496 8.1 Elbows leaking. Saved motor!! READ

mnm99

mnm99

Well-Known Member
Oct 2, 2015
2,447
Long Island
Boat Info
2004 340 SeaRay Sundancer
Engines
Twin 8.1 Merc
Just passing it along guys. This may save a motor. These elbows are stainless steel, but don't last forever. These have 13 years fresh water and 5 years salt. I'm a little fanatical about my boat and making sure everything it tip top. This year I replace my raw water pumps and to make it easy I took off the 2 exhaust tubes off the elbows. At that time I noticed a little condensation inside the elbow. Started to make me look into it. So this weekend I started up the engines and ran them for like 10 min each. Got them nice and warm and pulled the exhaust tube off. There was all carbon in them except one dime size spot that looked like condensation.. HUH. I wiped it off and noticed a little paint came off.
Fast forward.. I took that one off, put it on my bench. Made a gasket with a plate and bolted it on my new manifold I am installing next year. This will be my 6th season with them flushed every time with fresh water. I capped off the elbow, filled the water passage with water and pressurized the exhaust. This is what I found at 5psi. WAIT FOR IT... As you can see there is a leak!!! Just ordered 4 new elbows from PartsVu. Get them now, I was told Merc priced are going up Mid April 10%.

https://youtube.com/shorts/lc4uRPGhr1g?feature=share

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Yes on my friends boat he had to rebuild the heads, The guy he brought them to said you need to change the elbows and his reply was they are SS and the guy said I have been doing this for 30 years you need to change the elbows.
On his all we did was cap off all the hose connections, filled with water and put it on a paper towel, It didn't take to long before the paper towel was wet.
So after we looked into this we found the weld in the SS elbow had a small crack and it an was leaking water at the crack.
So yes check all the elbows even though they are SS.
 
Same issue for us on our 340.

Was doing some spring maintenance and pulled the elbows to find the horror of severe manifold corrosion and clearly some water was getting to the valves on one side of each engine. Lucky that most of the water drains through the dripless or it may have cost us the engines.

I rigged up some plugs so I could pressurize the manifolds. Oddly, no leaks. Must be the elbows ( one on each engine ). Some more rigging plugs and was able to show where the leak was located.

6K later………. 4 new manifolds and elbows.

Here is a photo:
251ABA88-D56F-4A17-A122-13B576D8832C.jpeg
 
NEpilot said:
Same issue for us on our 340.

Was doing some spring maintenance and pulled the elbows to find the horror of severe manifold corrosion and clearly some water was getting to the valves on one side of each engine. Lucky that most of the water drains through the dripless or it may have cost us the engines.

I rigged up some plugs so I could pressurize the manifolds. Oddly, no leaks. Must be the elbows ( one on each engine ). Some more rigging plugs and was able to show where the leak was located.

6K later………. 4 new manifolds and elbows.

Here is a photo:
View attachment 124918
Click to expand...
Glad you caught it. I'm so pissed.. I ordered 4 new ones while I was on vacation. I got home at 12AM Friday night and my hauler was coming at 3pm Sat. I was going to install all 4 before he came. I opened the box and I ordered the wrong ones. I need the 2 inch rise and ordered the standard. I ended up ordering the correct ones and now there $300 more. I ended up putting the old one back on and was able to drive it to the slip. When they come in I'll replace all 4 in the the water.
 
Funny story, just opened the boxes for the new elbows and they look short to me. I have them the serial numbers so would have thought the correct ones were ordered.

It appears I also need to return the standard elbows and order the ones with 2” rise.

Can anyone confirm we all use the 2” extension elbows? The exhaust goes into lift mufflers so part of me is wondering why we need the taller ones I have also found references that the 2” extensions are for boats with outdrives vs v-drives.

Not being the 1st owner I’m not 100% sure which ones are supposed to be on the boat.
 
I’m curious about the 2” rise. When I bought my boat, port is shorter than starboard and it drives my ocd crazy. They are on my list to replace both and make them match. Both sides seem to work fine.
 
NEpilot said:
Funny story, just opened the boxes for the new elbows and they look short to me. I have them the serial numbers so would have thought the correct ones were ordered.

It appears I also need to return the standard elbows and order the ones with 2” rise.

Can anyone confirm we all use the 2” extension elbows? The exhaust goes into lift mufflers so part of me is wondering why we need the taller ones I have also found references that the 2” extensions are for boats with outdrives vs v-drives.

