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thru hull failure

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thru hull failure

Postby 1st Sail » Mon Mar 12, 2018 2:06 pm

I recall last fall reading a post referencing ABYC finding regarding plastic thru hull failures. Received this in my email from Practical Sailor. C:\Users\Dave\AppData\Local\Microsoft\Windows\INetCache\Content.Outlook\JVUMRKU3\email.mht
Any comments on the long term durability and reliability of the the OEM 26M thru hull? Time to upgrade?
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Re: thru hull failure

Postby paul I » Mon Mar 12, 2018 3:55 pm

1st Sail wrote:I recall last fall reading a post referencing ABYC finding regarding plastic thru hull failures. Received this in my email from Practical Sailor. C:\Users\Dave\AppData\Local\Microsoft\Windows\INetCache\Content.Outlook\JVUMRKU3\email.mht
Any comments on the long term durability and reliability of the the OEM 26M thru hull? Time to upgrade?


That link just isn't telling anyone anything. It looks like a location on your local drive.

I own an :macx: . Its OEM "thru-hulls" are molded into the hull. All of them are above the water line.

Are the :macm: OEM thru-hulls similar ?
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Re: thru hull failure

Postby RussMT » Mon Mar 12, 2018 4:20 pm

I think you are referring to this article

https://www.practical-sailor.com/issues ... 215-1.html

The M has one thru hull fitting for the sink/motor well drain. It is normally above the water line. However, my boat is aft heavy and this is often below water.

I wouldn't be concerned with it. However, INSIDE the boat are hoses that should be inspected. Particularly the T fitting between the motor well drain and sink. To be honest, I've never inspected mine, but I should. Maybe even double hose clamp it if possible. Good reminder.

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Re: thru hull failure

Postby kurz » Mon Mar 12, 2018 4:38 pm

the through hull of my :macm: is all time below water line. Especially like now in winter when the ballast ist empty... would be nice to get it above water line. Do not see how bewouse of the drain of the motor well...
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Re: thru hull failure

Postby Tomfoolery » Tue Mar 13, 2018 9:34 am

The only white nylon thru-hull I have is the holding tank (as it were*) vent, and that's up near the rub rail. If that thing breaks, the odor will give me a clue, assuming it was used, which it rarely is. If water is coming in, I've got much bigger problems than a little thru-hull failure. :wink:

*MSD version of a porta-potti
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Re: thru hull failure

Postby kurz » Tue Mar 13, 2018 10:02 am

How the :macx: empies the motor well? Is it so high that is above the waterline?
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Re: thru hull failure

Postby paul I » Tue Mar 13, 2018 10:29 am

kurz wrote:How the :macx: empies the motor well? Is it so high that is above the waterline?


On mine yes... it is barely above the water line. It may drop below the water line when the boat is being motored and on a plane. I'll have to take a look.
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Re: thru hull failure

Postby Tomfoolery » Tue Mar 13, 2018 10:32 am

It is above the water line, but not by a lot. I don't have any boat pictures on this computer, but it's like 5 cm above the water line, and dips below in any kind of bobbing, or with a couple of lard-oes* at the stern. Like me. :|

It's a molded-in pipe, with hoses and pvc or nylon ell fittings. Kinda cheesy, but has worked since the boat was built, so there's that. But if it failed, it would eventually take on enough water to start the death spiral by putting the fitting below the water line.

[*Schmalz Arsch, glaube ich.]
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Re: thru hull failure

Postby Starscream » Tue Mar 13, 2018 10:58 am

kurz wrote:How the :macx: empies the motor well? Is it so high that is above the waterline?


The exit of the motor well drain is above the waterline if the boat is floating empty. While swimming off the back of the boat with friends I've seen water coming into the motor well from the drain hole. It goes that far underwater with weight on the back and/or waves.
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Re: thru hull failure

Postby paul I » Tue Mar 13, 2018 12:32 pm

Tomfoolery wrote:It's a molded-in pipe, with hoses and pvc or nylon ell fittings. Kinda cheesy, but has worked since the boat was built, so there's that. But if it failed, it would eventually take on enough water to start the death spiral by putting the fitting below the water line.


