hx zinc acces on Mark II boats

[canuck]

2004 C34 MK2 hull 1678
We have a very annoying problem and would apprecate any feedback. The Admiral and I are in Point Roberts Marina, Washington (Pacific North West) - a "hot" marina.
We purchased the boat new and have been in the same slip with the samer neighbours since May 2004. We assume our galvanic isolator is working and we just replaced the two prop shaft zincs on Sept 3, 2006. (I have found that these need to be replaced every 6 months.) We run our fridge year round because it is also our floating cottage. I am checking the HX zinc monthly and in the last 6 months I am finding that upon removal, the zinc anode has disinegrated around the thread area at the top of the 9/16" nut. When I remove the nut, the inside of the nut has the remains of the threaded portion and the pencil portion remains in the HX. This happened today when I checked the zinc which I installed on August 30, 2006. I use the OEM pencil anode. The new anode would not screw in properly so I removed the end cap. I found the remains of 3 of the anodes. All were in good condition but all had suffered the same malady.Separation at the thread portion.
I called Gallery Marine but they could not determine the cause other than the level of the water in the HX might happen to drop down to the same height as the nut/zinc when the boat is tied up. The intake valve is closed while at the dock. Any ideas or suggestions as to why is this is happening?

In order to check the #$% zinc we have to clear out the aft cabin including the mattresses. This does not make the Admiral happy. To alleviate this annoying task I plan on instaling an access door in the rear engine compartment. Why Catalina did not do this is a mystery. They have a door to access the fuel filter but we are spending a lot more time in the zinc/end cap area. It looks like I will use the intake valve access door and replace it with a West Marine product. I called Catalina today and was quoted $400 for a Catalina part!! I thought Harley Davidson was bad!
Has anyone done ant modifications to make this zinx inspection task easier?

[Tom Soko]

Canuck,
It could be that your pencil zinc is too long, and is bumping into the innards of the HX when it is screwed in.  I'm not sure about which models have which HX, but in a conversation with a Westerbeke/Universal rep at a boatshow, they suggested cutting 3/4" off a standard pencil zinc to make it fit better.  They said it was not cost effective to manufacture a special pencil zinc for just one engine model.  I've been doing that for years, and the zinc always comes out with the plug/cap.  Just a thought.

[Stu Jackson]

Good idea about the access door.  On our MarkI I can reach over the engine and get to the zinc from the front, never tried it on a Mark II.

I did a search on zincs, and found this one: http://c34.org/bbs/index.php?topic=2593.0  There are many, many more, since this is a recurring subject, so you may want to try a search and see if anything elese strikes a chord with you and your experience. 

Based on this thread reference, seems like Tom might be onto something about the length of the zinc, since others have mentioned it before.

[Ron Hill]

Can : Over the years I written a number of responses to Zn questions in the Mainsheet, FAQ's and on the message board.  In all of them I'd advised that when you replace the Zn to take a #2 pencil and put in the hole and make sure that the full length will fit!!  It depends on the HX and how the "innards" are aligned.  Some of us have to cut ours off and some don't.  The #2 pencil will let you know and how much you have to cut off. 
I've also found that it's prudent to bevel the edges of the Zn before inserting!!   

[John Sheehan]

On our Mark II I have been able to access the HE zinc by removing the upper ladder (stairs) and after propping the hatch open I can reach the zinc using a 9/16" box wrench from the main cabin.  I am not at home now so am unable to tell you what length the zinc is.  Ron's suggestion with the pencil should work fine for getting the size. I have been changing the zinc every 3 months or so with no problems other than the residue from the disintegrated zincs partially blocking the flow in the HE after a few years.

[John Langford]

Repeating a suggestion that an elctronics engineer (and Cat 40 owner) passed on to me: screw a soft metal (iron) bolt the same length as the zinc into the bronze/brass zinc holder. He argues that the normal zinc pencils erode largely because of the passage of water over them; not because there is an electrolysis problem. Any electrolysis problem will be dealt with by the lack of nobility of the "iron" zinc. It has worked for me so far.

[Ron Hill]

John : I've heard this theory professed before.  As long as the the price of a pencil Zn is under $5, I'll continue to use them instead of a soft iron bolt.
BTW, my shaft and prop are are in a flexible coupling.  This means they are isolated (electrically) from the engine.  I reuse my shaft Zn year after year, as it has minimal erosion!!  Alot of water flows by that shaft Zn !!   

[Stu Jackson]

Canuck

H&L Marine makes the doors for Catalina.  You can purchase doors, etc. from them or from West Marine.  The hinges can be purchased a lot less expensively at a hardware store.  It would be great if you could take some pictures and write up what you do for publication either here, in Projects or Tech Notes in Mainsheet magazine.