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Even though my Cummins engines started up and ran fine on the pallets when I bought them, I decided to follow the advice of some gurus and service the aftercoolers. Good thing I did, too--the magical combination of a cast aluminum housing, bronze core, steel bolts, and saltwater had begun to cause minor problems that would have turned into expensive problems if I hadn't taken the aftercoolers apart.

Oh, and there's a blizzard forecast for tomorrow. This will be the big test of Tent Model XXX.

1969 Chris Craft Roamer 46 Refit: Servicing the Aftercoolers

Cheers,
Q

Roamer46, how about an anadizer metal???

ER, a "zinc" would only slow down corrosion.

Guys, for the most part, you absolutely CANNOT
use dis-similar metals around salt water,

In my (10+ years of being around aircraft) opinion,
the whole system should be made out of Stainless Steel,
and the right mix to protect from DM corrosion.

Q, what is this 12 inches of "snow?" From what Google
tells me, that looks like the stuff that builds up in my
freezer! Before I lived here, I lived in Hawaii.
We called "snow cones" shave ice, because NO ONE knew
what "snow" was.(Hope you weather the storm OK!)

steve

Steve, may your ice maker go on the fritz someday soon...ideally, while I'm shoveling snow.

There actually are zincs in each aftercooler. They help a bit, but Cummins' dry assembly is just not a good way to go. Also, the aftercoolers will tend to collect condensate on the air side almost by design. Pulling the zincs after every trip would solve that problem, but who does that?

ERLover, if you figure out a process for having different metals--especially aluminum and copper--in water without having chemical reaction happen, you will be a very, very rich person. Each molecule of aluminum oxide occupies a space something like 21x bigger than the space occupied by the aluminum and oxygen before they react. When you're talking about the very small gaps between these parts, it fills up very quickly with very little aluminum lost to corrosion. Fortunately, heavy applications of grease and good o-rings seem to resolve the problem so long as you keep up on the maintenance. They say it's not too difficult of a job once you do it the first time. Luckily, I got to these before it was too late.

@Roomer,>ERLover, if you figure out a process for having different metals--especially aluminum and copper--in water without having chemical reaction happen, you will be a very, very rich person. Each molecule of aluminum oxide occupies a space something like 21x bigger than the space occupied by the aluminum and oxygen before they react. When you're talking about the very small gaps between these parts, it fills up very quickly with very little aluminum lost to corrosion. Fortunately, heavy applications of grease and good o-rings seem to resolve the problem so long as you keep up on the maintenance. They say it's not too difficult of a job once you do it the first time. Luckily, I got to these before it was too late.
I just gave a suggestion, not a chemist, and my boats were slipped and used in fresh water, I know salt water is a whole other thing, but no experience in it. Forgive me

Roamer, I'm just saying what I learned in 10+ years working on
airplanes. Aircraft were not, for the most part, sitting in salt water.
(The world's best transmitter of corrosive electrical communication.)

But, sea planes were, sitting in salt water, as well as being asked to
fly. PLEASE, for the sale of YOUR boat, make DEAD sure you don't
have ANY dis-similar corrosion issues. One more concern, salt water
conducts electricity very well. That piece next to that other piece,
an issue. That piece, 4 feet away from the other piece, if you have
dis similar problems, it will find you, if BOTH of them touch the same
water.

Bro, what I'm trying to impart, is it is better to be sure, than not.
I'd HATE to hear about this boat going down, because of some
corrosion you could have prevented.

"Steve, may your ice maker go on the fritz someday soon...ideally, while I'm shoveling snow. "

What is that, that you're shoveling? Cleaning out the icebox?

Roamer, Sincerely, I wish you ALL the best!

steve

My ER Buddy late nighter, later then JPG, good evening!!!!! Just got a SS Pro Planer on its stand, $525, Oh Ya an other one in the stable, just need that 4th ER with a SC!!!!!!!

Good score, ERLover!

Steve, if you go waaaaay back near the beginning of my refit blog, there's an article on the rudders you might find interesting. Imagine plain steel rudder shafts running through Schedule 80 aluminum pipe rudder logs that were threaded at the top. Then, to keep the water out, they used shaft packing held in place with bronze gland nuts that were threaded directly onto the aluminum. I couldn't remove the rudders with heat, penetrating oil, a 10# mallet, or a 12-ton jack! Check it out: https://1969chriscraftroamer46.wordpres ... t-rudders/

For the aftercooler, though, it all comes down to regular maintenance with lots of grease and good o-rings.

Sometimes I just shake my head at the way some otherwise good manufacturers mix metals in heat exchangers for salt water use. I had several Mitsubishi diesels at one time that employed exchangers that had bronze cores in aluminium cast tanks. The metals were isolated with O rings. There were zincs and they worked if you changed them often enough but in the end I threw them all out and installed copper/bronze keel coolers.
In general I like to keep my submerged metals to stainless (316) and good high copper bronze.
They are relatively close on the galvanic scale and not hard to control with zincs.

Have you considered one of the induced current systems that sense the galvanic current and neutralize it with an equal but opposite current?

We have been changing out all the through hulls as they need replacing with the titanium versions and on the next haul out this spring I will replace the last of the bronze fittings. We are very happy with the results. There is no corrosion whatsoever. Although they are pricey the overall cost is negligible because it appears they may never need replacing.
Paul