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Hi all, I've got my heat exchanger, aftercooler and oil cooler out for a much-needed deep cleaning in an ultrasonically-invigorated bath. While cleaning up the engine, I came across this little doodad that certainly looks like it wants to be a cooler, but it's much smaller. Please look at the attached picture and let me know if this is yet another oily mess waiting for me to take apart and clean.

Thanks!

Steve

Kallisto 5369

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Posted by: Steve Covington on 6/20/2026 at 4:02 PM
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Hi all, I've got my heat exchanger, aftercooler and oil cooler out for a much-needed deep cleaning in an ultrasonically-invigorated bath. While cleaning up the engine, I came across this little doodad that certainly looks like it wants to be a cooler, but it's much smaller. Please look at the attached picture and let me know if this is yet another oily mess waiting for me to take apart and clean.

Thanks!

Steve
Kallisto 5369

Attachment(s):
File: 20260620_165406.jpg (1.8 MB) -- Address: https://images.clubexpress.com/849970/attach/4429461_0_20260620_165406.jpg



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Steve,

Where does that blue hose go to? Maybe a stabilizer oil heat exchanger. But yes, you should have that cleaned and pressure tested when you do the other coolers.

Richard Nye

Untethered, 57-22

https://forecast.predictwind.com/tracking/display/MV_Untethered/

That’s your gear oil cooler.

horribly mounted behind the aftercooler. Ended up just replacing mine to buy the peace of mind of not having to access it beside the zinc for awhile.

I’ve heard of relocation kits to make it more accessible. But never found the exact one that came with the right hoses.

-Rick

5351

Steve, that looks similar to QSB 5.9. As I mentioned to you I vacuumed and rodded mine out “in place was too overwhelmed we removing both of those too. Plus I permanently removed one fuel cooler and will get the other one later. Such a pain taking off the coolers on the smushed against fuel tank side of the twins.

Corey
Sent from my iPhone

My thanks to everyone who told me what I already innately knew but didn't want to believe as it's now 'out of cycle' with my other coolers which are out for cleaning and vacuum test. Given the state of my other coolers (i.e., ready for a good cleaning), this one likely is as well.

Well, it's Father's day and I'm already cleaned up to go to an antique boat show, and with other work calling me, it'll likely be Wednesday before I can get the little bugger off. C'est la vie...

I think my next little project will be to drill out a strainer top and install a fresh-water adapter so I can keep all this a bit cleaner, a bit longer, and a bit cheaper! 😁

Again, my thanks to all and Happy Father's Day!

Steve

Kallisto 5369

Yeah, taking them off kinda sucks!!

Just paying someone to clean them is multiple boat bucks

Corey
Sent from my iPhone

I recently did this as well; HIGHLY RECOMMEND!!!

Already had the adapters but decided to hardline freshwater lines with ball valves to make it all the easier to hook the boat to shore water cycle some valves and flush the main and generator. Well with the effort to make flushing so easy and buys quite the peace of mind to let everything sit with fresh water.

Just need to be mindful of letting the water flow with the engine/generator off. With the lift muffler system there exists the risk of hydrolocking. I normally ask someone to give me 15 seconds to get down to the valve and shut the engine down, I close the valve at the same time it cuts off.

were off to the San Diego wooden boat festival ourselves today, Enjoy and best of luck with the rest of the project!

-Rick

5351

Professor Covington,

I have the same gear oil cooler and tried to replace the pencil zincs in it a few years back. It was not worth the time, trouble or expense in my experience. I now rely on the freshwater flushing of the system aligned with my servicing of the aftercooler. Check out my aftercooler near disaster miss on the owners forum if you haven't already seen it. Best wishes.

~Lucky Chucky