MKII - "Best" Way to Change M35B Engine Zinc

[Joe Kern]

I changed my zinc this weekend.  I have done it many times and am frustrated each time as to how hard it is to get to.  I basically have to reach from the top front access and there is little room to get a wrench on it between hitting the side wall, throttle cables and metal bracket below it.  I have tried ratcheting wrenches, box wrenches and a socket driver but nothing can get in there easily.

So how do my MKII M35B brethren do it?  Am I missing an easy idea, tool or method?

If some of you remove the entire rear engine access can you let me know how you do that?  It appears there are corner braces on the aft port and starboard corners of the engine box.  Do you have to remove the braces on both sides in order to remove the starboard side panel?  Do you have to remove the lid or any screws in the bracket holding the lid?  It seems like a lot of work to change the zinc every few months, but probably better than the frustration I have been fighting.

Joe

[rirvine]

I feel your pain.   The screws that hold the rear of the engine box together are all inside the box –  four at each corner.   When I had the rear of my engine box off to clean out the heat exchanged, I put a door (as large as possible) in the starboard side of the box and put all the screws in from the outside of the box – to make them easy to get to next time.

Now to change the zinc, open the door and there it is.

Ray

[Stu Jackson]

Have you seen this?  --  http://c34.org/bbs/index.php?topic=3222.0  with other links to other posts.

[Joe Kern]

I did.  I was hoping for some new ideas or some pictures of the access doors.  Ray, if you get a chance to take a picture of your design I would appreciate seeing it.  I guess one of these days I will need to take off the rear engine box just to see how it comes apart  and (hopefully) goes back together.

Joe

[sail4dale]

the box is easy once you get the eight screws off.  It;s just a pain to work in the back getting all the cushions and gear out of the way.

When it's off you have great access.

[Stu Jackson]

Another source is Jon Schneider's great Knowledgebase.

I did a search (Ctrl-f) on the word zinc, and came up with this: http://www.c34.org/mainsheet/pdf/1100.pdf

It just so happens to be the FIRST "hit" on a search on the Knowledgebase on that word.

It's called: "Accessing a Heat Exchanger Zinc on a Mark II."

It's in the November 2000 Mainsheet magazine Tech Notes, right here on our website, and was contributed six and a half years ago.  Thanks to Marc & Cam Rivard First Light #1497 for posting that idea.

It also has a picture of the installation.

[reedbr]

I assume we are talking about the HX zinc.  My MkII is a '97 and something must be different on mine as I don't have any problems.  I have to do it by feel, as I can look at it or put a wrench on it, but not both.  I change mine once a year with the Racror fuel filter.  I come up from the bottom, and my zinc bolt is on the underside of the HX. I've already got the cushions and berth support panels out for the fuel filter change so I just reach over with a regular socket wrench and spin the old one out and a new one in.  I haven't found short zinc's so I always have to cut a long one down.  I measure the correct depth with a pencil, putting the eraser end in first.  From what I remember, the handle of the socket wrench clears the underside of the vertical wood cover when I'm wrenching it.  What changed on your (I think newer) boat?   

[Jeff_McKinney]

I find the zincs often disintegrate at the mid-point and break off, leaving a big chunk plus some smaller bits in the HX. This means pulling the end plate to clean it out. I'm not as skilled as Ray with woodwork so came up with a relatively painless approach.

I use the following steps to get optimal access:
1. Pull the mattress cushions and drive train cover board and set them up forward. The board needs to come out as there is a stringer attached to the lower edge of the cabinet that will make removing the cover impossible unless you do this first.

2. Take out the screws holding the rear cover in place.
NOTE: After removing the screws holding the housing to the hull I found that one long screw in each forward corner of the rear engine cover (where it butts up against the fiberglass forming the front wall of the cabin) and one shorter one in the port rear corner against the port side bulkhead is enough. The friction fit along the fiberglass on the starboard side is not bad, but a bit of judicious sanding followed by a coat of urethane varnish on the cabinet edge helps make removal easier.

3. Remove the rear engine cover cabinet by lifting and rotating counter-clockwise about 15-20 degrees. It should free up easily so you can then lift and slide it to port/aft out of the way. You do NOT need to remove the lid.

All of this adds about 10-15 minutes total to the job, but prevents the damage to the hands, the contortions experienced by Joe, and an opportunity to use the special words.

Now I have a clean shot at the stuffing box, raw water strainer, Racor, transmission fill and drain plugs, the little filter on the fuel lift pump, the HX and zinc, etc. Makes all that periodic maintenance a LOT easier.