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Hi, we recently bought a 1974 Shipman 28, and would be grateful if anyone had any advice re. the thru hulls.

Here's a pic of three of them, next to the engine. Judging by the style, they are the oldest on the boat. Despite its age, the boat is in pretty good condition. Well looked after by the two POs, and kept in fresh water in Sweden's Lake Mälaren.

The bottom thru hull in the picture is the engine water intake. The top right one is the seawater intake for the sink tap. The thru hull on the left is the sink outlet, with the cockpit drain outlet also feeding into it.

My questions are:

1) Despite the old style of the thru-hulls, they seem to be in pretty good condition - are they safe to keep?

2) The engine water intake valve opens and closes fine. I haven't fiddled with the rest yet. Is it normal practise to keep the cockpit drainage thru hull open at all times? Likewise, the sink tap inlet?

Sorry for the noob questions - first time boat owner, and don't want to scuttle her inadvertently.
 

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Terminology is incorrect.

Thru hull is a fitting which penetrates hull is usually secured with a large nut. They have thread on the inside so accept a valve. Different threads are used. Make sure your valve thread matches the thru hull's thread. These come in bronze and plastic. Bronze is preferred. Don't use brass.

A ball valve with a handle is what is used for plumbing purposes. it turns 90° to open and close. Preferred. These come in bronze, stainless steel and plastic Bronze is preferred. Don't use brass

A gate valve which is what is pictured drives a plate into the body to close it off. Not recommended

Transducers for speed, temp, depth also use thru hulls. The transducer is inserted into the thru hull and secured with a nut. These come in bronze, stainless and plastic.
 

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Discussion Starter #3
Thanks v. much for the clarification


Terminology is incorrect.

Thru hull is a fitting which penetrates hull is usually secured with a large nut. They have thread on the inside so accept a valve. Different threads are used. Make sure your valve thread matches the thru hull's thread. These come in bronze and plastic. Bronze is preferred. Don't use brass.

A ball valve with a handle is what is used for plumbing purposes. it turns 90° to open and close. Preferred. These come in bronze, stainless steel and plastic Bronze is preferred. Don't use brass

A gate valve which is what is pictured drives a plate into the body to close it off. Not recommended

Transducers for speed, temp, depth also use thru hulls. The transducer is inserted into the thru hull and secured with a nut. These come in bronze, stainless and plastic.
 

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As I was reading, before I saw the pics, I was thinking it was unlikely a pic would show whether these should be replaced. Then I noticed all the sealant on the joints and covering the backing plate of one. Seems they've been giving someone trouble, so the conclusion that they are in pretty good condition isn't quite true.

Whenever I leave the boat, I close everything non-essential thru-hull. I have to leave some open, that feed the air-conditioner, for example. But sinks and engine intakes are closed.

It's not unheard of for gate valve handles to turn, but not doing anything inside. One reason they are not preferred.
 

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As I was reading, before I saw the pics, I was thinking it was unlikely a pic would show whether these should be replaced. Then I noticed all the sealant on the joints and covering the backing plate of one. Seems they've been giving someone trouble, so the conclusion that they are in pretty good condition isn't quite true.

Whenever I leave the boat, I close everything non-essential thru-hull. I have to leave some open, that feed the air-conditioner, for example. But sinks and engine intakes are closed.

It's not unheard of for gate valve handles to turn, but not doing anything inside. One reason they are not preferred.
hmmm I close heads valves except when in use... including shower sump discharge. I leave the galley sink open and all 3 in the engine room open pretty much all the time except in water winter storage.
 

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......all 3 in the engine room open pretty much all the time except in water winter storage.
The engine intakes are the ones I consider real boat sinkers. They are typically a bit below the water line, therefore, under pressure. They're also typically bigger, so a bilge pump is less likely to keep up, like it might with a sink drain at the water line.

When I'm aboard and cruising, I'm not nearly as disciplined. I'll go ashore with most things open, but rarely gone for more than a few hours. That's enough I suppose. We have a high water bilge alarm, which would help when aboard, but not at all when away.
 

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Hi, we recently bought a 1974 Shipman 28, and would be grateful if anyone had any advice re. the thru hulls.

Here's a pic of three of them, next to the engine. Judging by the style, they are the oldest on the boat. Despite its age, the boat is in pretty good condition. Well looked after by the two POs, and kept in fresh water in Sweden's Lake Mälaren.

The bottom thru hull in the picture is the engine water intake. The top right one is the seawater intake for the sink tap. The thru hull on the left is the sink outlet, with the cockpit drain outlet also feeding into it.

My questions are:

1) Despite the old style of the thru-hulls, they seem to be in pretty good condition - are they safe to keep?

