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LM318 osco manifold full cool set up question

K

KMD

Member
LM318 with log style manifolds. Current manifold set up is OSC826 manifolds, 689 riser, 794 elbow. Most of the set ups I have seen block flow between manifold and riser. Then the riser/elbow are salt water cooled. Is it possible to block flow between the riser/elbow making the riser also FWC’d? I know anything salt water cooled will be trashed in 5/10 years just trying to get as little salt water cooled as possible. Is it because you would not get a good flow pattern through the riser since its sort of dead space?
Second question In the past I have always used a stainless steel block off plate between manifold/ riser when making manifolds full cooling. I called up osco motors when I could not fine SS block off plates and they said thay just use the gasket (480-FW) and that is it. I just cant see how over time the gasket wont leak through. If I cant find one I was going to buy some 18 GA SS and make my own.
 
You cannot FWC the riser. One of the risers jobs is to mix sea water with the exhaust to cool the exhaust. The block off gaskets will last about 5 years, the same as your riser. Your RWC riser has a 5 year life.
 
Ditto Chris.
The elbows provide the sea water mixing chambers, and must remain fed with spent sea water.
This is "total loss", as apposed to "captive".

And I'd not use gaskets only.
The SS plates w/ gaskets will ensure complete close off between the two sides of the system.


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RicardoMarine said:
Ditto Chris.
The elbows provide the sea water mixing chambers, and must remain fed with spent sea water.
This is "total loss", as apposed to "captive".

And I'd not use gaskets only.
The SS plates w/ gaskets will ensure complete close off between the two sides of the system.


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Click to expand...
Most block off gaskets offered by OSCO have a thin metal membrane. They will last about 5 years.
 
Thanks for the reponses. I bought these motors and they were fresh rebuilt and never installed in boat (new manifolds). I pulled off a riser/elbow to see where the block off plate was and see gasket configuration. The block off gasket was a green gasket but I didnt see any metal in it.

Do you know if any body makes after market SS block off plates for these manifolds? I use to be a sheet metal fabricator in a previous life and I can get some 20/18/ or 16 ga stainless and make them but that would be a PITA.

I live in Middle chesapeake bay (solomons island), are water is brackish we typically get 10 years out of manifolds but always measure temps just to ensure proper cooling throughout the season.

Thanks again
 
I boat north of you!

Let's define a few things here: What I call the "riser" is the part that liftsd the exhaust and water higher (hence its name). What I call the "elbow" is where ther water and exhaust finally meet.

I don't see any reason why you couldn't glycol cool the riser, but not the elbow. The bolt pattern at the elbow/ riser joint is similar to the other side of the riser, and there's good sized water fittings on it.

I'd say go for it!

Jeff
 
fastjeff said:
1... Let's define a few things here: What I call the "riser" is the part that lifts the exhaust and water higher (hence its name).
What I call the "elbow" is where ther water and exhaust finally meet.

2... I don't see any reason why you couldn't glycol cool the riser, but not the elbow. The bolt pattern at the elbow/ riser joint is similar to the other side of the riser, and there's good sized water fittings on it.
Click to expand...
Jeff,

1... Excellent point. I've found myself guilty of calling an "elbow" a "riser".
Technically, these are elbows, and the "riser" is actually a ported spacer between the manifold and elbow.


2... True.
Often risers/spacers are looped in with the Closed Cooling system, and are blocked between themselves and the elbow. The elbows are then ported for the spent sea water.

For elbows that are NOT ported, then the riser/spacer becomes blocked off underneath it, and remains in the spent sea water path.



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