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Old 02-25-2015, 10:15 AM   #21
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Pencil zincs with steel threads?

The zincs on our Gulfstar 43 (Perkins 6.354's) when we bought it had steel threads, so that when the rest of the zinc corroded away, you could easily screw them out with a pair of pliers. But I'll be danged if I can find replacement zincs with the steel threads. Anyone know where to get these?

Alternatively, I do like the idea of using muratic acid to eat away the remainder of the zinc threads - is it really that easy? (Not as fond of using heat, although that seems viable, too.)

I just hate having to buy the new brass base every time I need to replace the zincs.

BTW - on our engines (1974 vintage), we have to cut the 2" zincs down by 1/4", or they hit something inside the HE and break off. Took me several zincs and lots of head scratching to figure that one out!
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Old 02-25-2015, 10:33 AM   #22
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New brass is a good idea as pipe threads are designed to distort with tightening. Single use type stuff. If there is no old junk inside cutting off the zinc is common.


Muriatic does dissolve the zinc and clean up the brass but unless you plan to run a die over the plug to recut the threads, which will further set the zinc into the cooler.. why bother


If you don't wait until there is nothing left you should be able to unscrew the zinc easily.
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Old 02-25-2015, 10:44 AM   #23
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Should take a 2" zinc. Did you open the Heat exchanger, take the end cap off, to see what's going on. Could be part of the broken off zinc laying in the bottom or maybe it's an aftermarket heat exchanger with different dimensions??

I've never seen the "steel" threaded zincs.

The best way I've found to remove the broken off stub is with a propane torch and an old cast iron skillet. Be sure and hold the cap with a pair of pliers facing zinc side down in the pan away from you. Heat the back of the cap until its hot and it begins to smoke, tap the bronze cap in the bottom of the pan and the melted zinc will fall out. You can use a thread chaser to clean up the threads and remove any left over zinc. I usually do 4 or 5 at a time to make it worth my time.

Be sure and do this in a well ventilated place, preferably outside and wear some eye protection and leather work gloves.
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Old 02-25-2015, 01:28 PM   #24
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Interesting thread on zincs. My new to me boat (1990 marine trader) has 2 Perkins 6.354's and I was told there were not any engine zincs to change. Could this be correct?? If there are zincs, where would they be located??
Thanks!
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Old 02-25-2015, 01:57 PM   #25
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Interesting thread on zincs. My new to me boat (1990 marine trader) has 2 Perkins 6.354's and I was told there were not any engine zincs to change. Could this be correct?? If there are zincs, where would they be located??
Thanks!
Very True. . .given the year of your boat I would assume you have Perkins 6.354-4 (Range 4) engines. If so, you probably have a manicooler instead of separate exhaust manifold and heat exchanger. You would have to confirm that though to be sure. I do not know if the manicooler had zinc pencils or not. Maybe someone else with Range 4's will respond.

Perkins did not install zinc's in their engine blocks, they're fresh water cooled and not necessary. The only zinc was a pencil zinc in the heat exchangers. Not even the original combination oil cooler had zinc. Mine are 1976 6.354-M, same basic engines, but different HE. The only zinc is in the heat exchangers and the aftermarket (replacement) oil coolers have pencil zinc.
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Old 02-25-2015, 02:50 PM   #26
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If you change the zincs before they all but disappear, you can unscrew what is left most of the time. For every 20 zincs with brass tops I buy, one or two have to be tossed and the rest I just screw a new zinc in.
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Old 02-25-2015, 03:25 PM   #27
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Thanks for the reply Edelweiss. Yes, my engines are range 4's with the manicoolers, so I guess I don't have to worry about zincs!
Thanks again!
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Old 05-11-2015, 07:48 PM   #28
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Quote:
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Muriatic does dissolve the zinc and clean up the brass but unless you plan to run a die over the plug to recut the threads, which will further set the zinc into the cooler.. why bother

If you don't wait until there is nothing left you should be able to unscrew the zinc easily.
I finally got around to buying some muratic acid (it's labeled hydrochloric acid, but the guy at the pool supplies store says it's the same thing - Google seems to concur). Plopped one of those brass plugs in, and man, did it go to town on the zinc that remained in the plug! I now have three clean brass plugs, ready for the cheap screw-in pencil zincs. (As for recutting the threads, bayview - I think I'll take my chances that they'll still seal just fine without that. I don't think there's all that much pressure building up in the heat exchanger.)
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Old 05-12-2015, 01:56 AM   #29
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Just a little warning - putting zinc in acid produces hydrogen gas, lots of it. It's how we used to make "UFOs" when we were kids. Hold a dry cleaning bag over the reaction vessel and fill it with hydrogen, seal the bottom and let go. Extremely explosive! Be careful!
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Old 05-12-2015, 07:51 AM   #30
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Just a little warning - putting zinc in acid produces hydrogen gas, lots of it. It's how we used to make "UFOs" when we were kids. Hold a dry cleaning bag over the reaction vessel and fill it with hydrogen, seal the bottom and let go. Extremely explosive! Be careful!
So if I filled a really BIG bag with it, it could lift me up? ("Oh, the humanity!")

