exhaust question - closed cooling

[whiskeyRichard]

picture attached

On my boat, the exhaust manifolds get engine coolant circulated through them to cool them down. The exhaust riser gets lake water injected into them which then flows out the exhaust back into the lake.

Since the water jackets on the risers and manifolds come together, the previous owner fabricated a paper gasket that blocked the passages on the manifolds and risers from connecting effectively acting as a barrier with lake water on one side (in the riser) and coolant on the other side (in the manifold).

I took the risers off to inspect them. They were fine. I did not like to idea of the paper gasket in there as the only barrier to the lake water in the riser and the coolant in the manifolds, so I CNC cut some block off plates and used gaskets on either side of them instead.

I was thinking tonight, why not just pump the lake water into the manifold, not have the block off plates at the risers and letting the water flow up through the riser and back out into the lake. It seems like it would take a load off of my cooling system.

Other than a little more work to winterize because I would need to drain the manifolds as well as the risers, is there any drawback?

Thanks

 

[achris]

One of the purposes for closed cooling the manifolds is to eliminate the water path between manifold and elbow. That's the one that causes a lot of grief when it fails (not 'if')... By putting the block-off gasket there, that path (and hence the corrosion associated with the flow) is removed. It also means the manifolds are pretty much 'for life'... The HE has capacity to spare, even cooling the manifolds.

Chris......

 

[Scott Danforth]

going from a full system to a half system means that your manifolds will now be a service item along with your elbows vs just the elbows being a service item as Chris mentioned.

a properly sized heat exchanger will cool both the manifolds and the motor without a problem. I would personally keep a full system vs going to a half system

 

[alldodge]

Agree would keep the system as is.

If your in fresh water you could do it and your manifolds would last the life of the motor without issue, but not if your in salt

http://www.westcoastoffshore.ca/Kodiak-Exhaust-Manifold-38-Riser-Hex-Nuts-HN06F-P11349.aspx

 

[whiskeyRichard]

got it, thanks for the responses. She's stays a full system.

Lets see what hair brain idea I can come up with next.............

 

[tpenfield]

You can, and should, buy the correct 'block-off' gaskets. There are also aftermarket Stainless block-off plates that can be used in combination with the gaskets.

 

[Lou C]

As long as your HE can take the heat load, I'd leave it as it, and only have to eventually replace the elbows.

 

[HT32BSX115]

Other than a little more work to winterize because I would need to drain the manifolds as well as the risers, is there any drawback?

Thanks

Howdy,

Your best bet is to stick with the block off gaskets and adding a plate or use the stainless plate-type gaskets :thumb:

There's only one way to improve on what you have and eliminate the "gasket" If you have a small block GM engine (or it's an 496 bigblock) , you could change to "Dryjoint" manifolds and risers.

Gaskets are not needed with those type manifolds and risers because the cooling jackets for them are isolated from each other.

I with someone would produce dryjoint manifolds for the 454/502 engines. I would switch in a heartbeat!!

Happy Holidays everybody!

Rick

 

[scoflaw]

Several aftermarket companies make them for the 7.4 and the 8.2. Manifolds are aluminum thou

 

[HT32BSX115]

Several aftermarket companies make them for the 7.4 and the 8.2. Manifolds are aluminum thou

Hey, thanks for that!

I installed closed cooling on my 7.4 Bravo when I installed the engine. I know about the stainless steel welded types, but I would rather have cast and would need 3" riser extensions too.....

Can you post the make/model of those manifolds & risers or send me a PM?

I had an OEM block-off gasket leak on one side a few years ago. It didn't seem to hurt anything but I would really like to have dry-joint type manifolds and risers to prevent that permanently!



Thanks!

Rick

 

[scoflaw]

Gil Exhaust
EMI Eddy marine
Stainless Marine
Dana Marine

 

[Bt Doctur]

The Wellcraft 28 coastal with Bluewater inboards uses a SS block off plate and 2 standard gasket above and below.
Never a problem. Have had more problems with the graphite blocking gasket on some motors

 

[Scott Danforth]

Rick, once you pick up an aluminum manifold such as those listed by scoflaw....you wont ever want to lift an iron manifold again. I think the difference in weight is 45# per manifold

 

[alldodge]

Eddie Marine type

 

[whiskeyRichard]

You can, and should, buy the correct 'block-off' gaskets. There are also aftermarket Stainless block-off plates that can be used in combination with the gaskets.

I called the manufacturer of kodiak manifolds and for the manifolds/risers ones I have, there is no block off gasket. I just used the regular gaskets one on either side of the SS block off plates that I cut on my CNC table. I cut the plates from 3/16. They are slick.

 

[HT32BSX115]

Gil Exhaust
EMI Eddy marine
Stainless Marine
Dana Marine

Found them, thanks.....

Definitely NOT "cheep" though.........

 

[achris]

Found them, thanks.....

Definitely NOT "cheep" though.........

Good no cheap, cheap no good.