rule #1, do not use plastic thru-hulls under the water line. They are OK for anchor locker, sink and cockpit drain discharges above the water line but are not safe for use below.

 

[Dalliance]

If I understand your primary question,....you can not seal anything to ablative paint. You need to sand it down to the epoxy barrier coat. As for plastic thru-hull fittings below the waterline.... As the others said, if it's not Marelon, no no no.

 

[kito]

I bet the price difference between marelon and bronze is not that much. What kind of seacock are you going to use? It's best to use a bronze thru hull screwed into a bronze seacock imo. I just removed all my 36 year old bronze thru hulls and they were in great condition. Only reason why I didn't reuse them is because of the crappy gate valves Hunter installed....had to cut them off.

 

[stollo770]

If I understand your primary question,....you can not seal anything to ablative paint. You need to sand it down to the epoxy barrier coat. As for plastic thru-hull fittings below the waterline.... As the others said, if it's not Marelon, no no no.

You do understand my question. Thank you very much for your answer, I was under the impression I would have to sand everything off. I'll just stop at the barrier coat and seal the thru hull to that.

 

[stollo770]

I bet the price difference between marelon and bronze is not that much. What kind of seacock are you going to use? It's best to use a bronze thru hull screwed into a bronze seacock imo. I just removed all my 36 year old bronze thru hulls and they were in great condition. Only reason why I didn't reuse them is because of the crappy gate valves Hunter installed....had to cut them off.

I was going to use a bronze thru hull. I guess I'll take your advice and go bronze to bronze. I just want whatever will last the longest and won't disintegrate on me while I'm underway. Thanks for the info kito.

Also, Ed, thanks for the info about splitting the sea-cock to go to the a/c. I won't be running my engine and a/c at the same time either but I don't want to merge their plumbing because it adds too many worries for me. If something happens on the a/c side then I'll blow out my impeller and cook my engine, and if something happens on the engine side then I'll probably ruin the a/c unit. I'm sure it works fine for you but I worry to much for things like that, plus my engine has been through enough.

 

[pvtpotter]

stollo770.
I have an H27 and I would love to see your A/C install. Can you get any pics of where you installed, how you ran the ducting, electrical panel, etc. It would really help me figure out the feasibility of the install.
Thanks.

BTW, Marelon is find under the waterline, never use nylon, as you are aware. I have never been a fan of marelon on bronze. Metal on "plastic" never good. They make Marelon through hulls too. You could go marelon on marelon.

Thanks for reading. Would love to see some pics.
Cheers.

 

[stollo770]

Thanks for the interest pvtpotter. Right now the A/C is not installed yet, but it will be in a couple of weeks once the temperature in NJ warms up enough for PL5200 to cure. I'll be glad to post some photos then.

As for my design, I am planning to install the unit in the forward end of my port settee. its compact enough to fit, and I chose that location because I have lots of free space there. All I need to do is build a small shelf to level it and it'll be fine. I plan to run the ducting, right out the side of the settee to a vent that diverts the air to all different directions. The unit comes with a little thermostat, which I plan to install next to my main electrical panel. I also plan to install another small electrical panel somewhere around my main panel for the AC unit. The AC unit panel will have a breaker switch for DC, a breaker switch for A/C, and an indicator light. Wiring from the panel will go direct to the batteries/main A/C switch. I chose to install a complete panel because its got all the fuse protection stuff that I'll need for a unit like this. As for the water supply, I plan to have two thru hulls, one for intake and one for exhaust both below the water line. I was tempted to run the exhaust water out the bilge line but I didn't want to be listening to water falling over the boat every time my AC was on. Plus it would have looked like my bilge was flooding. The condensation from the pan of the AC unit will simply be routed via a small hose into the bilge.

It may sound a bit confusing from how I worded everything, but the install is pretty straight forward. I'll post the pics when I finish it.

 

[pvtpotter]

Stollo770,
That sounds great. I was contemplating doing it aft in the starboard settee. I don't use my through hulls for the head (I'm installing a self-contained SeaLand unit with fresh water and an integrated holding tank. I thought I could tap off the old head through hulls. I have never seen a configuration where the exhaust AC water goes overboard under the waterline. I wonder about back wash, but if you can close the seacock I don't see a problem with that. Except maybe back pressure from the boat sitting in the water. You could always send the exhaust to your head sink. That is an above the waterline thru-hull which isn't used very much.
You condensation drain sound perfect. I wonder, what brand name are you going with? I know there are ultra compact units available. Expensive, expensive. This summer I'm going to tackle refrigeration and maybe hot water. I'm keeping to the silly household A/C unit in the companionway. Maybe next year.
Also, in terms of the A/C 120V panel, I bought a new one with a Volt meter and 3 integrated switches. The old singular breaker on the DC panel bit the dust so I decided to go with a completely new panel. Now I just need to figure where to mount it. I'm thinking of making a mounting board above the navigation table.
Keep us up to date. We would love to see the pics. I have not seen any A/C units installed on a H27.
Thanks!