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Go Back   SailNet Community > On Board > Gear & Maintenance
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  #1  
Old 01-01-2009
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Heat Exchangers - Up Close & Exposed

When we bought this 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):


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):


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:


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, use a good trouble shooting methodology to make sure it's not a blocked HX.:


This is the end I call the trouble end. With Universal/Westerbeke HX's the zinc is almost he 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.

#2 The zinc 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 whole thing 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.

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 probably in different areas with different water 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.:



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 $20.00-$30.00 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.
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Last edited by Maine Sail; 01-02-2009 at 11:02 AM.
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Old 01-01-2009
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Nicely done. Its great to see a good explaination of how things work, even when you know how they work.
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Old 01-01-2009
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thanks

Wow, Mainesail, thanks again for another superior, pictorial, and tutorial post.
Such a totally relevant (to me anyway) post. I have an '87 WB 21A with a leaking (building crystalized crud on outside) end cap and Ive been wondering what was in store for me when I pulled it off. Now I know. How about taking your WB apart piece by piece so I know about everything, just kiddin well, sort of.
Does pulling the HX automatically mean that you will replace all the hoses just to be sure or can I expect to get them off intact?? (of course, it all depends, right?)
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Old 01-01-2009
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Hats off MaineSail, as usual. I hope you can add some of the above text to your own projects page although the pictures there already tell most of the story. This easily could be nominated for a 'sticky'.
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Old 01-01-2009
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Originally Posted by scosch View Post
replace all the hoses just to be sure or can I expect to get them off intact?? (of course, it all depends, right?)
Yes replace!!!!

For more on taking apart a Westerbeke see these two posts:

Gotta Love Boats..??? (LINK)


Gotta Love Boats..??? Part 2 (LINK)


P.S. When it comes time for a re-build (probably not for a while) I will photograph it..
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Old 01-02-2009
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Just got back from the radiator shop..

Just got back from the radiator shop and I'm glad I went. I got a whole lesson about why DEX-COOL is not a good idea. Unfortunately my 2003 Westerbeke came from the factory with DEX-COOL and has been changed regularly but it was not enough to prevent some rusty looking sludge in the HX fresh water side. Now I will also need to flush my engine and convert it to regular antifreeze. Sometimes newer is not always better..?

DEX-COOL Class Action (LINK)

DEX-COOL Class Action (LINK)

It's really good to still live in a city where we actually still have a few specialty shops. There are not too many specialists left especially good old fashioned radiator shops who actually know their trade and take it very seriously.

So here's what I'll get for between $32.00 and $44.00..

1) Manual reaming of the copper tubes with special brushes.

2) A full 12 hour+ soak in "boil out compound" which you need to be licensed and certified to use.

3) A high pressure circulation flush, for up to three hours, with a another cleaner.

4) A neutralizing bath which, neutralizes the acids used in cleaning & brings the HX back to a neutral PH. The liquid starts out green but turns to red when it is neutral so you know it's done.

5) A complete pressure test at 60 PSI for 6 hours.

6) A full sand blasting of the entire heat exchanger!! He will make it ready for paint. To do this step alone would take me an hour or more and I make a more $$ per hour than the high side of this estimate. My time is money and Paul can do it for less...

Why go anywhere other than a professional for this?? I would gladly pay more for this level of service but I don't have too. Even at $150.00 it seems worth it..

Paul also agreed to come out in the spring and do a full engine flush and conversion back to green antifreeze..
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Old 01-02-2009
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Nice deal for you Maine...unbelievable really. Nice post too...thanks!
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Old 01-03-2009
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That's great information, Maine (I keep wanting to call you H.!). I will be taking off my old Westerbeke HX (off a W-52 and quite large and rectangular), and cleaning and rebuilding it before we go and then stowing it as a spare. I will have a new one installed when I rebuild the engine, but it's good to know the zinc facts and the general way in which it works.
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Old 01-03-2009
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Incredible Post! Thanks.

One small note. On our W33, the surveyor noticed that there was some water leakage at the HX. The report states: "...it was unclear whether leak was coming from hose connection or from thru-corrosion on heat exchanger". She told me that there could also be an overpressure situation.

After the sale, when I did a close inspection, I saw that the endcaps had hairline cracks because the PO had torqued them down too tight. The leak only showed up when the HX was under pressure. I replaced the o-ring with a live rubber o-ring and the leak stopped for good.

Moral of the story - don't torque these thin bronze plates and use new o rings!
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Old 01-03-2009
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Originally Posted by Sabreman View Post
One small note. On our W33, the surveyor noticed that there was some water leakage at the HX. The report states: "...it was unclear whether leak was coming from hose connection or from thru-corrosion on heat exchanger". She told me that there could also be an overpressure situation.

After the sale, when I did a close inspection, I saw that the endcaps had hairline cracks because the PO had torqued them down too tight. The leak only showed up when the HX was under pressure. I replaced the o-ring with a live rubber o-ring and the leak stopped for good.

Moral of the story - don't torque these thin bronze plates and use new o rings!
Good point! You do not want to over torque these plates as it could damage the rubber gaskets and distort the o-rings. They require very little torque to remain leak free..
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