Advice on These Thru Hulls From Raymarine

[Madehn]

Thanks for the thoughts from everyone- i have decided to go conservative and put in bronze thru hulls for both sensing units- may not be necessary but i will sleep better with them and that is more important to me than the cost of the new units. thanks again- i may be overthinking/overbuilding it but oh well....

[Icarus]

Originally Posted by Madehn

thanks all for the quick replies- yes i do have a plastic boat BUT 1 1/2 fiberglass is a little different from the cheesy sides of these thru hulls not to mention the plastic nut on top of them- -- good to hear that they have bronze housing transducers- i sassume that they make those because there is a need for something sturdier / longer lasting than the plastic ones-- or maybe there is just a market for paranoid types that worry about the plastic ones as for what i have right now, the boat's depth was from a transducer mounted on the inside that shot through the hull without a thru hull fitting- did not have any speed other than GPS. Thanks again all for your replies- am reaching out to airmar and to the vendor that i bought the units from.

I guess the cost comes into it..
I have a 25 year old plastic, retractable paddle wheel log, still working fine.
Years ago, when one bought a new depth sounder a bronze transducer was included, these days one has to buy the transducer separately.

[Icarus]

Originally Posted by Madehn

After reading some of the replies, i thought perhaps i was being a bit paranoid and did some more research-- what i found at practical sailor tells me that my instinct that these nylon thru hulls are NOT a good idea for this type of below water line sensor. I have since gone back and ordered new thru hulls (bronze) made for the RayMarine i50/i60 setup. Here is the article from practical sailor:

https://www.practical-sailor.com/sys...h-hull-warning



No disrespect for those that feel they are strong enough-- your boat your choice but i think i am going to go with practical sailors advice and my gut.

Through hull depth sounder/log fittings are not made of Nylon.
They are talking about skin fittings which might brake down getting exposed to UV.
Anyway, you got your bronze through hull...

[noelex 77]

Originally Posted by Icarus

I guess the cost comes into it..
I have a 25 year old plastic, retractable paddle wheel log, still working fine.

The concern about plastic depth and speed transducers is not about their long term durability (which is excellent) but rather about their strength.

Most boats do not tolerate plastic skin fittings below the waterline. Some boats use Marelon which is a form of glass reinforced plastic, but this material is stronger and less brittle than the plastic typically used for the transducers.

Strangely the concern about using ordinary plastic skin fittings below the waterline is ignored for transducers.

To compound the problem, many boats have their transducers mounted on the very bottom of the boat in front of keel and near the bow. This is the slamming area. Many dedicated long distance cruising boats incorporate reinforcement in this area, such as layers of Kevlar, because if you’re unlucky enough to hit some debris, particularly as the boat comes off a wave, this is the hull area that is most likely to be damaged.

The risk is not high, but it is not a concern that should be dismissed completely, especially if the problem can be eliminated by steps such mounting the transducers at the bottom of a waterproof locker. I have only met one long distance cruising boat that suffered severe water ingress from a broken transducer fitting, but this is still one too many.

[goboatingnow]

Originally Posted by Trawlerman

As I have previously commented in other topics, I really wonder why anyone in this day and age would want a water-speed sensor. GPS is so accurate these days and has the advantage of true speed-made-good over distance, which for planning time-to-go to destination is a must have. On the inland rivers that I boat on a lot, you could quite easily be reading a speed of 4 knots water speed and in fact be backing up! I too am a bit paranoid about having any holes in the hull that I don't strictly need, and on solid fiberglass hulls like my 50' Marine Trader the shoot-through-the-glass transducers do a fine job for depth.

Well let the argument about true wind calculation and tacking angles begin

[Jubilee39]

I used bronze thru hulls when I built the boat. Fiberglass boat metal thru hulls. However when I started working with metal boats I found that the thru hulls were plastic, go figure. The plastic (marelon) are reliable and don't sieze up as readily as the metal ones. The plastic autohelm depth transducer has been in place for 30 years. Works with the Raymarine instruments.

[noelex 77]

Originally Posted by Jubilee39

However when I started working with metal boats I found that the thru hulls were plastic, go figure.

This is to eliminate the potential for dissimilar metal corrosion.

Many metal boats use Marelon seacocks but place them all above the waterline using standpipes or sea-chests. Unfortunately it is not possible to take advantage of this added security with transducers as they need to be placed below the waterline. To eliminate this issue they are frequently mounted in a watertight location so flooding will not cause damage. Some metal boats also weld small half circle fins to the side of the transducers minimising the chance of debris striking the transducer.

[smacksman]

Originally Posted by RedneckRedcoat

I couldn’t resist with that one . Figuring out where your at with a compass and a map is something everyone should learn. I personally would only call mayday if our boat was actually sinking.

But then you need electricity to call 'Mayday' Seriously though, we rely too much on electricity afloat and it is notoriously at odds with salt water.


Just before we left Cape Town making towards St. Helena the gps signal frequently dropped out. This caused almost panic amongst the cruisers and kept them harbour bound. We set off with sextant, a good watch, paper charts and tables.
I know you all laugh at me and I can take a joke, but sh*t has happened to me many times and a backup is good to have.

