Stuck engine zinc

[horsemel]

While replacing my water heater on Friday June 11 I decided to replace the engine zinc after I did the water heater.  (The water heater was easy after I got the hoses mentioned in a previous post.)  However, the zinc is screwed in tight and I can not loosen it without using a lot of force.  Since we were leaving on a one week cruise the following day I decided to not mess with it further.  Question:  How much force is safe to put on that zinc considering where it is attached?  I don't want to strong arm it and regret it.  Makes me wonder if the previoius owners never replaced the zinc.  Since the thing is located on the bottom I don't see how I would get penetrating oil to it.
Mark Mueller

[Bob K]

Mark,
Try removing it after the engine is run for a while and the HX is warmed up.  That did the trick for me when I had the same problem.

[SeaFever]

If time permits, you could take the HE out and then handle the zinc. I too had the same issue when I got my engine (used). I took the HE off and then got the zinc out. When I did get the zinc out, only the head of the bolt came off and the rest remained inside. I had to drill and tap the same, clean the HE out and then replaced with a new zinc. Note when you do drill and tap, be very careful, the matrial you are drilling out is zinc, that is very soft. In my case I kind of tapped it with a bit of gusto. So when I replace the zinc, it would leak a bit. However, just tightening it a bit more dd the job. Just FYI.

[Stu Jackson]

The bolt head you see is bronze and you can whack the heck out of it to make it move.  The softer zinc is screwed into the inside of the bolt head, they are two separate pieces.  Hammer away.  Mahendra's idea works if your threads are gone, and mark's idea to wait until it is warmed up will work if you can't do it cold.  I used to use a box end wrench, graduated to a socket set.  11/16" head as I recall.

[Indian Falls]

Mine was original, it still had the brown/gold block paint on it.  It was tough and you have no leverage in the postion you're in trying to wrench it out.  I did not use heat or penetrant.  Use a 6point socket if you can get one on there.  My motor mount bolt would not let me get one on there.  I was able to use a vise grip and a metal tube for added leverage to get it out.
The zinc was so corroded it stayed inside the HX.  I popped both covers off the ends and fished out the old zinc bits and 6 or so impeller blades.  I got the zinc at catalina direct and I did not have to cut it down.

The HX body looks like cast iron so it should be tough enough to hold up to the wrenching.

Hope this helps!

[Ron Hill]

Mark : As Stu mentioned you can really "wack" the bronze Zn holder. 
Just make sure that you are using a socket or a box wrench so you have pressure on all 6 sides.  Best to use a 6 sided (rather than a 12 point).  It should be 11/16" size. 
You only need to tighten the new one so the leaking raw water stops.  Make sure that you clean the inside threads on the HX before you screw in the new Zn.  I like to use a battery terminal brush as it'll go into the threads.  You want a good electrical contact so don't use Teflon tape. 
A few thoughts

[Bill Asbury]

Mark, the bronze bolt head on the zinc in my HX was hard to get to and hard to break loose but I persevered in using a ratcheting box end wrench and finally broke it loose.  No zinc left on the bolt, but bits and pieces in the HX, which I cleaned out.  Got a new zinc from local Universal dealer.  Important to check zinc length which may need to be shortened with hacksaw.  If zinc is too long it will break off the bolt when you screw it in.
Bill

[Ron Hill]

Guys : Bill has a point that if the Zn is too long it may break off in the inside of the HX.  On the other hand if too long it could also put a indentation or worse could fracture the internal coolant tubing inside the HX. 
All you have to do is remove the old Zn holder, take #2 pencil and insert it into the hole.  Note how far the pencil goes in and measure it against the new Zn.  Then make sure the new Zn in the holder is slightly shorter than the pencil distance.  A thought

[Hawk]

I purchase a number of the zincs without the brass nut and cut them all to length having followed Rons pencil measurement procedure some years ago. The brass nut can be re-used many times particularly if you change the zinc twice a year as it won't seize on to the HX. I've read that it is not considered fanatical to change it once it is half gone, which in my marina is every 7 to 8 months or so.

Tom

[Bob K]

Boatzincs.com has pencil zincs of various lengths. You can buy the size that fits without having to cut.  Their zincs are MUCH cheaper than WH, even w/ shipping. I buy several years worth at a time.

[horsemel]

Thanks guys, I will give it a shot this weekend while the Admiral is off playing with the gals.  I was mainly worried about putting too much stress on the HX by cranking too hard on the zinc.  I will let you know the results.
Mark Mueller

[Ron Hill]

Mark : The bronze Zn holder is a tapered pipe thread, so once you break the seal it should come out easily.  A thought

[SeaFever]

Here is an interesting thing I observed on my HE while changing the zinc. I found that the end of the new zinc was touching the side of the tubes inside the HE. Effectively in the last few threads that was kinking the shaft of the zinc, and hence the bolt holding the zinc, sideways. This resulted in water drops coming out of the bolt/zinc. I had found this out by using a cylindrical rod and checking the depth accurately (this is what Ron is suggesting by using a pencil) I used a normal file and filed the zinc at the tip just like a pencil sharpener does, only a steeper angle. Once that was done the zinc did not touch the inside of the HE and there was no leak!

Just thought I would share. Note that all this was easy for me to do since my engine was in my garage on a wooden frame with wheels I built for it...

[Tony Benoit]

Hello All,

I just changed the zinc in my HX.  I get a standard 1/4 inch pencil (refers to the thread diameter) and cut it down to 1-3/16" length.  If I leave it any longer it will either jam and not go in or it will go in and prevent the brass plug from seating properly.

I have tried to use one of the new plugs that one can buy with a zinc, but none have ever fit properly.  Instead, I clean up the original plug best I can and re-insert it.  I snug it hand-tight, then gently take about 1/2 to 3/4 of a turn with a open end wrench.  I let the exchanger warm up before making the last little tweaks.  It is way too easy to over-tighten the plug or to foul-thread it.  I need to be sure that it is turning freely by hand before snugging it up.

Once or twice I have found that the remnants of the old zinc stayed behind when I removed the plug.  In each case, I opened the raw water valve and out popped the old zinc with a blast of seawater.

Thanks,

Tony
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Helen C
'89 Standard/Wing #903