Through hull fittings on Aluminium sailboat

[Fore and Aft]

Manateeman I am fairly certain plastic seacocks are not that bad. I am talking proper seacocks not those white plastic ones with a hose barb on the end. The only good thing about them is that they are easy to snap of once the sun has made them brittle enough.
I must survey at least a 1000 seacocks and skin fittings a year and cannot remember any issues with the plastic ones? Maybe your experience has been different?
Cheers

[DeValency]

Originally Posted by Manateeman

Professional boatbuilders do not often detail mistakes they have made especially when it is on their own yacht after a history of building for over half a century.
The worse mistake I made was installing Forespar Marelon seacocks.
Under no circumstances would I use Trudesign. It is a supported thru hull attached to a ball valve and in my opinion, not a true seacock.
Standpipes with support is an excellent option but is simply very difficult to weld in some locations.
When I finish removing all the plastic I will use Groco stainless adaptor plates and Groco thru hulls without the nuts. The Groco adaptors will be attached to pre threaded backing plates welded to the hull with insulation between the welded plate and the adaptor. Ted-Gel on the bolts. You can use Groco 316 stainless ball valves or other commercial valves.
I had the hot side interior of my turbo coatedwith CeraKote and might do the Grocos as well.
There is a web page on marinehowto ? (Maybe someone can help here) with nice photos. One could use Marelon thru hulls ( no nuts) which might save time.
With the Groco adaptor, failure of the thru hull from the hull exterior, is not going to sink you because the adaptor is secured to the hull. It’s a seacock, not a supported ball valve. You can buy three part ball valves and TIG one part to the Groco adaptor plate...an expensive option. We wanted flush thru hulls so we beveled the hull and TIG welded the edge, and the backing plate. Looks beautiful, super strong but takes careful TIG work.
Now we will hear from all the “experts” about how plastic is good. You can review my credentials and decide for yourself. Till then,
Happy trails to you
Captain Mark and his “drink more beer, make more aluminum boats” manatee crew.

Sounds like a perfect retirement fund plan for a boatyard service provider. With my 15 through hull fittings I can see at least a month of work...

TruDesign has also a recessed through hull fitting - not only the common mushroom, so the likelihood of being shaved is minimal.

Also, I have glued-sealed the skin fitting with 5200 from the inside and as much as possible around the fitting thread. Even if the mushroom will be shaved, the fitting will stay sealed in place.

[Fuss]

Originally Posted by Manateeman

Professional boatbuilders do not often detail mistakes they have made especially when it is on their own yacht after a history of building for over half a century.
The worse mistake I made was installing Forespar Marelon seacocks.
Under no circumstances would I use Trudesign. It is a supported thru hull attached to a ball valve and in my opinion, not a true seacock.
Standpipes with support is an excellent option but is simply very difficult to weld in some locations.
When I finish removing all the plastic I will use Groco stainless adaptor plates and Groco thru hulls without the nuts. The Groco adaptors will be attached to pre threaded backing plates welded to the hull with insulation between the welded plate and the adaptor. Ted-Gel on the bolts. You can use Groco 316 stainless ball valves or other commercial valves.
I had the hot side interior of my turbo coatedwith CeraKote and might do the Grocos as well.
There is a web page on marinehowto ? (Maybe someone can help here) with nice photos. One could use Marelon thru hulls ( no nuts) which might save time.
With the Groco adaptor, failure of the thru hull from the hull exterior, is not going to sink you because the adaptor is secured to the hull. It’s a seacock, not a supported ball valve. You can buy three part ball valves and TIG one part to the Groco adaptor plate...an expensive option. We wanted flush thru hulls so we beveled the hull and TIG welded the edge, and the backing plate. Looks beautiful, super strong but takes careful TIG work.
Now we will hear from all the “experts” about how plastic is good. You can review my credentials and decide for yourself. Till then,
Happy trails to you
Captain Mark and his “drink more beer, make more aluminum boats” manatee crew.

I absolutely agree with you ... for an expedition boat, but thats not what we are talking here, we are talking normal boats and for normal boats trudesign is fine.
No expedition boat would have 6mm aluminium under the water like the OP has and so trudesign is fine in this case.

[Michael Cobbe]

Our steel boat had Marelon throughulls, which are plastic, they were fitted by the previous owner who was a shipright.

[stormalong]

My boat has 13 Marelon seacocks and through hulls. About half of them are original to the boat (1985), the rest were either added or replaced by me. I have never had a dangerous failure. Some would not close so they were replaced. I have replaced a few of the original through hulls due to changes in seacock sizes. I tested the removed through hulls with a hammer. None cracked and they all took quite a beating before I gave up.

I know that the early design of Marelon seacocks had a tendency for their handles break off. Forespar admitted this to their customers decades ago and redesigned them. I have not seen a handle break off.

How many bronze seacocks have lasted 35 years?

Manateeman, I would like to know what has made you so down on Marelon and how long ago you came to your conclusion?

