270 Crusader Heat Exchanger question full vs half

I have a 1979 Uniflite with twin 270 crusaders. My engines have the half closed system, there is raw water in the exhaust manifolds. I saw a boat of the same vintage the other day and it looked like it had the same heat exchangers as mine yet it was a fully closed system. I am wondering if I could do the same. My heat exchangers do not have the extra pipes coming out of them. They are the 5" ones with the rubber caps held on with hose clamps. It would be nice to switch to the fully closed system without having to replace the heat exchangers. Anyone have this type of setup? Maybe with the water temperatures in the Pacific Northwest the present heat exchangers could handle the increased load of keeping the manifolds cool as well...

................................

SeeBrowser said:

I have a 1979 Uniflite with twin 270 crusaders. My engines have the half closed system, there is raw water in the exhaust manifolds. I saw a boat of the same vintage the other day and it looked like it had the same heat exchangers as mine yet it was a fully closed system. I am wondering if I could do the same. My heat exchangers do not have the extra pipes coming out of them. They are the 5" ones with the rubber caps held on with hose clamps. It would be nice to switch to the fully closed system without having to replace the heat exchangers. Anyone have this type of setup?
I do not have that exact setup, but I do have very similar units (twin SBC engines).
However, I have re-worked, repaired, replaced, altered and installed many Closed Cooling Systems over the years.
Usually when a Full System is required, the H/E (heat exchanger) is set up with the additional ports.

Maybe with the water temperatures in the Pacific Northwest the present heat exchangers could handle the increased load of keeping the manifolds cool as well...
While the seawater demand will typically undergo a very small change (going from a Half to Full Closed Cooling) if any, the size and heat exchanging ability of the shell-and-tube-bundle may change........ not to forget the additional ports within the E/G side (E/G = ethylene glycol) and a change to the T-stat housing.


In order to change this to a Full System, you will need to:
..... make sure that the H/E is capable of removing heat from not only the engine, but also from the exhaust manifolds.
..... see if the H/E can have the additional ports added to it.
..... make sure that your seawater pump is able to provide enough seawater.
..... block-off the seawater transfer ports between manifold and elbow.
..... you will need to change the T-stat housing as to accommodate coolant to/from the manifolds.
..... a means of splitting the "spent" seawater equally, and then directing it equally to the elbows. (elbows are always seawater cooled)


While I certainly like the idea of the Full System, I would ask myself if it's worth the effort and cost.

Click to expand...

.

Thanks for the reply Rick.

I have the Sherwood SP105 crankshaft raw water pumps on both engines. My exhaust manifolds are about 3 1/2 years old at this point... maybe at their end of life would be a good time to revisit this idea. Which is another question, how long can I expect the manifolds to last?

I also have a Uniflite (mine's a 1977) powered by twin Crusader 270s with the closed-cooling half system. Is your use in salt water, fresh water, or both? I am asking because when I changed out my manifolds, risers and elbows two years ago, I replaced components that were cast in the mid-1990s. The previous owner used the boat mostly in fresh water, and I use the boat for 4 months in salt and the remainder in fresh water. I'm not advocating a 20 year year replacement cycle, but I do believe that if a substantial portion of the use is fresh water, the life of the cast iron parts is longer than if used only in salt water.

Dan

Hi Dan,

My boat is used in Saltwater only... unfortunately.

There's likely plenty of capacity in the HX you have.....the big difference between the two HXs is the 'full' system has a tank for extra cooling.....

I don't see where you would have 'extra ports' - may be ports with a different orientation....you could always contact one of the aftermarket HX makers and ask them what the differences are between the two configurations......the manifolds would need the adapters and the block off plates....

As far as service life, the manifolds should last for the life of the engine as long as they are cared for.....they are about the thickest castings you will ever see.....the elbows are normal service items.....nominally 5 years for them....

Just to be clear... the manifolds with salt water in them will last the life of the engine? Thanks

SeeBrowser said:

Just to be clear... the manifolds with salt water in them will last the life of the engine? Thanks

Click to expand...

Typically salt water manifolds will need to be replaced long before the CCS engine will.