Replace just the elbows??

Todd320

Todd320

Well-Known Member
Jul 21, 2016
1,508
St. Petersburg, FL
Boat Info
2007 Sea Ray 320DA
Engines
Twin V-drive 5.7L 350 Horizon
What is stated below is my understanding in looking at the engine diagrams! Please correct me if I am wrong!!

I have closed cooling on 2007 Mercruiser 350 MAG Horizon MEI (serial 0W399144)
Since this is closed cooling, the only part of the elbow-riser-manifold that touches salt water is the elbow (the salt water is discharged there). There is a blocking plate, and it prevents the salt water from touching the coolant.
Seems like to me, I should replace the blocking plate, and/or the elbow, more frequently and if I do that, I see no reason to replace a manifold/riser if it never touches saltwater. Is that correct, what am I missing??
Any mechanically inclined/mechanics who can help me potentially avoid a major expense or steer me in the right direction? Granted, the manifold and risers only add
Here are the Mercruiser parts for the elbow and blocking plate.
288B05AA-A0D9-47E4-A856-8061D0677493.jpeg
4A59497A-2583-4F72-B3E0-1ECCD6998248.jpeg
 
Makes sense if there’s no water going through the manifolds. My 8.1s horizons are a 50/50 system, so the block has coolant, but manifolds and risers are raw water cooled, so I replace both every time.
 
Hard to tell for certain. The riser kits that were installed by PO’s marina was 864929A4, 3” risers, which per Mercruiserparts.com, includes 3 gaskets, block-off, full flow, and restrictor. They are all labeled as 13, but there are only 2 in the graphic, one above and one below the riser. I’m guessing the riser kits include 2 risers, since they only installed 2, but they installed 4 elbows, and 4 manifolds.
 
Here is my closed cooling diagram. I marked it up in red where I think the seawater flows, and green where the coolant flows. But, I’m just guessing.
83332762-FAA3-4A1C-89D4-8345FB342EA2.jpeg
 
Did this last year, if closed cooling you just have to replace the elbows. 3” Spacers are fresh water as well so you don’t need to replace them but you should change all the of the gaskets. If you go to NuWave marine they will confirm the necessary open/block off gaskets.
 
Yes i would say u can only repalce your Rises and Spacers.... But then ask your self things still go bad.... When was the last time Manifolds were changed? I would say you have a good 10+ years on manfold, because Antifreeze is a anti corrosive and If you in that range ur fine... But if your over it, i would hate it for you to cost you a motor for a few hundred more....
 
Siboatguy said:
Yes i would say u can only repalce your Rises and Spacers.... But then ask your self things still go bad.... When was the last time Manifolds were changed? I would say you have a good 10+ years on manfold, because Antifreeze is a anti corrosive and If you in that range ur fine... But if your over it, i would hate it for you to cost you a motor for a few hundred more....
Click to expand...
Manifolds/risers/elbows were replaced at the end of 2015, and I think that was the first time they were ever replaced. So, that seems to correspond with your 10 year plan.
 
Irie308 said:
Did this last year, if closed cooling you just have to replace the elbows. 3” Spacers are fresh water as well so you don’t need to replace them but you should change all the of the gaskets. If you go to NuWave marine they will confirm the necessary open/block off gaskets.
Click to expand...
Sounds great! Regarding the gaskets, did you do the gaskets below the spacer (between manifold and spacer), or just the ones between the salt water and coolant (between the elbow and spacer)?
 
I called mecruiser twice and got a different
Answer both times. In my area of brackish water. I check evey 5 years.
When I did mine last year they were original and looked very good. Could have gotten a few more years.
Full salt water is a different story.
 
Changing manifolds while you are changing elbows is ALOT cheaper than changing an engine ;) JMO
 
Todd320 said:
Sounds great! Regarding the gaskets, did you do the gaskets below the spacer (between manifold and spacer), or just the ones between the salt water and coolant (between the elbow and spacer)?
Click to expand...
Yes, they were relatively cheap so i did them all at once. Also when removing the elbows you may unseat the spacers so to ensure a nice tight fit i cleaned up all the joints and replaced the spacers. Make note of what gasket goes where. I believe one of them is called a turbulator that has a flange that has to face upwards which prevents fluid from dripping down the sides of the elbows into the manifold. Its a bit confusing on paper but when you start removing them it will all make sense. The diagram is accurate above however they don't take into consideration the spacers. Make sure you give them your serial number of your engine when purchasing as i think there are two different types of elbows (based on angle). There is no need to touch the manifolds if they are closed cooling. Seawater never touches the manifold jackets unless you have a leak from the elbows in which it will be leaking into the exhaust ports of the manifold and it will be obvious once you remove the elbow.
 
superwa said:
Makes sense if there’s no water going through the manifolds. My 8.1s horizons are a 50/50 system, so the block has coolant, but manifolds and risers are raw water cooled, so I replace both every time.
Click to expand...
You replace both! The elbows are stainless.
 
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