2) The engine water intake valve opens and closes fine. I haven't fiddled with the rest yet. Is it normal practise to keep the cockpit drainage thru hull open at all times? Likewise, the sink tap inlet?

Sorry for the noob questions - first time boat owner, and don't want to scuttle her inadvertently.

These are "gate valves." It appears that they have backing blocks (which is good). However, because they are gate valves, you really don't know if they work, or not, unless you test them.

If this were my boat, I would replace these valves with proper bronze ball-valve seacocks. Don't cheap out on the valve, as good ones, properly installed, should last another 45+ years.

 

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The engine intakes are the ones I consider real boat sinkers. They are typically a bit below the water line, therefore, under pressure. They're also typically bigger, so a bilge pump is less likely to keep up, like it might with a sink drain at the water line.

When I'm aboard and cruising, I'm not nearly as disciplined. I'll go ashore with most things open, but rarely gone for more than a few hours. That's enough I suppose. We have a high water bilge alarm, which would help when aboard, but not at all when away.
Well conservative is better in this case. My engine intake is 3/4" w/ 5/8" hose. The the prop shaft has 2 very small...ones. Letting go would be a shocker... a few higher output bilge pumps with some sort of alarm to send a cell txt message would be cool.
 

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Well conservative is better in this case. My engine intake is 3/4" w/ 5/8" hose. The the prop shaft has 2 very small...ones. Letting go would be a shocker... a few higher output bilge pumps with some sort of alarm to send a cell txt message would be cool.
A 3/4" hole that is 2 ft below the surface will ingress 16 gallons per minute, or 960 per hour. Most pumps are not sized to pull that off, especially after their rated ability is degraded by lift to the overboard fitting. At about 800 pounds for every 100 gallons the pump doesn't discharge, it wouldn't take long to founder.

Of course, the more likely scenario is a hose split or crack, which ingresses more slowly. Still could be too fast.

They do make boat monitoring systems that connect via cellular networks. They can monitor anything, from bilge water to battery charging to entry/exit, just like home monitoring systems. At a price. A big price.
 

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Discussion Starter #10

These are "gate valves." It appears that they have backing blocks (which is good). However, because they are gate valves, you really don't know if they work, or not, unless you test them.

If this were my boat, I would replace these valves with proper bronze ball-valve seacocks. Don't cheap out on the valve, as good ones, properly installed, should last another 45+ years.

Looks like the first project is decided... thanks
 

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Gate valves are never recommended in below water applications.

First, it is never apparent whether the valve is open or closed

Second, even if it feels like the valve is closed, a piece of debris can hold the gate open

Third, many gate valves are not intended for use in salt water and will have brass parts which will deteriorate in salt water.

These valves should be replaced with the appropriate marine valves.
 

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Looks like you got some good advice here in regards to the valves and hoses.

> Is it normal practise to keep the cockpit drainage
> thru hull open at all times?

yes, so that rain (and snow melt) can drain. I leave mine open. I occasionally work them closed and open to ensure that the operate smoothly.

> Likewise, the sink tap inlet?

No I wouldn't say so. I close mine anytime I leave the boat for more than a day or so. I close all of the seacocks in the boat when I leave ...except for the cockpit drains.

I want to congratulate you on your boat! A Shipman 28 was my first keelboat many years ago. A sweet sailing boat, quite fast and lovely. I wish you many happy voyages.
 

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Andy,
You appear to have older style globe valves in lieu of the more preferred 1/4-turn ball valves.

However, your valves appear to have flanged mounting bases that a thru hull valve should have to provide shear strength that prevents breaking them off. There may even be a backing plate below your flanges, but the paint and lighting makes it hard to see.

In short, globe valves are not as reliable as ball valves. Consider your old facet handles and water spigots around the house. You need to replace the washers when they leak.

If yours do not leak and they shut off, they appear to be mounted OK. But, as I have done on my boats, I would replace them as you can with thru hull 1/4 turn ball valves as backing plates. It is not a difficult job.
 

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Discussion Starter #15
Looks like you got some good advice here in regards to the valves and hoses.

> Is it normal practise to keep the cockpit drainage
> thru hull open at all times?

yes, so that rain (and snow melt) can drain. I leave mine open. I occasionally work them closed and open to ensure that the operate smoothly.

> Likewise, the sink tap inlet?

No I wouldn't say so. I close mine anytime I leave the boat for more than a day or so. I close all of the seacocks in the boat when I leave ...except for the cockpit drains.

I want to congratulate you on your boat! A Shipman 28 was my first keelboat many years ago. A sweet sailing boat, quite fast and lovely. I wish you many happy voyages.

Thanks - we like her very much. We moved her to her new home yesterday and she went surprisingly well in varying conditions.
 
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