Since I am in the mood for heat exchanger repairs, I fixed my leaky dual oil cooler

This is an original 1970 part, de-soldered ends off and cleaned up.


I pressure tested the coolers and they are good.

I JB Weld epoxied it back together


I had a long standing problem with it, one of the ends leaked raw water, not a lot, hardly at all, but while running an end would get slightly wet from raw water.
Apparently lead solder over a long time in salt water, it gets eaten away. When I took it apart, one side had almost no solder in the joint.

I took it apart by having a fire in our Deck Chimenea which has a tall exhaust stack. Flames were leaping out of the stack, and I laid it across the top. Used a big plier to pick it up and it fell apart with a few taps. Did one side at a time.

Each tube cooler is silver brazed together with no lead solder.
But the ends are lead soldered onto the tubes.
They do that so it can be taken apart and fixed.

The more recent issue I had, the drain port fell apart-cracked. It was cast into the bronze.
To stop it from leaking raw water, I plugged with PL adhesive.
Then this past winter, used a drill to let it drain, and I inadvertently puncture one tube!
So couple days ago, taking it off, I saw engine oil in the raw water side. So I knew it had to come apart to repair.

I bought 40 inches of 3/16" copper nickel brake tubing from AutoZone.
Cut off a section, coated with JB weld and slid it into the broken tube. Original tubes are 1/4"
Only other option would be to solder it shut or buy a new one for $500.

Some more pics
Repaired drain hole tapped. The casting here is very thick


Repaired tube with 3/16" copper nickel tube epoxied in.
I also whacked the end over.
The entire tube length is JB welded into the original tube.
I ran a foot long 3/16" drill bit down the busted tube to make room etc...
nicely this tube pretty much fit the new tube without trouble.
The OEM maker on some other tubes spilled extra silver braze in some other tube ends.




I am happy with the repair

 

Correct. Don't use tin-lead solder on seawater anything. There are some lead-free solders that can be okay, but they aren't all the same, so it takes some looking into. It's the tin that is the problem. Some Ag-Cu-Sn solders form a decent passive layer, but I wouldn't trust it to hold up to flow in a heat exchanger.

 

I have had good result with Oatey lead free solder meant for plumbing. It is tin with a small amount of silver.
It takes more heat to melt
It is stronger than lead solder. About half the strength of bronze.

For this oil cooler, even if the JB weld leaked out water, the oil wont leak out.
I have a good feeling it will hold up better than a lead solder.

 

This piece screws into the oil cooler, it has been 55 years in salt water, check out how well it has survived. All raw water flows through the heat exchanger to the oil cooler, other side of this here, this part takes the exit water from the oil cooler.

This parts splits the exit water stream, part goes to the riser extensions, and part goes to the large bronze exhaust mixer with large rubber exhaust hoses.
These are v8 engines. So the exit water flow going to the riser (the elbow) also has a Y splitter connected to that elbow for each riser of the V8 engine.

All Nibco parts. Nibco made good parts.

Another good reason for repairing my existing dual oil cooler besides the large cost, I don't want to re-plumb all this stuff.

 

Here is a pic from a video I made after I rebuilt this engine years ago.
The red hoses carry raw water pump to riser extensions.
The exhaust manifolds and risers are FWC, connected together.
It was not like that OEM, I modified the risers. I brazed 3" bronze pipes 6" long to the riser exhaust exit, plugged the single internal raw water discharge hole, drilled an angled hole in the bronze 3" pipe and silver brazed 316 SS pipes to carry raw water to the new riser exhaust exit. I did this soon after I got the boat in 1998 and bought new risers, so these risers have lasted 26 years without a problem.
Risers are number Bar 20.0000

If I did this today, I would put a higher angle on those SS pipes to bring them down lower. The riser original raw water exit hole shoots straight back into the exhaust stream, parallel with the flow.

Gives you the scheme of how the oil cooler fits. I have since then, gotten rid of the awful vane fuel pump and use a pulse pump now.

That vane pump churns the fuel heating it up and that style pump wears out quick.
When they wear out, they no longer can suck fuel.
I found them highly unreliable. They also corrode internally with E10 gas. and you must use a pressure regulator as the one they have internally fails and the PSI spikes up, I went through 5 pumps before switching to pulse jet fuel pumps, and been good, no external regulator needed. And they suck fuel well. That vane style pump came out in the 1920's!

I could go back to OEM rubber diaphragm fuel pumps, but I like being able to prime my carbs versus cranking of engines.

 

Does anyone know why these oil coolers do not have zincs?
I went looking and some do and some don't.
Then someone on another boat forum said the underwater zincs help protect these, as they are all connected electrically.

 

But they aren't in the same environment temperature-wise. So the galvanic potential will be different because it depends on temperature. In Florida, my pencil zincs lasted a year even if I never ran the motor.

 

It is interesting they have survived such a long time.
I gave owned boat since 1998, and these coolers, other engine has one too, looked old back then.
The other engines oil cooler is a replacement, it looks identical except there is no mounting soldered on the bottom, it uses a strap.

These coolers bolt to 2 small rectangular flat plates which plates then bolts to the velvet drive. Allows for mounting an different ways.