Elbow Replacement

Getting to the 5 year mark where I am going to be changing the manifolds. As we all know with the 8.1s its a few boat dollars and the question whether to inspect the elbows and not replace due to them being Stainless comes up. I asked a very reputable mechanic and he said to replace the elbows with the manifolds as the weld at the plate could fail due to heat and create salt water to leak back to the engine. I see numerous posts where the elbows are just inspected and placed back on motor. My gut is saying to just replace but wanted to get some more feedback as other mechanics have told me they are good for a few more more years.
THanks

I replaced mine @ 15 years (in 100% saltwater) just for peace of mind. If you are already in there doing the manifolds, the elbows are no more investment in time. I also stenciled the manifold and elbow so I (or the next owner) was sure when they were replaced last. Like the manifolds, you will get almost no indication of imminent failure. They generally will start corroding and pitting internally (at the weld, like the mechanic said) and leak back into your exhaust ports after shutdown.

I replaced my elbows last year at 14 years.

As per the above post there had been a few reports on this forum of pinholes developing at the weld and so I also thought cheap insurance since I was having the manifolds replaced as well.

dino said:

Getting to the 5 year mark where I am going to be changing the manifolds. As we all know with the 8.1s its a few boat dollars and the question whether to inspect the elbows and not replace due to them being Stainless comes up. I asked a very reputable mechanic and he said to replace the elbows with the manifolds as the weld at the plate could fail due to heat and create salt water to leak back to the engine. I see numerous posts where the elbows are just inspected and placed back on motor. My gut is saying to just replace but wanted to get some more feedback as other mechanics have told me they are good for a few more more years.
THanks

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This exact thing happened to my friend, He had to rebuild the heads due to bad weld on the SS elbows.
It took him a long time to figure were the salt water was coming from.

Replaced one on my old boat. Sure as $hit pin hole on the bottom weld. It drips and is captured by the tubilator. That joint is a dry joint so if and over time the tubilator fails it's job, water can run down the hole to the mid and aft cylinders. You don't notice it because when you start the engine it evaporats almost instantly. About 5 table spoons of water can sit in there after the engine is off. Only sign if lucky is a drip rust line on the outer inboard side of the riser joint. A place at a glance you'd not see unless you force a look with a flashlight.
Test the riser on a bench. Take the two 90 degree hoses and turn them up. Put the riser on a paper towel and fill with water until full. Sit 24 hours. If towel is dry, good to go. If you find a drip or two then toss! Bummer part those silly parts are near 800 bucks each. And supply is limited. Again, that joint (manifold to riser) is a dry joint. Keep an eye for any rust lines. You'll never see water because that area is hot and drys faster than the leak. Just the rust line is left over time. You see that, then 99% there is a leak.

So why does this happen... I have a theory. It only takes one time, but if you start the boat and there is no water flow, bad impeller or the petcock was closed. That joint super heats in a matter of seconds. Degrading the joint. If you happen to forget about the petcock closed and then shut down because you remembered, DON'T START start the engine until that joint cools. You know what happens when cold hits Hot! The weakest area fractures... I think that's what happened to mine.

Boats, got to love the learning lessons... $$$

Thanks for the replies! Think I am going to go ahead with manifolds and inspect the elbows. Ill keep an eye on them and replace in couple years to be safe.