[goboatingnow]

Originally Posted by smacksman

But then you need electricity to call 'Mayday' Seriously though, we rely too much on electricity afloat and it is notoriously at odds with salt water.


Just before we left Cape Town making towards St. Helena the gps signal frequently dropped out. This caused almost panic amongst the cruisers and kept them harbour bound. We set off with sextant, a good watch, paper charts and tables.
I know you all laugh at me and I can take a joke, but sh*t has happened to me many times and a backup is good to have.

I like electrons. Never leave harbour without some nice ones aboard. More and more these days good job they are small

[Rothblum]

Originally Posted by Madehn

... what i found at practical sailor tells me that my instinct that these nylon thru hulls are NOT a good idea for this type of below water line sensor. .... i think i am going to go with practical sailors advice and my gut.

The Practical Sailor article did not really nix "plastic" thru-hull fittings. It nixed NYLON thru-hulls for the contradictory reason that they are susceptible to UV, so were not suitable for UNDERWATER locations. The fact is that water reflects most UV, the thru-hulls are mostly in the shadow of the hull, and the remainder is at least partly absorbed, so the ostensible reason for the PS recommendation is not valid.

Practical Sailor added that "Nylon should not be confused with Marelon a high strength, polymer composite, developed as a solution to electrolysis and corrosion problems associated with bronze/brass plumbing fittings. It is UL/ABYC approved and ISO certified for use below and above waterline."

So, it seems you are not going with Practical Sailor's advice.

[noelex 77]

Originally Posted by Rothblum

Practical Sailor added that "Nylon should not be confused with Marelon a high strength, polymer composite, developed as a solution to electrolysis and corrosion problems associated with bronze/brass plumbing fittings. It is UL/ABYC approved and ISO certified for use below and above waterline."

I don’t think the transducer housings are Marelon, they certainly don't look and feel like Marelon. I suspect they are a type of ABS plastic. Does anyone know for sure?

[HeywoodJ]

Originally Posted by noelex 77

I don’t think the transducer housings are Marelon, they certainly don't look and feel like Marelon. I suspect they are a type of ABS plastic. Does anyone know for sure?

Does it really matter if the units meet the definitions in ABYC H-27/UL 1121/ISO 9093-2? Or are we second-guessing the engineers who design to those standards and the people who put together the standards in the first place (not that I necessarily think we shouldn't second-guess standards)?

[Cwens]

Originally Posted by Madehn

After reading some of the replies, i thought perhaps i was being a bit paranoid and did some more research-- what i found at practical sailor tells me that my instinct that these nylon thru hulls are NOT a good idea for this type of below water line sensor. I have since gone back and ordered new thru hulls (bronze) made for the RayMarine i50/i60 setup. Here is the article from practical sailor:
https://www.practical-sailor.com/sys...h-hull-warning

No disrespect for those that feel they are strong enough-- your boat your choice but i think i am going to go with practical sailors advice and my gut.

The Practical Sailor article shows a picture of what looks to me like a proper bronze Groco through-hull, with the caption "Nylon thru-hull fittings like this are culprits in more than a few sinkings" What's up with that?

[noelex 77]

Originally Posted by HeywoodJ

Does it really matter if the units meet the definitions in ABYC H-27/UL 1121/ISO 9093-2?

Absolutely. It is surprising the number of boat owners that have no idea of the methods and materials that go into their vessel’s construction and its important components.

I was a technical advisor on a standards committee (not marine related) for several decades and my recommendation would be not to rely on standards alone to determine the safety and suitability of products.

Some of the marine standards are particularly woeful . The CE Recreational Craft Directive Cat A standard and the standard classifying anchors are two examples.

The ABYC writes better standards than most, but I note that it does not test or even make recommendations on the impact strength when subject to external forces such as when hit by floating debris. The risk is not great, but I think this is the greatest weakness with plastic transducers. I suspect if this requirement had been included manufacturers would have used the more expensive Marlon for their transducer housing construction.

Fortunately, there are simple steps that can be taken to reduce or even eliminate any risks and I think these measures are worth considering for offshore cruising boats.

Originally Posted by HeywoodJ

not that I necessarily think we shouldn't second-guess standards

Nice to see that you have some healthy scepticism .

[Jubilee39]

Originally Posted by noelex 77

This is to eliminate the potential for dissimilar metal corrosion.

Many metal boats use Marelon seacocks but place them all above the waterline using standpipes or sea-chests. Unfortunately it is not possible to take advantage of this added security with transducers as they need to be placed below the waterline. To eliminate this issue they are frequently mounted in a watertight location so flooding will not cause damage. Some metal boats also weld small half circle fins to the side of the transducers minimising the chance of debris striking the transducer.

You missed the point completely, If plastic thru hulls are good enough for metal boats why would one want to go to the expense of metal thru hulls. I personally have installed many thru hulls on metal boats. There might be a nipple welded on the hull and the plastic fitting screwed on to it. rarely would you place the actual valve above the waterline, where is the waterline when the boat heels.