Not being the 1st owner I’m not 100% sure which ones are supposed to be on the boat.
Click to expand...

I had the old one on the bench with the new. The new was 2" shorter. Yes we need the 2" rise. Kinda stinks. I wonder if they will help with return shipping. I'll find out tomorrow.
 
When I bought my boat in Oct 2019 the seller told me he changed the manifolds the year before but said the risers don’t need to be changed because they are stainless. My mechanic told me the same as others here have said that they tend to leak from the welds and they need to be changed which we did that winter. Better safe than sorry.
 
I’m just curious since I had a 320DA where the engine room was so tight that you had to step on the risers to get to various items in the engine room. If that is the case in the 340DA that can’t be good for the health of those welds.
It seems that most documented actual cases of this are in 340DA’s.
 
Just a FYI...NOBODY has them:mad:. I just returned the wrong ones. Went to order the new ones since they did say in stock. Turns out there not. Nobody has them and merc says mid to end of May! i'm a little pissed to say the least. Just put the boat in the water on Saturday...
 
Any possibility of having the old ones re-welded and pressure checked?
 
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joeyleggz said:
Any possibility of having the old ones re-welded and pressure checked?
Click to expand...
to be honest I don't know where it's coming from. It only bubbled with 5psi and didn't leak at all sitting at night. I'm wondering if I'll even have a problem using it before I get the new ones Just for 1 test ride. With the motor running it would blow out the exhaust. Shut it down it would drain out the manifold anyway. When I left the water in the elbow overnight there never was a leak. I know i need them, but may be over thinking this.
 
Don't do it, sediment is most likely blocking the tiny hole in the weld. On the photo I attached that elbow didn't leak sitting overnight filled with water, not a single drop. Then I shook it and pressurized to 10 psi and the little stream of water appeared. I then put it in a 200°F oven and the water really started flowing.
 
mnm99 said:
Just a FYI...NOBODY has them:mad:. I just returned the wrong ones. Went to order the new ones since they did say in stock. Turns out there not. Nobody has them and merc says mid to end of May! i'm a little pissed to say the least. Just put the boat in the water on Saturday...
Click to expand...

Yup just found that out this morning..............
Also was warned that that is the best-case as my marina parts guy said they have had orders take double the predicted time.

I haven't returned them yet, going to make some measurements tomorrow.
Perusing the Mercury "GASOLINE ENGINE 8.1S INBOARD MODELS INSTALLATION MANUAL" I need at least 15 inches from the fully loaded waterline to the top of the elbow with water lift mufflers.

Of course nothing is simple, the "Mercury Product Applications Manual for Gas Inboard Models" states riser height for systems using a water lift muffler -> "measured to the water line in the muffler" must be at least 15 inches.

I will report back what I measure.

Anyone reading this with a 340 w/ 8.1s have standard elbows???

-Chris
 
NEpilot said:
Yup just found that out this morning..............
Also was warned that that is the best-case as my marina parts guy said they have had orders take double the predicted time.

I haven't returned them yet, going to make some measurements tomorrow.
Perusing the Mercury "GASOLINE ENGINE 8.1S INBOARD MODELS INSTALLATION MANUAL" I need at least 15 inches from the fully loaded waterline to the top of the elbow with water lift mufflers.

Of course nothing is simple, the "Mercury Product Applications Manual for Gas Inboard Models" states riser height for systems using a water lift muffler -> "measured to the water line in the muffler" must be at least 15 inches.

I will report back what I measure.

Anyone reading this with a 340 w/ 8.1s have standard elbows???

-Chris
Click to expand...
Let me know.
 
Good thing you were on the ball. That 8.1 is one expensive engine!
 
RiserHeightSpec1.png RiserHeightSpec2.png

I made the measurements last night...

To violate the Mercruiser rules using "standard elbows" the water level in the lift mufflers would have to come within an inch of the top of them. The angle in the exhaust tubes with the 2" elbows is 22° compared to 15° using the standard elbows.

On my boat this means I would have to load it ( somehow ) to sit 6" deeper in the water.

So I am left wondering why Sea Ray has such a huge engineering factor on the elbow height? Also interesting is my port lift muffler is set back 4" further than the starboard side.

Now I have a big decision to make, believe my data or give up a month of my season.
 
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