Heat Exchangers

[Bowdrie]

Several months ago, I reached out to Celestialsailor in regard to the heat exchanger on the engine in his new boat.
I told him that I had developed a "work around" for the molded rubber end caps on his heat exchanger as I had the same problem.
Many engines from "back in the day" used heat exchangers that were made by "San Juan Engineering", and they used a proprietary molded cap which had a raised groove section which fitted over a central "fin", as it were, to divide the flow in a 2-pass cooler.
That company was bought out ~5 years ago by "Orca Marine Cooling Systems", and those rubber caps are long gone.
Some have popped-up from time-to-time, but the ones for the 3" tube bundle are almost non-existent.
Needing one for my own engine I came-up with a work-around which works quite satisfactory and is cheap to do.
It consists of a section of wet exhaust hose, a fiber glassed plywood disc, and a short section of ~3/8ths OD hose, (the kind that's commonly used for vacuum service in automobiles).
I think the pics are fairly self-explanatory, the short little hose is slit and snapped over the fin in the exchanger and forms the seal against the wooden disc.
Yes, there may be a little leakage across the sections, but not any more than the original caps, the key is to hold the disc under some pressure whilst you tighten the clamps.
Ok, so here are the pics, the first shows the "stock" cap with the exchanger, the second shows the little hose over the fin with the large hose installed.
Then the wood disc is just pressed down against the little hose and tighten the clamp that holds it into the big hose.

[Bowdrie]

Here is a pic of the exchanger ready to go back on the engine.
I've done both ends with my set-up, and no problems.
Easy to do with minimal effort and parts.
Instead of the little hose one might use a piece of Neoprene, or even some adhesive weather stripping, anything really to affect a reasonable seal between the end cap and the center fin.
Note: the center hose clamp on the left end is just "storing a spare clamp".
Also, what they call a "3" tube" is NOT accurate. the hose size necessary to fit is 3-1/8", and fortunately that size is readily available as a marine wet exhaust hose.

[Celestialsailor]

Bowdrie...I am not seeing pictures...

[Bowdrie]

Originally Posted by Celestialsailor

Bowdrie...I am not seeing pictures...

You mean the pics only show on my computer.

[Celestialsailor]

I do not see any attachments

[Bowdrie]

Originally Posted by Celestialsailor

I do not see any attachments

I have no idea, I've posted pics before several times, and all went well.

[Bowdrie]

Pic 1, pulled it off of Bing

[Bowdrie]

Pic 1,
https://www.cruisersforum.com/forums...1&d=1664295752

Pic 2,
https://www.cruisersforum.com/forums...1&d=1664295752

Pic 3,
https://www.cruisersforum.com/forums...1&d=1664295752

[Bowdrie]

Sorry for the issues I had with the pics.
The originals were too big to post, took me awhile to figure out what to do.

[Celestialsailor]

Looks like a good solution. Is there a test you can do to ensure the coolant side is completely sealed off from the raw water side?

[Bowdrie]

Originally Posted by Celestialsailor

Looks like a good solution. Is there a test you can do to ensure the coolant side is completely sealed off from the raw water side?

No, both sides of that center fin are raw water.
The raw water enters the bottom on one side of the fin, it then travels thru the tubes to the other end, and then travels back thru the upper tubes which terminate on the upper side of the fin, thence to the exhaust elbow.
Am I describing the flow in an understandable manner?
The raw water makes 2 passes thru insides of the tubes in the bundle.
The coolant side is within the bundle, but on the outside of the tubes.
The separating fin has nothing to do with the coolant, it only diverts the raw water flow.