[double u]

...yeah, stainless stuff on through-hulls & ball valves...just a few additional little wires & some LEDs & - voila, nightlights for the boat...!

[Manateeman]

OK...fair question. Why do I detest Forespar Marelon. Same reason I detest Bomar Ocean hatches. The companies sold dangerous products and to add insult to injury, failed to notify anyone and failed to make good on the defect.
Forespar knew they made a mistake. Valves stuck open, handles broke off.
That’s just fact not my opinion. We spent a lot of time on the internal backing plates and the welding. When we found out about the defective design, they told me to stuff it. Same with Bomar after the lense broke from stepping on it.
Tru designs are supported ball valves and are cheep and fast to put in. That’s the pitch to boatbuilders at IBEX. The valve is not attached to the hull. Boston racer uses 5200. What? Not even Plexus? Honestly, if you want to go cheap, you look at seacocks? By the way, I built a boat more than 35 years ago and all her Apollo seacocks work fine as the day I built her.
The question is simple. WHY put in plastic when Groco offers a ballistic system.
It’s solid and you can change the valve. Plastic is just about saving money .
Let the owner decide. All I did was offer my experience.
I get “peanut gallery” comments like the electric boat baloney. Now it seems people who don’t even own a boat can comment on how I build. Or “ we don’t like you manatee” ...Sixty years building and I’ve seen price and not quality, produce thousands of shoddily built boats. They ruin dreams and bodies. But Ken, Barbie and the cat prove otherwise.
Happy trails to you
Captain Mark and his electric bilge water manatee crew

[Fuss]

Originally Posted by Manateeman

OK...fair question. Why do I detest Forespar Marelon. Same reason I detest Bomar Ocean hatches. The companies sold dangerous products and to add insult to injury, failed to notify anyone and failed to make good on the defect.

Forespar knew they made a mistake. Valves stuck open, handles broke off.

That’s just fact not my opinion. We spent a lot of time on the internal backing plates and the welding. When we found out about the defective design, they told me to stuff it. Same with Bomar after the lense broke from stepping on it.

Tru designs are supported ball valves and are cheep and fast to put in. That’s the pitch to boatbuilders at IBEX. The valve is not attached to the hull. Boston racer uses 5200. What? Not even Plexus? Honestly, if you want to go cheap, you look at seacocks? By the way, I built a boat more than 35 years ago and all her Apollo seacocks work fine as the day I built her.

The question is simple. WHY put in plastic when Groco offers a ballistic system.

It’s solid and you can change the valve. Plastic is just about saving money .

Let the owner decide. All I did was offer my experience.

I get “peanut gallery” comments like the electric boat baloney. Now it seems people who don’t even own a boat can comment on how I build. Or “ we don’t like you manatee” ...Sixty years building and I’ve seen price and not quality, produce thousands of shoddily built boats. They ruin dreams and bodies. But Ken, Barbie and the cat prove otherwise.

Happy trails to you

Captain Mark and his electric bilge water manatee crew

As I said... for an expedition boat ok, but thats not what we are talking here, we are talking normal boats and for normal boats trudesign is fine.
No expedition boat would have 6mm aluminium under the water like the OP has and so trudesign is fine in this case.

It not absolutely critical that normal boats have Groco seacocks and through hulls and attach the valve to the hull.

Do that on your expedition boat, but for normal boats there are other adequate solutions like tru design.

[double u]

"...I get “peanut gallery” comments like the electric boat baloney. Now it seems people who don’t even own a boat can comment on how I build."
care to read my previous posts in this thread? 2 rtw in an aluminium boat...
& no, stainless & aluminium...no galvanic corrosion, none...!

[Fore and Aft]

Manateeman take a chill pill, there is more than one way to skin a cat and you don't need to spend thousands of dollars doing it.
Cheers

[Wideocean7]

Great debate. I should add that I do intend to venture to high latitudes. I didn’t make that clear when I originally posted, not understanding that it would make a difference I take on board comments that a 6mm aluminium hull might not be up “expedition” yacht standards, but that’s what I’ve got and can afford. (She was built in Vancouver with thicker bow plates and crash bulkhead). So I guess the question remains-are TruDesign fittings up for that or are the Groco fittings that way to go, now that I’ve said I will be venturing far north/south? For whatever reason I am very nervous about dissimilar metals, hence had been previously drawn to “plastic” fittings.

[Fore and Aft]

Wideocean7 how about a sea chest? Plenty of room to easily weld an aluminium pipe to the hull in your engine room. That would take care of the generator, toilet, main engine and maybe the watermaker?
Cheers

[Wideocean7]

Fore and Aft. What’s a sea chest? Sounds expensive when I’ll also need to patch the existing through hulls.

[Fore and Aft]

Wideocean7 could you use something like this then T all your raw water intakes of this aluminium strainer from Southern Seas marine? Someone must have done something similar before?
Cheers

[Fore and Aft]