1969 Chris Craft Roamer Refit: Reassembling the Aftercoolers

Winter 2016 is over in the Mid-Atlantic region (got my first mosquito bites of the season..three in a row on my buttocks!), butt…I haven’t gotten Zika or Dengue (yet), so I’m still thinking I can splash later this year. To that end, I’ve got a relatively short honey-do list: 1) seal up the boat, and 2) get the engines running. Within the short list, there are lots of individual things that make the more refined list much, much longer. I’ve got a challenging number of things that have to be done…challenging, but not impossible.

Aftercooler housings got coated with other Cummins parts

Recently rolled-on Devoe 235 Epoxy coating comes off easily with a razor

Degunked aftercooler core slides into the well-greased housing

Generic o-rings: $4.88, a small fraction of the Cummins $77 list price

I was surprised by how much Cummins prizes their o-rings: $35 for a set of two rubber o-rings, and two kits are required for twin-engine applications. The OE o-rings are 125mm x 4mm, so I spent two minutes on the ‘net locating a company selling bags of five o-rings for a whopping $4.88, including shipping…less than a buck apiece. Fortunately, they’re not classified by the government as hazardous material, so the price was very reasonable.

Well-lubricated copper end caps are ready for installation onto the aluminum aftercooler

Word has it there can never be too much grease when reassembling these aftercoolers, and I believe it. The aftercooler housing is aluminum, and everything else is copper, bronze, or galvanized steel, all in a place where condensation is guaranteed to happen. Grease and regular maintenance are the only way to avoid expensive repairs in the future…and I’m OK with that. I’m really looking forward to the time when maintenance is all I’ve got left to do on this boat.

More grease…just because.

Tefgel to keep the new shoulder bolts from getting too friendly with the aluminum

Installed and ready for zincs

One more check on the honey-do list

In other news, my new AHP TIG welder has arrived and I’m slowly accruing seat time figuring out how it all works. TIG is a very different process than the MIG welding I’m more familiar with, but this new AHP machine makes it a lot easier than the last time I tried gluing aluminum together using the TIG process…when I ended up melting the whole thing into a blob on the bench! High frequency start and run (for aluminum) and AC balance are truly things of beauty, and the weight difference between my old transformer-based Millermatic 35 and this new inverter-based AHP makes the prospect of doing onboard welding less of a dread-inducing prospect. But while I’m getting up to speed on the new TIG in my home garage, I’m also working on more honey-do items on the boat.

Next up in our 1969 Chris Craft Roamer 46 Refit: The V-berth Head.

1969 Chris Craft Roamer 46 Refit: Servicing the Aftercoolers

The Cummins 6CTA engines in my Roamer are aftercooled turbo diesels. The aftercooler housing is cast aluminum, but the core is made of bronze. Since raw water runs through the core, these aftercoolers are notorious for the sort of corrosion problems you’d expect from dissimilar metals in saltwater. Making matters worse, Cummins apparently assembles the aftercoolers dry, with no grease, Tefgel, or anything else to lubricate the joint, isolate the metals, and make disassembly easy. These engines only have 400 hours on them, but they came from New York and ran in saltwater. There’s just a bit of the green verdigris around the lower aftercooler end cap, which is telling me it’s time for service. The diesel gurus at boatdiesel say the aftercoolers should be serviced every two years, and I’ll be following Tony Athens’ method.

Aluminum + bronze + saltwater = a few minor problems

After I popped the top off the aftercooler, I found a bit of aluminum and copper oxide outside the o-ring seal. This tells me there was a slight leak at the o-ring. I’m glad I decided to tear into this.

Green powder = evidence of an o-ring leak on the bottom, too

Bad hardware choice…add steel to the mix of metals

The hex bolts holding the ends on the aftercooler are standard sized. Unfortunately, that brings the edges of the hex heads so close to the bronze castings that a socket won’t fit. This isn’t a good scenario for an aftercooler that was leaking saltwater.

Bolts came out without snapping

I need to order new galvanized shoulder bolts for when I reassemble this. And they’ll get slathered with Tefgel when this goes back together.

Salt plugs one tube

Salt cleaned up pretty good

Light at the end of the tunnel?

The core tubes are clear now, so water flow won’t be restricted anymore.

Second aftercooler has similar issues with the o-ring on the top end

Cleans up pretty good though.

The water side of the aftercooler cleaned up pretty well, but the air side is still a question. Because the bronze cores were installed dry into the aluminum housings, I couldn’t convince them to come out. So I brought both aftercoolers down to the house, stood them up on end, and poured some automatic transmission fluid into the air side. Two days later, ATF started dripping out of one and a week later it started dripping out of the other. I flipped the housings over and repeated the process. Finally, after two weeks, some heat from a MAPP torch, and occasional encouragement from a 3# sledge hammer tapping on a block of wood laying across the top of the core, first one then the other core came out.

The core is not too bad

Needs a good soaking and clean up

Fortunately, the fins all look good and the corrosion on the ends was minor.

Sloppy solder work in one spot, but that shouldn’t affect the aftercooler

I’m soaking both cores in degreaser now and will clean them up over the weekend, then I’ll reassemble next week. In the meantime, the window shop finally sent replacement trim rings for my helm station windshield. Adding to the potential drama, a blizzard is forecast for the area tomorrow and Saturday, with 50mph gusts and no less than 12″ of snow predicted. We’ll see how Tent Model XXX holds up.

Next up in our 1969 Chris Craft Roamer 46 Refit: Mid-Atlantic Blizzard 2016