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Old 12-12-2008, 04:20   #16
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Make sure after you free it that you operate all through hulls regularly. Its amazing how fast they will become stiff or not operate at all. A weekly operation will keep things working smoothly. The flexing isnt totally indicative of a too thin hull but maybe a rotten backing plate, The main engine throughhull did the same flexing because the plywood backing plate was soft. I replaced the plywood with a plate made of fiberglass. I took a plastic storage container and laid up 1/2" of fiberglass in the bottom, popped out the fiberglass and after removing old through hull and grinding hull pushed the glass,hole predrilled into a fiber mush made of aerosil. Then installed SEACOCK instead of ball valve and through hull bedded with 5200. I did all the grinding and installation at low tide with the boat standing on a sandbar supported by kedging anchors out the sides with polyester line, nylon doesnt work for this too stretchy. Found that out during a scary episode!!! ps absolutely no valve movement after this treatment.
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Old 12-12-2008, 04:21   #17
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Originally Posted by GreatKetch View Post
If these are really metal ball valves with metal handles, attached to metal thru-hulls, I am going to politely disagree with Ex-Calif, and tell you that you really can't break them by appling torque with just hand pressure. Push on them as hard as you want--BY HAND. If you put a wrench on them, then all bets are off.
Sorry to disagree Great Ketch, bought my boat 3 months ago, survey said thru hulls/ball valves needed attention possibly replacement, insurance co asked what I was going to do with them, So I hauled out and had them replaced, thru hulls were ok, but ball valves needed replacing, shipwright said I will just see if this one will come unstuck, it came unstuck allright, the whole thing came off in his hand, there we were staring through the thru hull to the ground below, so obviously there was more corrosion than what we could see, no wrench used just brute HAND force. be carefull!!!
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Old 12-12-2008, 05:59   #18
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Approximate fluid flow thru an orifice

Boy, Stillraining knows how to push my buttons. Ok, making lots of assumptions, try this formula:

Q=15 times A times the square root of h where Q equals the quantity of flow in gallons per minute, 15 is a parameter that lumps assumptions about the shape of the orifice and its length, the fluid (seawater) and some other fluid flow parameters and the various units, A is the size of the orifice in square inches, and h is the head in feet.

Example: A for a 1.5-inch opening is 1.77. If the opening was 3 feet below the surface the square root of 3 equals 1.73, or Q=15(1.77)(1.73), Q= 46 gallons per minute.

For 2-inch diameter A=3.14, same head and Q=81.5 gallons per minute.

Does this help?
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Old 12-12-2008, 06:54   #19
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Originally Posted by HorizonMarine View Post
You don't need to haul a boat to change a thru hull valve. We change them all the time for customers in the water. Have your new one ready to go, liquid teflon in the threads. (can't use tape because its the female thread). Unscrew the old one and put your hand over the hole. slid your hand out and screw the new one in. It works best if you have the new valve in the closed position. Sometimes the handle is in the way and you can remove it or leave it open and put a plug in it.

Of course if there are any problems you can easily stick a wood plug in the old hole and regroup.

FYI, You can even add a thru hull withouy hauling, including drilling etc, but it requires a divers help for 1/ hour.
I have about 18 below water line brass through hulls of various sizes on my 1993 sailboat (not that old compared with other cruisers boats). All have associated ball valves. I have replaced maybe half of them now. In every case bar one (a little half inch valve) I have had to carefully grind off the outer flange in order to release the unit (usually through hull to right angle union to ball valve to hose adaptor). Even then I have had to use the largest vice I could find with long pole as lever to unscrew the old parts. How you could get even remotely close to applying this much force within the tight confines of a boat I don't know.

My advice therefore - don't even consider doing the job in the water if the boat is more than a couple of years old. Work the valves regularly. As toilet outlet ones seem to suffer the most, put a little olive oil into the pan & flush with the valve partly closed to coat the surface of the ball, then work it some more. As soon as a valve starts to stiffen up it will only get worse so mark it as job to do at next haul-out.

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Old 12-12-2008, 07:48   #20
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Richard, you nailed it. The head discharge is the one thats stuck solid and the galley sink discharge is the one that moves a little.

Dan, they do appear to be seperate valves and thru-hulls. Its not a flimsy little Home Depot valve but a large heavy one. As you noted, I am more concerned with cracking the hull than breaking the valve.

Cowboy, all that stuff you wrote is very interesting but I can't see how it applies to my problem. I will not be opening any holes in the hull while the boat is in the water unless its an emergency.

I did get this boat surveyed ($600 for a 31' boat) by Fred Hecklinger in Annapolis. I have found many things he missed in the last couple of weeks. There are a few cotter pins here and there, but mostly vacant holes or straighted out rings on all rigging and lifelines. It seems like a surveyor might have noticed that. He also missed all the fuel running down the side of the engine from leaking banjo fittings.
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Old 12-12-2008, 09:52   #21
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If the head valve is stuck it is a pretty good bet there is major calcium build up inside the valve from a combination of urine and salt water. If you find a diver in the area working close to your boat you may be able to get him to try and clean it out. It will eventually clog the entire thru-hull, but you should not be discharging overboard anyway. You might also consider a quick haul at a marina. Let them haul you to either repair the valve or replace it with the boat in the slings over their lunch hour. Otherwise hang a tapered plug on it and take care of it on the next haul out.
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Old 12-12-2008, 13:55   #22
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Originally Posted by Cowboy Sailer View Post
Boy, Stillraining knows how to push my buttons. Ok, making lots of assumptions, try this formula:

Q=15 times A times the square root of h where Q equals the quantity of flow in gallons per minute, 15 is a parameter that lumps assumptions about the shape of the orifice and its length, the fluid (seawater) and some other fluid flow parameters and the various units, A is the size of the orifice in square inches, and h is the head in feet.

