Conference unifix::sailing

    We did this last year ourselves.  The biggest pain was access.  We used
    a combination of very large crecent and pipe wrenches.  The biggest
    problem you may run into is probably dislodging the through hull which
    is possible if you apply tourque at odd angles.  Another way to get
    them off is if you can partially disassemble the body so there is an
    opening on the side available, a long pipe may provide the leverage you
    need to turn the beasts off.  All in all, it was not that bad of a job
    once I was in position.  Just getting it started is the hard part. 
    Once the bond broke, they spun off fairly easily.  Don't forget to use 
    penetrating oil well in advance.  Every little bit helps.   
    
    Brian

re .0:

There is another method that is usually quite successful -- brute force. 
If it doesn't work, you aren't using enough of it. I assume you aren't 
trying to save the gate valves (if you are, you shouldn't). Find a big 
pipe wrench and start twisting. If the thru-hull breaks off, it was 
corroded and needed replacing anyway. Probably the gate valve will 
unscrew. Bronze doesn't corrode together the way ferrous metels rust 
together (in my somewhat limited experience -- with bronze, not rust). 
Your biggest problem will be finding enough clearance to use the wrench. 
This reply may sound less than serious, but it is exactly how I would 
proceed. Using heat (propane torch or electric heat gun) strikes me as 
overly risky. Using brute force you'll at worst destroy the thru-hull
fitting. I've never found penetrating oil useful for anything other than 
making a mess, but then I don't always have a lot of patience.

Alan

    
    You will probably mangle it anyway, so simply grind the head off
    from the outside. A new thruhull will make you feel safe!
    

    .... and the next question, I think, is how to avoid having the thing
    seize up in the first place.... 
    
    I've been putting this off, too....
    
    Ron
    

    I think you will find that if it is at all accessible, that it really
    doesn't take much more than alot of elbow grease and a large lever.  We
    thought this was going to be impossible on the sea water inlet for the
    deck wash and the raw water inlet for the engine.  There was no need to 
    mangle the through hull. Just twist and grunt.  A large pipe wrench can
    get around the body of the valve where a large, very large in our case,
    crecent wrench will only work on the base.  When you put the new 
    valve back on, use teflon tape or similar to seal it.  
    
    Brian

I believe that your husband's expectation of problems is his 
biggest problem. I recently changed all of my gate valves 
and found that they were easily removed. At worst, a through 
hull fitting turned and broke the hull seal requiring it to be 
loosened and resealed. In general, not a big job. I changed 4 
valves in less than an hour (alone).

Note, I replaced my gate valves with PVC ball valves. I don't 
recommend gate valves because they have high failure rates. 

Joe

re .4:

There is a product called Never-Seez that is quite effective in 
preventing corrosion in threaded assemblies. For example, stainless
steel screws in aluminum tend to be very difficult to remove (such as
the cover screws on our engine's sea water pump). With Never-Seez
slathered liberally on the screw threads the screws are easy to remove,
even after some years. 

    re.7
    Will Never-seez work on screws that have already corroded in
    aluminum?
    
    The screw which hold my screens into the Bomar ports have seized
    up and I can't move them.

re .8:

>>>    Will Never-seez work on screws that have already corroded in
>>>    aluminum?
    
>>>    The screw which hold my screens into the Bomar ports have seized
>>>    up and I can't move them.

Uh, no, sorry. Never-Seez (there are other trade names for the same 
stuff) has to be applied before assembly as it is a thick paste or 
grease. Never-Seez has a working temperature range of -200 deg to 1000 
deg F. 

If you are lubricating threaded assemblies that live at ambient 
temperature, try anhydrous lanolin, available at drug stores. This stuff 
is really quite effective in preventing galling and corrosion. I use it 
on my turnbuckle threads. At the end of the summer the turnbuckles 
loosen with nary a complaint. Since anhydrous lanolin is used in 
cosmetics, it is nice to your skin. Just wipe off the excess and rub the 
rest in. 

    If you use these antiseeze compounds, please insure that there is some
    friction device (i.e. locknut) to hold the screw in place. I used this
    on a sail trac device and the screw loosen, elongating the threads in
    the aluminum.  
    
       john

    I did not see .7 get answered and I have umpteen stainless screws that
    nature has welded into various pieces of aluminium on my boat.
    
    My usual approach is:
    
    Penetrating Oil & Tapping gently with a hammer 
    Brute force - just makes it worse as the head comes off the screw
    Penetrating oil & beating the heck out of it with a hammer
    Heat
    lastly - drilling/sawing and te-tapping the hole.
    
    I have a winch that needs to be moved but I just ignore it because it
    is stuck.  
    
    Any ideas ?

re -.1:

Once stainless steel and aluminum have corroded together, getting them
apart can be difficult to impossible. Even a lot of heat may fail (it
has for me), and the amount of brute force needed may exceed the
strength of the parts (it has for me). Drilling and (re)tapping may be
the only answer (it was for me). With the right (expensive) equipment,
holes in aluminum masts or whatever can be easily filled by welding
without any heat distortion. Our mast used to have more holes than it
does today. 

      in the motorcycle world, all those ss bolts go into aluminum. To take
    out any old ones requires a soaking in liquid wrench followed by the
    use of an impact wrench with the proper point. Hammering and then
    screwing just doesn't cut it.
    
        When reinstalling, don't forget lots of anti-seize paste. Make sure 
    you get it all over the threads before assembly.
    
    
    john
    

re .13:

Motorcycle engines was where I first met steel screws in aluminum.
They mostly don't live in as salty an environment as boats do. Even with
an air impact wrench, stainless screws corroded into aluminum can be
impossible to remove. I had to use a 4 ton hydraulic press to get an
aluminum mast compression sleeve off a 1/2 inch stainless steel bolt. I
once saw an aluminum mast with a bronze spinnaker pole track. Wow, was
that a corroded mess! Thorough bedding of fittings to keep water out
helps, too. 

    Sailing Supply of San Diego, Ca. has a product made especially for
    stainless steel screws in aluninum, its called "ALUMILASTIC C".  I have
    mast steps (my own design) on a 53' stick and have used this product
    for the first set of steps 6 years ago and have no "puffing" to
    indicate corrosion.
    
    Jay