CAT Aftercooolers — and whats Real

In your boots, I'd take the opportunity to install also a fresh water flush connection.
It was discussed in this thread, from post #40 onward.
God only knows by how much it will lengthen the life of your CACs (and also of other bits), but pretty sure it won't hurt.
All the lake boats out there are a living proof that boat engines are happier to live in fresh water...

U R welcome, I hope it will prove effective for you.
It certainly did for me so far, though with different engines.
But the principle is valid in general, and possibly even more with Cats, considering their recent coolers history.

My theory is that CAT loves to mount the aftercoolers on top of the motor. My theory is the sea water drains out of them, air is in there along with concentrated salt and allows a lot more corrosion to happen.

I'm not saying that your theory is wrong, but it's not like Cat is alone in that design.
In my 17 years old MANs, whose CACs are also on top of the engine, they were never replaced.
And based on how they looked when stripped and cleaned a couple of years ago, I would expect/hope them to do their job for many more years - though I'm saying this with my fingers firmly crossed, of course.

Btw, my last boat before the current one was Cat 3116 powered, and even if those engines certainly aren't among their best ever, they are still working just fine now that they are 26 years old, and with their original coolers.

I mean, it's not like we're talking of rocket science here.
In fact, I'm wondering how long it will take before someone will put together a class action against Cat on this issue - unless someone already did and I missed it, maybe...?

My point exactly!

Man's heat exchangers are isolated with rubber o-rings and have no zincs. Something is obviously wrong in the CAT camp regarding the aftercoolers, because you're right, I have MAN's, cummins, etc etc. all running after coolers approaching 2 decades old. SO, is it the zincs themselves interacting with them, the design themselves, the type of metal, IDK.

It should be easy enough to find a new vendor for aftercoolers.

Your engines may have antifreeze cooled aftercoolers which have a longer life than the traditional raw water cooled systems. The aftercooler cores are aluminium in the c12 cats, they are not one piece and bronze like the MANS. If yous are like my c12s the aluminium core gets thin overtime and then eventually leak water into the engine intake and BOOM.

You can roll the dice and wait and rationalize your decision but the question becomes do you want to spend $$ now and follow the CAT recommendation or put your 100k engine at risk of serious damage.

Maintenence on the high performance diesels can be expensive but it's part of the equation.....
I saw your post on BD site, dave is the CAT guy over there. Do a search you will find info on your exact question
Good luck
Let's s know what you decide to do

Going a bit O/T now, and I apologize with the OP for this, but you are raising an interesting point.
There is in fact quite a bit of confusion on MAN's anodic protection (or lack of).

The reason why there are no zincs anywhere on the engines is that they are bonded with a large external transom anodes, whose main advantage, arguably, is that it's harder to miss when it must be replaced, compared to several pencil anodes somewhat hidden around the engines.
But this is all well and good, that's the way MANs were designed.

Where in my experience MAN recommendations clashes with the reality (and I guess it's the reason why you are suggesting that their coolers are isolated) is when they suggest that engines should be isolated from the rest of the onboard DC circuit.
I've seen plenty of MAN powered boats, built from several different builders, and in all of them, bar none, the engines were earthed with anything else onboard.
In other words, I've always seen engines and all their bits (HEs and CACs included) bonded with seacocks, domestic DC bank negative, and anything else bonded onboard.

If by chance you would come across a boat where this doesn't happen and engines are fully isolated, I'd be curious to hear who the builder is, because obviously that depends on the installation, rather than on the engines themselves.

All that said, back to the point, yes, no doubt there's something very wrong with these Cat components.
Both the explanations from CR (poor soldering) and BC (aluminum cores) could be valid, but the latter sort of contraddicts what CR said about never having found any metal issues...

Had a Man mechanic tell me Man engines have an isolated ground and bonded to the transom zinc, no aluminum coolers. Seems Cat could easily duplicate that, they have had aftercoolers issues for a longtime. Odd that Cat uses a titanium plate H/E and questionable aluminum A/C on many models?