Example: A for a 1.5-inch opening is 1.77. If the opening was 3 feet below the surface the square root of 3 equals 1.73, or Q=15(1.77)(1.73), Q= 46 gallons per minute.

For 2-inch diameter A=3.14, same head and Q=81.5 gallons per minute.

Does this help?
Immensely...now make me a chart.....or I'll push some of your hot buttons..

A while back a poster wanted to have pumps capable of keeping up with a one foot diamiter hole...I laughed to myself but kindly told him he could not carry large enough pumps to do it...I was looking for a formula I understood or a table to prove that point and could not find one..

So Thanks..

Just for grins what would it be @ 3' of head ?...I will try myself and see if I get the same answer with my rudimentary math skills and you formula.
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Old 12-12-2008, 13:59   #23
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2933 gpm?

Sounds very reasonalbal... that is almost 176,000 gal per hour..thats a big rule pump boys..
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Old 12-12-2008, 14:54   #24
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As much as I may be accused of drifting...a cup or less of cheap white vinager partially flushed into the head, left to sit for 15- 30 minutes . then a few drops of olive oil to lubricate once a month is old school maintenence.
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Old 12-12-2008, 15:26   #25
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Jim, That is great advice for maintenance but won't help a stuck valve.
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Old 12-12-2008, 15:41   #26
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stuck ball valve

If you are going to exert any force on the valve you must use a pipe wrench or other suitable tool to support the valve. That way any torque will be absorbed by the wrench. hope this helps. If the ball moves a little keep working it and use lots of liquid wrench or other penetrating oil. Patience pays off. Some heat may help but if there are any nylon seals a hair dryer may be as much heat as you can safely apply. Good luck
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Old 13-12-2008, 01:50   #27
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More fluid flow

Actually, Stillraining, in the case of a very large opening like that the “K” factor that I said would be about 15 for a incrusted thru hull of 1˝ inches diameter would be about 20 for a 1 ft diameter hole in the hull. The formula then becomes Q=KAÖh with K=20 instead of 15.
So we have A=113 in2 for a 12 inch diameter hole, 1.73 for Ö3 ft of head and Q=20(113)(1.73)=3910 gallons/minute. I remember that post and his requirements. I remember thinking, “Engine driven pump, driven by the diesel, big hoses”

I was trained in fighting oil-well fires. An 1 ˝-inch nozzle at 200 lbs/sq. in. can move a lot of water. (It can also move a man holding on to the nozzle if he is on slippery ground!) The K for a well made nozzle and water might be more like 40. So, in the case of a 1 ˝-in diameter nozzle at 200 lbs/sq. (or a head of 460 ft) we have: Q=40(1.77)Ö460=1518 gallons/minute, less than half what is needed.

So, back to the guy pumping out his big hole in the hull – big hoses, big pump; but it is possible. With the right set up he could have the worlds first jetboat-sailboat!

Here is a link to a simple derivation of the formula http://www.mcnallyinstitute.com/13-html/13-12.htm

Now you can do it all by yourself! You know, McNally should be a member of this forum.

Fair winds. (Sorry about the thread drift. It is Stillraining's fault!)
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Old 13-12-2008, 08:16   #28
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You didn't mention if the through hulls are in the open or closed position. If you are lucky enough to have them frozen in the closed position a very simple solution is to very carfully losen the clamps on the hose where it is meeting the through hull. You want to determine if there is any water pressure. Once you have determined that there is a good seal with the (Old Seacock) remove the hose and very liberally spray a good quality pertolium based lubricant, (WD 40, PB Blaster, Liquid Wrench) down into and on to the insides of the valve. With the understanding that patience is the key here re-attach and clamp the hose back on. Now it is time to sit back and wait, this may take hours it may take days. Every so often try to by hand (Never force the valve) see if the valve is starting to move. Don't be affraid to repeat the procedure often until the valve starts moving freely again.
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Old 13-12-2008, 11:35   #29
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If these are really metal ball valves with metal handles, attached to metal thru-hulls, I am going to politely disagree with Ex-Calif, and tell you that you really can't break them by appling torque with just hand pressure. Push on them as hard as you want--BY HAND.
I was recently on a survey sea trial on a 1970s vintage boat with the original metal seacocks still in place. The surveyor was testing one, by hand and it fractured without coming completely off, making a wood plug useless. Neither the electric or manual bilge pump were working, so it was an exciting ride back!

Later after it was broken off completely we cold see how corroded it was. My guess is stray current was at work. The metal was pinkish almost all the way through. It was a good wake up call in the value of properly functioning thru-hull systems. My point being, you never know for sure what may happen when you are in the water and start forcing something.

It was only one of the many reasons I walked away from that boat.

Personally, I'd either haul and replace or fix them or If I felt very comfortable with the hose, etc. and was on the boat most all the time with a plug handy might continue on. What you are comfortable with however, is your call. I don't think anyone here can decide that for you.
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