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Old 08-12-2015, 01:30 PM   #1
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Well that's not good...

Morning all, today's order of business was to check/change out my zinc pencils this on my single FL120. First one, forward, was about half gone and swapped it out with a fresh pencil. Went around back to the rear cooler and when I removed the pencil, all I got was the brass head. Figuring it was just another item that the PO neglected, I dropped in a fresh pencil, which went in just fine, and began to tighten. About halfway down the thread, I felt a split second bit of resistance but then it continued to tighten. Something in that head of mine said something wasn't right so I removed the pencil and, you guessed it, I got just a brass cap with a tiny bit of zinc sticking out past the bottom thread. Thus the title of this thread.
I removed the remaining pencil from the cap and installed the cap just fine so I'm thinking the pencil was probably about 1/4" too long.
So, for now, is it safe to operate the engine this way as long as I regularly check the zinc to see when it is gone? Or, do I dare try and thread something into the pencil in an attempt to remove it and replace it with a shortened version???
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Old 08-12-2015, 01:38 PM   #2
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Actually the zinc won't do any good unless it's electrically attached to the thing it's protecting.
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Old 08-12-2015, 02:08 PM   #3
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You need to remove the end cap of the heat exchanger. You will probably find a pile of old broken zincs. You might as well take off the other end cap and rod out the tubes with a wooden dowel. Where is your front zinc? I don't have one. When you screw the zinc into the cap use a pliers to be sure it is tight. I did one hand tight and it vibrated out.
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Old 08-12-2015, 02:48 PM   #4
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Greetings,
Mr. Ss. Yup, Mr. m's got it right. Remove the end caps and at least take a look. Remove the pieces of the anode(s) and try to install a new anode, while watching your clearance. Not a big deal to hacksaw off a small piece to allow proper fit (saw off the blunt end, NOT the threaded end ) It may not be necessary to "rod" your tube bundle but an inspection will determine that.
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Old 08-12-2015, 08:09 PM   #5
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Our 1973-vintage FL120s have only one zinc apiece, and it's in the main heat exchanger mounted across the rear of the engine.

There are, or used to be, oil and transmission fluid coolers that can accommodate a zinc but the cupro-nickel exchangers we buy from American Diesel do not have this feature.

The only issue we've had with the main heat exchanger zincs is the larger diameter ones "growing" in diameter as the zinc breaks down which can cause them to jam in the hole. So when the cap is unscrewed it unscrews from the exchanger and the zinc at the same time. So the zinc is sitting there in the hole and can easily drop through into the body of the exchanger as one tries to remove it.

We've had this happen a couple of times--- we didn't do anything about it figuring it will either eventually disappear or it will just lie there-- and then we switched to zinc pencils that are thinner and so will not jam in the hole no matter how deteriorated and "fuzzy" they get.

We also write the date the zinc was replaced on the top of the cap with a Sharpie so we have an idea of how long it's been in there and when we should inspect it for replacement.
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Old 08-13-2015, 04:51 AM   #6
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As usual, good call guys. I took the cap off and this is what I found. As I attempted to put in a new pencil, I found that the bottom of it was hitting the brass center cone where the cap bolt screws in. I chopped off a 1/4" of the pencil and it went in fine. I went ahead and rodded the tubes as I figured might as well just take care of everything now so I will know when it was done last and done right. Also went and checked the strainer while I was at it and Holy Cow! I pulled a wad of crap out of it I'm a new boat owner and trying to learn everything I can on the fly. I would highly recommend that if you are like me, then read as much as you can on this forum and just go through everything on your boat right after you buy it. I had high hopes for the PO and have been sorely disappointed in his complete lack of even some of the more simple preventative maint.
Marin, you are correct. The forward zinc pencil that I had referenced in my initial post was for the oil cooler. Mollie is a vintage '77 and it appears to be OEM.
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Old 08-13-2015, 07:11 AM   #7
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I am also new at this I brought over a mechanic to help with this the gene has one in its heat exchanger, poped the cap and it was nasty in there going to descale it! I have perkins sabres only found a pencil which was gone after the strainer. Is there another some where else and should I assume that the heat exchangers have to be removed and descaled as well oh the gennie is a westerbek 12 kw
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Old 08-13-2015, 08:42 AM   #8
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Although TF is a great source for info, a $25/yr subscription to Boat Diesel
will pay off in spades.
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Old 08-13-2015, 09:12 AM   #9
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Quote:
Originally Posted by Soulshine View Post
I'm a new boat owner and trying to learn everything I can on the fly. I would highly recommend that if you are like me, then read as much as you can on this forum and just go through everything on your boat right after you buy it.
You are so right on that one, Soulshine. I spend way too much time on here but I can't get enough. Even this little exercise you went through educated me. And Marin's little ditty about his pencil swelling when he sticks it in...
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Old 08-13-2015, 09:44 AM   #10
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Originally Posted by Codger2 View Post
Although TF is a great source for info, a $25/yr subscription to Boat Diesel
will pay off in spades.



Anyone that thinks otherwise is simply being penny wise and pound foolish IMO.
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Old 08-13-2015, 09:54 AM   #11
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Even mechanics leave the old stuff inside to blok the cooler. The customer doesn't like it when a mechanic says I have to do an extra hours work to do this right.
My boat was the same when I bought it.
For removing a zinc that separates from the brass cap a threaded rod junction nut is helpful if you can get one in the correct thread size.
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Old 08-14-2015, 08:40 PM   #12
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Quote:
Originally Posted by Marin View Post
Our 1973-vintage FL120s have only one zinc apiece, and it's in the main heat exchanger mounted across the rear of the engine.

There are, or used to be, oil and transmission fluid coolers that can accommodate a zinc but the cupro-nickel exchangers we buy from American Diesel do not have this feature.

The only issue we've had with the main heat exchanger zincs is the larger diameter ones "growing" in diameter as the zinc breaks down which can cause them to jam in the hole. So when the cap is unscrewed it unscrews from the exchanger and the zinc at the same time. So the zinc is sitting there in the hole and can easily drop through into the body of the exchanger as one tries to remove it.

We've had this happen a couple of times--- we didn't do anything about it figuring it will either eventually disappear or it will just lie there-- and then we switched to zinc pencils that are thinner and so will not jam in the hole no matter how deteriorated and "fuzzy" they get.

We also write the date the zinc was replaced on the top of the cap with a Sharpie so we have an idea of how long it's been in there and when we should inspect it for replacement.

Good to know .


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