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Pencil zinc size

J

jgreen

New member
Hi All,
New to the forum and tackling some maintenance issues on 1987 Chris Craft 336 with twin 350 (454)
I need to replace the H/Exchanger zincs. Does anyone know the correct size and a good source?
Thanks!
 
Pull one of the old ones out, and take it with you. You'll find both 1/4" and 3/8" TP threads being used for these.

Couple of things that I have observed with these:

The brass pipe threaded section will always be OK and will always be tapered pipe threads.
However, I've found that the actual replacement pencil anode threads will vary from one manufacturer to another.
When you pick up the new anodes, purchase a hand full of extra pencil anodes. This way these will fit the brass portion in the future.

The other thing is the length.
Sometimes the H/E won't allow for a full length anode, and we end up shortening the anode as to prevent it from bottoming out and breaking when screwed in fully.

.
 
Last edited:
RicardoMarine said:
Pull one of the old ones out, and take it with you. You'll find both 1/4" and 3/8" TP threads being used for these.

Couple of things that I have observed with these:

The brass pipe threaded section will always be OK and will always be tapered pipe threads.
However, I've found that the actual replacement pencil anode threads will vary from one manufacturer to another.
When you pick up the new anodes, purchase a hand full of extra pencil anodes. This way these will fit the brass portion in the future.

The other thing is the length.
Sometimes the H/E won't allow for a full length anode, and we end up shortening the anode as to prevent it from bottoming out and breaking when screwed in fully.

.
Click to expand...
One more dumb question. Can I take the zinc out while I match to a replacement without the boat sinking? (go easy on me - I just switched from 25 years of racing cars. Those I understand and when something went wrong it didn't go to the bottom of a river)
 
buy E-1 zincs for the HX and get some E-0 ones for the oil cooler. change both at the same time and it will eliminate a lot of issues. some shops will carry just the pencils - a much better option if you have the time.
 
Since this appears to be the first time you have replaced the zincs in the heat exchanger, I would recommend removing the end cap of the exchanger on the end where the zinc is so you can check for pieces of old zincs that should be removed. This way you can make sure the new zinc doesn't top out. You can also get a look at the condition of the cooling tubes for any that may be blocked. Yes, this can all be done while in the water and you don't even have to close the sea water valve. The boat will not sink but a little raw water will come out when the zinc is removed...about a cup or so.
 
Jgreen, I agree with erich.
Open the end plates up and take a peek at the tube bundle.

Also, pull these pencil anodes part way through your season, and inspect them. You may find that they require replacement more than once per season.
A few pencil anodes per season is much cheaper than an H/E replacement.
And NO teflon tape on the threads... they must make continuity with the shell/tube.

.
 
RicardoMarine said:
Jgreen, I agree with erich.
Open the end plates up and take a peek at the tube bundle.

Also, pull these pencil anodes part way through your season, and inspect them. You may find that they require replacement more than once per season.
A few pencil anodes per season is much cheaper than an H/E replacement.
And NO teflon tape on the threads... they must make continuity with the shell/tube.

.
Click to expand...

I purchased new complete pencil zincs and also some zinc only replacements The complete ones came with teflon tape already installed. I have read elsewhere that once tightened up the threads will cut through the tape and make a good seal and also good electrical contact. So as a test I connected an ohmeter between the end cap cover nut and the zinc bolt...good connection.

Erich
 
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