Servicing heat exchanger

[Rortega46]

I haven't done maintenance on the heat exchanger since buying the C34 four years ago.   Yesterday I removed the end-cap from the HX inlet side to inspect the heat exchanger's condition. The good news is there was little to no debris inside the HX and the tubes look to be in good shape.  I had a few issues [see below] and would appreciate comments for future reference.

Before removing the end-cap, I closed the raw water inlet thru hull. After removing the endcap, I assumed raw water would leak into the bilge and stop fairly quickly after some drainage.  Well, raw water just continued to drain...drain...drain, and never did stop running onto the floor and into the bilge.

After cleaning and replacing the gasket, o ring and end-cap there was no raw water flowing through the system.  After removing a small amount of debris in the thru hull and replacing the gasket on the raw water pump [which appeared to be incorrectly installed], raw water began flowing again.  I'm not sure if these things were enough to obstruct the raw water flow.

While installing a PSS dripless seal 3 years ago, the yard removed the zinc from the HX and ran the water from the PSS to where the zinc was previously.  They said you are primarily in fresh water so no need for the zinc.  I only figured this out a year after it was done, but it's always bothered me.

*Why did the raw water not stop draining when the HX end-cap was removed?
*Is there a need to prime the raw water pump after removing the HX end-cap?
*Maybe I oversimplified the HX servicing process.  Step-by-step procedures would be helpful. 
*Should there be Permatex or something else applied to the gasket?
*Should I remove the other end-cap to inspect and clean, or not worry about it since the inlet side looked good?
*Is HX servicing an annual maintenance process to be done?
*Should I look at re-installing the HX zinc next year when doing a haul out and bottom job?

Thanks in advance for your replies and comments.

[Stu Jackson]

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1  Why did the raw water not stop draining when the HX end-cap was removed?
2  Is there a need to prime the raw water pump after removing the HX end-cap?
3  Maybe I oversimplified the HX servicing process.  Step-by-step procedures would be helpful. 
4  Should there be Permatex or something else applied to the gasket?
5  Should I remove the other end-cap to inspect and clean, or not worry about it since the inlet side looked good?
6  Is HX servicing an annual maintenance process to be done?
7  Should I look at re-installing the HX zinc next year when doing a haul out and bottom job?

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Randy,

1  No idea why, but you did say "...After removing a small amount of debris in the thru hull..."  Could be it wasn't really closed.

2   No, the rw pump is below the waterline.

3   I have been recommending that HX be removed for servicing for many, many years now.  It is rare that tubes get blocked, although it has been reported.  The reason is that the tubes are narrow and if the boat is actually used they should clean themselves with the high velocity water running thru them.  What often happens is that the inlet port gets blocked if you're in salt water because the salt precipitates out when it first hits the HX.  Your boat, your choice. 

4   Not necessarily.  Plain gasket is fine on the HX, and pump flange to engine and faceplate to pump.

5   See #2 above.

6   See #2 above.  Every two or three years.

7   Absolutely.   Why wait?  The PSS hose has a different purpose and was never intended to do that via the HX.  It was a bad idea to begin with.  The zinc protects the HX.

[Craig Illman]

1. Because your PSS is below the water line. When it's connected to the HX it will find it's way to the raw water pump. When a PO installed a PSS, they ran to vent to a T on one of the raw water hoses below the water line and it had the same behavior.  Look at the last frame in this article  https://pbase.com/mainecruising/pss_shaft_seal&page=2

[Ron Hill]

Ramdy : You may want to look at a fresh water anode rather than a Zn!!
   
The internal engine coolant flows thur the tubing inside the HX and the raw water flows around the outside of that tubing to cool it down. If you took off the end cap by the anode hole than most all of any debris should have been right there.  After a few more years it might be good to take off the HX and have it cleaned by a Radiator Shop.

I used to run "Lime-a-Way" thru my HX to dissolve any minerals.

A few thoughts 

[Rortega46]

Thanks for your replies.  I'll work on re-routing the PSS hose so a zinc anode can be added to the HX.  Using a Taco model 400 Haven't looks to be a good option for the PSS hose. Thereafter, removing the HX for servicing can be one, but not this year.

[Roland Gendreau]

Randy
One of my winter projects was to remove the HX and get it serviced.  It had not been done since I purchased the boat 14 years ago. In the process, I replaced the engine antifreeze hoses.
I found the internal tubes looked relatively clean with some deposits.  The 2 brackets securing the HX to the transmission were both separated from the HX and needed to be re-brazed.  I brought the HX and the new gaskets and o rings (from Catalina Direct) to a radiator shop to clean it out, pressure test it and to get the brackets properly brazed back on. They found a pin hole leak on one of the raw water nipples, which they also fixed.

Once I got it back, I primed and spray painted it, and reinstalled it with new anti freeze.   It was a good maintenance project.

[Stu Jackson]

More HX photos from the 101 Topics:

Heat Exchangers 101:  Sources for replacement  Good Guys at Sendure

http://c34.org/bbs/index.php/topic,6920.0.html

[Roc]

Randy
I routed the hose for the PSS seal so the end is above the water line.  I believe PYI suggests that now.  You can route it into the area under the head sink then to to the lazarette on the port side.  Secure the hose along the way and put the end as high as possible.

[DaveBMusik]

Randy
I routed the hose for the PSS seal so the end is above the water line.  I believe PYI suggests that now.  You can route it into the area under the head sink then to to the lazarette on the port side.  Secure the hose along the way and put the end as high as possible.

I put mine under the head sink but also put a Taco vent on the end so no overflow
https://www.homedepot.com/p/1-8-in-Hy-Vent-400-4/202312925

[Rortega46]

Roc
Where and how did you end the hose?  Is it near any other holes in the hull?

Roland
Sounds like you did a process and it turned out great, and I'll need to do it in the future.  Just, not this year.

Craig:
That explains a lot..

Thanks

[Roc]

Randy,
The hose bends to port through a hole I drilled in the area on the picture where the red circle is shown (this is an old picture before this was done).  From there, you are in the area of the sink vanity.  The hose then runs up into the forward most section of the port lazarette.  I also had to drill a hole in that section.  Then the hose ends as high as possible at the top part of the lazarette, in the upper most/forward corner.  That is far above the water line.  The hose is well secured along the way, and at the open end, to make sure it won't move.

[Ron Hill]

Guys : If you are servicing your HX and want new seals and end caps go to Glen Mar Marine (800) 282-0123 for your parts.
I'm sure they are cheaper than Catalina Direct and the parts are genuine Sem-dure.   

Wrote this up in the Mainsheet Tech notes way back when!!

A thought