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Heat Exchangers - Up Close & Exposed

Maine Sail

Member III
I posted this elsewhere but thought you guys might like it too with all the Universal engines in Ericson's...

When we bought our boat two years ago one of the things on my list was to remove and clean the heat exchanger (HX from here on). Now that my bell housing is cracked I had a good opportunity to attack this and take photos of the process.

HX's are one of those things that many boaters find mysterious but they are in fact quite simple and easy to work on, especially the cylindrical type as used on Universal and Westerbeke engines. A marine HX is very much like a cars radiator. Rather than cooling the engine antifreeze with air passing across aluminum fins, the marine HX uses raw ocean or lake water run through copper tubes. This raw water is doing, and serving, the same purpose as the air does on an auto radiator.

This is the basic anatomy of a HX. There are two sealed water loops or circuits in this tube, a fresh water side (engine antifreeze), and a raw water side (lake or ocean water):
107682452.jpg


To see inside simply remove this bolt and pull the cover plate off (this can usually be done on board if you have access and a closed seacock):
107682459.jpg


What's behind the cover plate? On this type of HX all that's there is an o-ring and rubber gasket. Be sure to have new replacements on hand before removal:
107682462.jpg


This is the most confusing part trust me! The in-coming raw water passes into quadrant #1 and makes pass #1. When it hits the end of the tube it makes a 180 degree turn and comes back for pass #2. It then hits the end of the tube again and is forced back though the HX for pass #3 where this process happens again and the raw water is finally sent out of the HX and into the wet exhaust system. In essence the raw water passes through four quadrants or quarters of the HX before leaving the HX. If you look closely you can see some eel grass and an old impeller vane. This first pass only consists of a few small diameter copper tubes so it's important to monitor temp and on an abnormal rise to use a good trouble shooting methodology and make sure it's not a blocked HX.:
107682465.jpg


This is the end I call the trouble end and it is the one I clean most often, thought eh other end can be bad too. With Universal/Westerbeke HX's the pencil zinc is almost the same width as the threads for the head. Zincs do funny things when they sacrifice themselves one of them being that they begin to flake and appear to get bigger in diameter. If the zincs are not changed often enough a few things can happen as did here.

#1 the zinc gets thin and the water pressure snaps it off the head where it remains until you remove the cap and clean it out.

#2 The zinc deteriorates, crumbles and flakes off inside the HX which can lead to plugged tubes.

#3 The zinc gets too fat and when you un-thread it the pencil zinc snaps off the head. People often assume the zinc was totally eaten but more often than not it just broke off because it went too long before being changed.

The zinc in the photo, which came out in one piece, was about eight weeks old. I change them about once every 8 weeks. The PO spent time cruising and was in many different areas, with different water/electrolysis issues, so getting to know his zinc schedule was probably tough, hence the crud. I should have pulled the cap a long time ago but my temps were running spot on. If you don't get a full zinc out it's a good idea to pull the cap and retrieve the pieces.:

107682802.jpg


Tomorrow I drop it off at the radiator shop for a cleaning then clean it up and paint it. I learned a long time ago that paying the $30.00-$45.00 for an HX cleaning is soooooo worth it. Hell I can't even buy the Rydlyme, to DIY, for what my local radiator shop charges.
 

Frank G

Member II
Hello Main Sail,
I would call you by name, but it's not posted.
Thanks a bunch for his great, timely piece. I currently have my engine drained as I'm working on installing a new alternator bracket, and changing out my thermostat, installing a new exhaust pipe and was planning on insalling a new zinc anyway. I'll remove the end cap and see what is in there. I would assume that you can get the new gaskets from Torrenson.
I have been trying to order parts from them since last week. someone finally left a message that they were closed until Jan 5
Thanks again, and have a great year
Frank
 

Maine Sail

Member III
Everyone

Everyone seems closed my local Westerbeke/Universal dist is closed as is Westerbeke headquarters as is Torenson's. Don't forget the o-rings that go with the gaskets..
 

Frank G

Member II
Hi again main sail
You have some really good photo galleries on your website.
thanks for the link
Frank
 

Sven

Seglare
If you don't get a full zinc out it's a good idea to pull the cap and retrieve the pieces.

