Mike, same thing happened to me last year 'cuz I forgot to check on it based on my engine log schedule. I had an excuse: I broke my leg skiing.

I took the HX off to dig the pieces out. You just don't wanna have stray pieces of zinc floating around inside the HX, even though I agree with your assessment of the flow directions.

It's not really that hard a deal to do, and is good to check every once in a while anyway. Mine comes off every two years or so. The intake port from the rw pump is where a lot of salt drops out, so check the ports carefully.

I also noticed some rubbing on the bottom of the shell where it met the bracket at the end of the engine. I cut up a bicycle rubber inner tube and installed it between the shell and the bracket. We have an M25 where the HX is held on by large hose clamps. Some other newer HXs and engines come with brackets welded onto the HX for mounting on the engine, just a different design.

I would NOT have known about this without removing the HX. Woulda been a catastrophic failure, coulda lost the engine from overheating. A few hours of work is worth checking carefully.

My boat, my choice.

You can save the antifreeze before you remove the HX, this way, see reply #6: [url]http://c34.org/bbs/index.php/topic,4518.0.html[/url]

Sounds like you have an M25XP engine.

I don't know how easy it is to reach the HX on the C36. To fish out the lost zinc all that is necessary is to take off the end cap. Reinstall the end cap with a new gasket and o ring. Gaskets and o rings are available from Sendure, or you can make you own from rubber gasket material and pick up a new o ring at Ace/Lowes.

I agree with all above. A good HX cleaning and inspection every couple years is excellent preventative maintenance. The model engine really doesn't matter, Stu's save the antifreeze method can be applied to almost any engine.

I have been contemplating the idea of removing and cleaning out my heat exchanger. I too have had one of the pencil zincs break off and it is inside of the HX. I have searched available threads on this topic and can't seem to locate any procedural steps in removing it. Can somone outline the steps, precautions and tips? Thanks in advance.

It's relatively easy to open up one or both ends of the heat exchanger on the M35B. Make sure you have new gaskets, O-rings and zincs standing by, as after the HX is open is no time to be driving around looking for parts. Remember to note, when the end cap comes off, whether the O-ring is outside of the gasket or inside of it. (I seem to recall that it is outside the gasket.)

Most of the time when you buy a fresh zinc it is too long. If you try to screw a too-long zinc into the HX it will break the zinc and might even damage the HX. Figure out what length you need and simply hacksaw it to the proper length.

If you open the stbd end cap of the HX (the zinc end) you can stick your finger in there and feel for the zinc debris and pull it out with your finger.

If you remove both end caps and put a flashlight at one end, you should be able to look through the full length of the HX. I suppose you could get a long-handled brush, like a bottle brush, and just push the debris from one end out through the opposite end. To control where the debris goes, I would push from port to starboard though.

Thanks Larry.

I had the same problem - broken zinc. I can feel the mostley intact lenght of the zink laying inside the stbd end of the HX - but I can not remove it from nut hole. Why not place another water strainer before the raw water reaches the raw water pump. Anyone see any problem there? I have a M35B. I was unable to remove the two bolts holding the welded brackets to the engine.

[QUOTE=baysailor2000;6631]Why not place another water strainer before the raw water reaches the raw water pump. Anyone see any problem there? [/QUOTE]

Because the flow is:

inlet thru hull
strainer
raw water pump
HX
muffler
overboard

You already have a strainer, what would another one do to help the issue of the zinc inside the HX?

I have had an issue with overheating this summer. Just recently I decided to check the heat exchanger and like others have said, there was a fair amount of zinc debris on that end. I tried to pick it out but was not easy and there still seemed to be a fair amount in the bottom of the HX. I took my inflatable pump and used that to blow out the end ...worked real well! Just a tip for those that want to save some time.

PS hold the nozzle down and do not blow straight into the HX so as to avoid blowing particles into the tubes. Also note a length of .032" SS wire can be used to clean out the tubes or check for caught debris.

Another similar problem can occur that happened to me the first time I changed my hx zinc: The zinc separated from the nut but stayed in the hole. Try as I might, I couldn't get it out. So what I did was get a short length of copper tubing of the right size and tapped out the inside of it to match the zinc. I threaded it onto the zinc. Since the outside diameter was less than that of the nut, I didn't have to thread it into the hx so all I had to do was grip it with a pair of channel locks and pull it out.

I thought somebody might have this problem in the future and might make use of my solution.

In the world of keeping it simple...
I use a wet/dry vacuum to suck out the zinc end of the HE with the cap removed. If feeing more energetic (getting rarer these days) I pop the opposite end cap and rod out the HE tubes with a length of 10 gage bare copper wire (12 gage will also work). Then I use the vac to clean out both ends of the HE. We keep a 2 gallon 120v Wet/Dry vac on Tara for cabin cleaning and keeping the bilges dry after heavy rains. Seems to work...