Zinc in cooling system

[reedbr]

The previous owner of my boat said I should check the zinc in the heat exchanger of the engine cooling system.  I found only one partial reference to this zinc searching the forum but no details.  I haven't found it in my manual yet either.  Can anybody shed a little more light on this for me?

C34 mkII "Ambitious"
Solomons, MD

[Stu Jackson]

ENGINE ZINCS

You also need to search the main website, which has a ton of information.

A search on zincs shows:  http://www.c34.org/faq-pages/faq-zinc.html

It's all there for you.

If you join the International Association, you also get a free CD-ROM with all of the main website information on it for viewing and learning off line.

Stu

[Roc]

I see you have a MkII, same as I do.  On the M35B engine, the zinc is located on the bottom of the heat exchanger on the right side of it while facing forward.  It's right near the fuel hoses that lead from the Racor filter.  It's right next to the throttle cable as the cable passes by the heat exchanger (the cable is always in the way when I change my zinc).  From the outside, it is just a brass colored bolt. Just unscrew the bolt and attached to it will be the pencil shaped zinc (provided it hasn't worn away).  If you haven't checked it in a while, chances are it won't be there.  When you take the bolt off, you'll just take off what looks like a plain bolt head with threads attached. Also, if my memory serves me correctly, the instruction manual does show where the zinc is.  There are two pictures showing what one looks like when still usable, and what one looks like when it's time to replace.

Hope this helps.

Roc-

[reedbr]

Many thanks.  I seem to have been using the wrong search button.  The one on the main page works much better (thanks Stu).  Thanks for the MkII info Roc.  I was looking for something to do this weekend...

C34 mkII "Ambitious"
Solomons, MD

[Stu Jackson]

SEARCH ENGINES

There is no "wrong" seacrh engine.

This site has TWO.

One is for the main website.

The other is for just the Message Board.

Please use both to gain the most information on your topic.

The 'site engine has a built-in word or exact phrase feature, while the MB engine needs +s.

As always recommended by search engines, widen your searches with "creative" queries, and keep trying.

If the engines don't work for your particular question, please just ask, we're sure someone will have an answer.  :)

Best regards,

Stu

[Mark Wey]

As this was my first year with this boat, I am still discovering things that I should have done earlier. One of them is changing the cooling system zinc on the M-35 engine. Here is what I learned. After consulting the manual and locating the fitting on the heat exchanger, I found the only access was from the aft cabin. On the 3” heat exchanger, it was on the bottom port side. I removed the zinc plug quite easily and noticed the zinc was completely gone. Another thing I noticed was that no water gushed out as I had expected. I pushed a small screwdriver up the hole, found the rest of the zinc, and started the water coming. It had not totally disappeared but just broke off in side the fitting. I had remembered to close the thru hull so there was only about 1 quart of water that was easily drained into a small container. The real problem came when I tried to clean all of the old zinc remnants out of the hole. I could not remove enough of it to insert the new zinc. Even if I could, I was wondering where the remnants would end up. The pieces that I did not manage to remove. Maybe in the impeller? Who knows?

Therefore, with this in mind, I then removed the end cap on the heat exchanger. It came off relatively easy. I was then able to do a through job of cleaning the old zinc remnants. Mind you, this work is all done by feel only. Direct visibility would have only been possible if I had removed the heat exchanger entirely. I used a screwdriver and a small pencil type wire brush to clean in the actual fitting and the inside of the heat exchanger. Care must be taken not to scar the threads too much.

What will I do different next time? One is to check the wear rate on a regular basis. Not to wait until it in such bad shape that I have extra work to do. Now that I know exactly what I am doing, it is only a ten-minute job. Besides while I am down there I can check the transmission oil level. Visually inspect hoses, clamps, motor mounts, the stuffing box and miscellaneous nuts and bolts.

As Ron says, do this project.

Mark

[captran]

I have found that I have to cut the zincs I get at West Marine as they are too long.  I have used a mirror to look into the side of the heat exchanger and use a shish kaa bob squewer (sorry about the spelling) to clear the tubes within the heat exchanger.  I also use an old squeeze syrup bottle to flush out old zinc material with water.  I only keep my boat in the water 11 weeks a year and have found that I only need to change it once a year.  My boat also has a "zinc saver" which I think is mounted in the aft port corner locker.  I don't know if that helps on my other zincs, nor do I understand how it works or if there is any maintainence on it.  I don't know if it came with the boat installed by Catalina or if it was installed by the prior owner.  but I guess "if it ain't broke"...

[Steve S.]

Mark,

Don't worry too much about the zinc remnants, they should flush out of the muffler through the riser.  The worst is that you may have some shards in the bottom of your riser.

Maybe its a Mark II issue, but I have never had a problem replacing the zincs in the 3 inch exchanger on my 25XP.  The 2 1/2" pencil zinc fits right in.  Now, if only getting the transmission oil out of the casing during commissioning were that easy.