I agree with all that. The really scary thing is that if it did fail you really wouldn't know until it became a pretty serious problem. The incoming water would just fill the bilge area under the rear berth until it got high enough to overflow out of the little weep hole drilled into the fiberglass under the companionway ladder. I'm only guessing, but I'll bet it could take on perhaps 100-150 gallons before it was caught. You'd have this same problem regardless if it were an actual thru-hull or the molded pipe design.

On the other hand, even though the assembly looks cheesy, it does have its advantages. Because its molded, there is nothing protruding from the hull at all. No fitting to hit or break from the outside. The connections between the motor well and drain aren't under any real pressure, so you would think any problem would start as a small drip before it got big enough to cause a real problem. To damage it you'd be damaging the hull itself... in which case there would be bigger problems to contend with.

The thing I found kind of odd is the molded in pipes aren't even barbed. The vinyl tubing looks like it was heat shrunk onto them. Its easy enough to do... microwave up a cup of water... soak the end of the plastic tube in it for 30 seconds or so... then slide it onto the pipe. The diameter of the tube will stretch like putty and get very tight once it cools. The hose clamp is probably a formality. But I'd still feel better if the thru-hull pipe had barbed ends.

Probably the most common thing to go wrong would be the vinyl tubing getting brittle and cracking enough to permit a slow leak.
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Re: thru hull failure

Postby Tomfoolery » Tue Mar 13, 2018 2:01 pm

kurz wrote:How the :macx: empies the motor well? Is it so high that is above the waterline?

I found one of my own pictures using google. It shows the engine well drain hole, visible in the middle of the boarding ladder, and right at the bottom paint line. The water line is where the slime line is; the PO had bottom painted up to the boot stripe. But you can clearly see the hole, which I circled in red.

Image

I couldn't find the one behind the stern berth panel showing the hose and connections, but at least the one above gives you an idea how close the thru-hull is to the waterline.

And look how much it lists, based on the slime line to boot stripe line; it was probably taken before I moved some heavy things around. That, or the PO painted the bottom crooked. :|
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Re: thru hull failure

Postby 1st Sail » Tue Mar 13, 2018 8:56 pm

My bad. I posted in a rush and did not proof the link. I tried to find the ABYC article from last fall no luck so far. IIRC the article specifically referred to plastic thru hulls. However, there are different qualities of plastic thru hulls as reference in the post narrative. With due respect to MacGregor's safety record I am inclined to think our present thru hulls are reliable.

https://www.practical-sailor.com/issues ... bbag031118

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Re: thru hull failure

Postby sailboatmike » Wed Mar 14, 2018 4:17 am

Mine is a very early (1995) X, My ballast inlet in on the starboard side and motor well drain on the port side. Wonder what year they switched it all around
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Re: thru hull failure

Postby 1st Sail » Wed Mar 14, 2018 9:32 am

SailboatMike,
Not to hijack my own thread,But .... your motor mounted tail lights makes a lot of sense. I'm going to build a light bar to add for long trips on the interstate. I would not want to defend myself over the distance from the rudders/OB lower unit to trailer tail lights if I was rear ended. Considering the average IQ of the drivers today the light bar is a good defense when you can't fix stupid.
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Re: thru hull failure

Postby BOAT » Wed Mar 14, 2018 9:52 am

The M boat has a plastic thru hull that is just slightly above the water line.

I do not know what article your reading but the sad truth is that plastic thru hulls do indeed fail more than metal ones because of cracking, expansion, and even worse: CONtraction - when the plastic shrinks and becomes porous due to cold weather or sun exposure the flange pulls away from the hull and the seal becomes compromised and then the leaks start and the sea comes into your boat. The plastic fittings are fine when they are well above the water line like the thru hull on the M boat in the bow where the anchor locker drains but the thru hull in the transom is not (in my opinion) a 20 year fitting. The factory attaches the hoses on my boat with stainless clamps and a barbed T and lots of sealant but really it is on my list to replace that whole assembly with a valve and new hose this winter - I was planning on replacing that very set up this April.

I don't think it will sink the boat but think of what a hassle it would be to be out in some primitive Island bay like Isthmus or Whimby Island and have that stupid thing start leaking just because you and the Mrs bed down at night in the aft bunk and (if your old like us) you carry a lot of ballast in your butt and make the aft section dip down into the water - talk about a lousy night on the boat. "Oh gee! or butts are so big we are taking on water when we lay down in the aft bunk!"

I don't think the wife is going to like that 'ass'esment of the situation at 11PM after a night of grog.
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