Good suggestion. I wonder if that is why the zinc in our exchanger has to be cut down to size ... there are old zincs in there ? Something else to investigate.

Thanks,


-Sven
 

Starduff

Member II
Heat Exchangers

Having addressed the Zinc pencil in the heat exchanger, I was wondering if someone kowledgeable (as there are many on this site) might speak to the use of Magnesium pencils in fresh water. How important or not it is, etc.

Richard
E-28, Hull 651
Polonius
 

Brian K

Member III
I sail in freshwater only and use magnesium anodes on the prop shaft but have never been able to locate a magnesium anode for the engine. I've been using the only thing I can find - zinc. If there is a source for magnesium pencil anodes please let us know. Thanks!
 

Starduff

Member II
Heat Exchanger

Hi Brian,

I use a zinc pencil also. I will look into whether there are magnesium pencils or not. Never thought to ask before this thread.
I faintly recall an article or conversation where someone stated the Magnesium annodes didn't make much difference. So, I haven't been using one the past two years since my boat moved from Long Island sound to the mid Hudson River fresh water, and haven't seen any change. Your thoughts? Or other for that matter? I am trying to clear my confusion on this issue.

Richard
 
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WBurgner

Member III
Great Thread

Great job, Maine Sail. The pictures would have have been wonderful to have five years ago when I had to tackle the same project.
 

u079721

Contributing Partner
Home made HX gaskets

Great job here. My one suggestion is that those gaskets can get pretty darn expensive if you are opening up the ends all the time. I can't remember what I paid, but the price did seem outrageous ($10 each?) at the time.

But the gaskets are really nothing special, and I used to just make them myself from a sheet of thin gasket material that I bought from McMaster Carr. Even rubber inner tube material will work in a pinch.

As for the length of the pencil zincs - not being able to get the full length in is very normal, and does not mean you have crude in there. Though of course it would be a good idea to remove the end piece at least once to check.
 
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Frank Langer

1984 Ericson 30+, Nanaimo, BC
Assuming regular maintenance on the impellor (ie. no broken off vanes, etc.) and zinc replacement, and normal flow out of the exhaust with no sign of engine overheating, how often would you normally take the heat exchanger apart for checking/maintenance?

The universal engine operator's manual doesn't mention this as a normal annual maintenance item, and I don't hear people on our docks talking about doing that (like they do about changing oil or replacing zincs). I don't want to take things apart unnecessarily, but also don't want to neglect an important item either.

Any thoughts?

Frank
 

Starduff

Member II
Heat Exchangers

I sail in freshwater only and use magnesium anodes on the prop shaft but have never been able to locate a magnesium anode for the engine. I've been using the only thing I can find - zinc. If there is a source for magnesium pencil anodes please let us know. Thanks!

Brian,

It seems there is a source for magnesium (and also aluminum) pencils for fresh water use. Although there is also concern about their ability to break and ubstruct the heat exchanger. Here is a copy of an email I received from Bob Olsen at BoatZincs.com.

Richard

Zinc anodes tend to passivate in freshwater because they are unable to slough off their oxides. Aluminum and magnesium anodes do a much better job.

The major concern about aluminum and magnesium pencil anodes is their physical strength. The manufacturers I’ve spoken with to say there are valid concerns about aluminum and magnesium anodes breaking off within the heat exchanger and causing restrictions in water flow.

Call if you have questions.

Best regards,

Bob Olsen

sales@BoatZincs.com
978-841-9978
 

Starduff

Member II
Heat Exchanger Maintenance

Assuming regular maintenance on the impellor (ie. no broken off vanes, etc.) and zinc replacement, and normal flow out of the exhaust with no sign of engine overheating, how often would you normally take the heat exchanger apart for checking/maintenance?

The universal engine operator's manual doesn't mention this as a normal annual maintenance item, and I don't hear people on our docks talking about doing that (like they do about changing oil or replacing zincs). I don't want to take things apart unnecessarily, but also don't want to neglect an important item either.

Any thoughts?

Frank

Frank,
I checked my manual on the Universal motors. The maintenance check list suggests cleaning the Heat Exchanger every 500 hrs.
Richard
 
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