heat ex changer flush question

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magna 6882

Apr 20, 2020
Vessel Name
Vessel Make
North Pacific/ NP-45 Hull 10
Mt transmission cooler has some growth on it and i was going to make a flush kit and run barnical buster through it. I got to looking at it and am wondering if i should just flush all three at the same time. the charge air,transmision and engine heat are in a row. Seems like i can connect to the inlet of the charge air and the return to exhaust and flush the whole business. Thoughts?


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Remove the zinc. Run a 22 cal. Rifle brush through it. I would do each one individually with visual inspection.
Yes, you can flush them all together. I use to just run BB in and let it sit for about 6 hours then start the engines and flush it out since the impellers wer really difficult to get out.
Engine raw water cooling parts do require periodic FULL off engine servicing. Barnacle Buster will not fully meet the system's needs. For example: if your engine has an aftercooler, the air side of this "heat exchanger" will eventually clog up with oily deposits restricting air intake. BB will not do anything for this condition!
Also, the various components should be disassembled, cleaned, new seals or O rings installed, and then be pressure tested to ensure that there are no leaks from one side of the exchanger to the other. Corrosion can lead to leaks, and you don't want sea water in your oil, transmission fluid, fuel, coolant, or going in the air intake. Very expensive repairs or replacements could result. BB is really a temporary help to address part of the need, maybe a mid season use to allow for an extension of time to do a full service in the fall?
Depending on several factors like local salinity, growth, etc. this full service should occur every 4-6 years. See sbmar.com for more info from Tony Athens, a marine diesel guru (under Tony's tips or on his forums).
I had to open the charge air inlet end to remove a zinc that came loose. The design puzzles me. There seems to be divider between the upper half. I would think that would allow water to flow through the upper half and not so much on the lower half. Am i missing something?


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110% agree on the full cooling service. From what I see you need a full tear down cleaning. Add freshwater flushing if you can goes a long way to preventing this.

I zoomed in on the pictures and you can see the corrosion creeping around you o ring seal. Once water does it is on the air side and there goes another engine due to poor cooling servicing.
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I had to open the charge air inlet end to remove a zinc that came loose. The design puzzles me. There seems to be divider between the upper half. I would think that would allow water to flow through the upper half and not so much on the lower half. Am i missing something?
This is a 2x bypass cooler. that is the reason for the separation. Water flows through the bottom 1/2 first, returns through the upper 1/2 before going to the engine. If you look at the other end you will see no separation.
This is what we did:

I'm a fan of rodding out heat exchangers. My tool of choice is solid copper wire sold at Home Depot or Lowes. You can buy it by the foot off the big wire rack. It's soft, so safe on the tubes. It's available in several sizes. Basically you want it squared off on the end, not tapered to a point. Being soft and bendable, it allows you to use a smaller size to get the outer tubes on the OP's original picture.

While Barnacle Buster will work, it requires flow through the tubes. So tubes that are completely blocked won't be reopened.

Aftercoolers (as pictured), rely on a good "mating" surfaces and a functional O ring to keep water out of your engine air intake. Due to the nature of this operating environment, (dissimilar metals in saltwater...... somewhat like a lead acid battery), corrosion will occur at this interface possibly resulting in water intrusion, or a pitted mating surface, or sometimes a virtual "welding" of the parts, requiring an expensive replacement of the aftercooler (or core), and in the worst case situation an engine "rebuild".
Frequent "off engine" maintenance of aftercoolers (every 3-5 years) is highly recommended and can be done by a DYIer. I did my own using instructions and info from sbmar.com. Don't wait too long as the ongoing corrosion (even when not running) can do a lot of unseen (until trying to disassemble) damage.
BB and even rodding will not solve these issues. However, it is your boat and your dollars :) Good luck!
My boat is 26 years old and I believe that the aftercoolers had never been serviced, I took them off and couldn’t get the cores out. I bought one new aftercooler. Then took the old one to a machine shop to press out the core. It took 13 tons of pressure to get the core out. I bought a new core for that aftercooler. I also followed Tonys procedure to service the new cooler and also the one with the new core. The cores had quite a bit of white corrosion on the lower end and somewhat less on the top of the cores. I agree that regular servicing is indeed needed.
Got the fresh water flush T installed. I only took a picture of the T. I ran the line 25 ft out to the back of the boat for exterior connection .


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FW flushing should allow increasing the interval between required cooling system services, and help keep your engine running cooler. However, still service the aftercooler every 3-5 years and don't ignore the rest either (other components and a coolant change/flush). JMHO.
My main thought is we are able to use the boat in the summer since we travel in the motorhome and also have a home in palm springs for the winter cold months. Our boat can sit for several months without running. I dont think i will flush after every run during the summer but if i am figuring on leaving it sit a bit due to travel it would be could to be sitting with fresh water in the cooling system.
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