Thanks for the warning. The smell, and the feel in my nose, of the first whiff told me to stay the heck away from it, but I didn't think about it being explosive. Next time, I'll do it outside instead of in the kitchen.
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Old 05-12-2015, 08:42 AM   #31
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I haven't read all the replies but what you see is the result of the water mostly draining out of the cooler with the engine off leaving only a bit of zinc immersed and protecting. So the lower part gets used up then the top brakes off.


You need to change them more often and rodding out that cooler would not be a bad idea.
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Old 05-12-2015, 09:25 AM   #32
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I haven't read all the replies but what you see is the result of the water mostly draining out of the cooler with the engine off leaving only a bit of zinc immersed and protecting. So the lower part gets used up then the top breaks off.

You need to change them more often and rodding out that cooler would not be a bad idea.
That may be correct in some situations, but not this one. The heat exchanger is pretty much full all the time, even when the engine is cool, so that the zinc is mostly submerged all the time. And the heat exchanger was totally rebuilt just a year ago, so I'm pretty sure it doesn't need it again so soon.
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Old 05-12-2015, 04:06 PM   #33
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You may have a little stray current running around on that one engine...give it a good cleaning, replace all terminal blocks and wire ends,,,

Before all that I guess you could disconnect all grounds and see if there's any current between the block and a ground wire....
That would certainly be on my list!
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Old 07-16-2016, 07:43 PM   #34
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Read the whole thread and not anywhere that I find is there any information of 'What zinc a Perkins 4-236 needs by nomenclature. One party off the thread, in conversation said the NAPA parts store has these zincs. Okay.can one give a description, size, or actual manufacture name when I go into ask? thanks,

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Old 07-16-2016, 08:04 PM   #35
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I get mine here Zinc Anodes, Boat Zincs, Marine Anodes at ZincWarehouse
About $3-5 for my Detroits. They also have aluminum and magnesium. Way cheaper than oem, etc.
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Old 07-16-2016, 08:09 PM   #36
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I get mine here Zinc Anodes, Boat Zincs, Marine Anodes at ZincWarehouse
About $3-5 for my Detroits. They also have aluminum and magnesium. Way cheaper than oem, etc.
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Old 07-17-2016, 01:47 AM   #37
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Ditto!!

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Old 07-17-2016, 04:58 AM   #38
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Engine Anode Failure?

Hello Gulfstar 36,

I can see your anode problem, but I think you are missing the condition of your HE tubes!, I would say you are in dire need of a good flush/clean to get the HE Tubes working again to transfer the heat from your fresh water re-circ system to to the raw water running through your HE!.

You can actually make your own Anodes from Zinc Bar Stock, you can usually buy any diameter Zinc Bar from most anode supply companies to suit you application, you can cut them to length then use a suitable die nut to cut the corresponding thread to suit your Anode adaptor, as Xsbank mentioned, check them at 3 mth. intervals until you establish the eroding/loss cycle on your engine, I would also recommend an electrolysis test at some stage to give you an idea of your vessels negative mv value perhaps pre-slipping then post to correlate your normal anode replacement regime to see if you are within values that last the season?.

Please note: I do not recommend Muriatic Acid as a stripper for HE systems, reason it is very harsh on Aluminium etc. and is not completely neutralized simply by flushing with fresh or salt water, it can still carry on reacting with Aluminium etc. to their detriment effecting sealing surfaces etc. - There are safer solutions commercially available ie: Acetic Acid and Phosphoric Acid at the recommended dilutions with water that you can re-circulate in your Raw Water system that will strip the whole system without removing your HE, G/B Cooler, After Cooler etc. this process will save you money if carried out with the right concentrations and flow rates/direction etc. to regenerated your raw water systems ability to transfer your engines heat to maintain normal running temps, see att. pic. using Phoshoric Acid 5:1, these pics. were taken pre-flush then 2 hrs. later. on a Cummins 555, this process eliminates the physical removal of you engines HE's - G/B etc.





This flush rectified over heating symptoms immediately, the owner now carries out this procedure annually, I still recommend a physical check by removing HE end plates occasionally to confirm flush has been successful and to ensure health of HE Tube patency Silver Solder etc. and HE Housing.

I hope this helps?.
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Old 07-18-2016, 12:11 PM   #39
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This zinc anode was in-service exactly 12 months. Look how it was chewed off at the base but the anode looks mostly intact. This is a Perkins 4.236. I would hope it would have wore down all over.
You may have a problem I had once - On that style of heat exchanger if the zinc is a little too long it will contact the center cap bolt and when you tighten the brass zinc holder, the zinc breaks off at the base.

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