I am looking to extend a set of risers that I have on my boat right now. I am needing 316 stainless 3.5" OD and 4" OD tubing and somehow coming up short finding it at a semi reasonable price. Does anyone know a good place to order from? Or is there a specific industry that uses this? I work in a industry that we use a ton of pipe but nothing this thin so we are coming up short on tracking it down. It seems 304 stainless is a little more common but everything I have read says 316 is the best for this application. I need 6-8 feet of each. Thanks for any help in advance

Not sure of the alloy, but I have purchased the tubing a few times from the local performance exhaust shop and it has worked fine.

I have seen the 304 stainless from local places. The 316 seems a bit tougher to get. I need to do some more research and see if there is even a big enough difference to matter. Thanks

We have 4" polished and 3.5 raw but it's 304 SS.

If you're not boating in salt it doesn't really matter, 304 will be fine. 316 has molybdenum to better resist corrosion to chlorides like salt. If you think you need 316, you could search for food-grade tubing, Mcmaster Carr has some but it isn't cheap.

I got mine, inner and outer (outer polished) off ebay pretty reasonably

We do not boat in salt but hope to in the future. If we do, it will a week tops and happen maybe if we are lucky once every few years. If the 304 is ok, that is a ton easier and cheaper to get

Woolf Aircraft Products , Romulus Mich. I buy all my tube from them , most all risers and tailpipes are 304.

Most I have seen are 316L from what I have seen. CMI, Stainless marine and hardin are all 316 which was backing the claim that I needed it. I did see that Imco is 304 though and I have never seen their risers have issues. I think I will be ok with the 304. If not I guess I will go back with the 316 later on. I will check with Woolf before I order anything.

Thanks for the help everyone

I used 304 from Vibrant Performance for custom risers, I use 316 as the filler rod and purge them correctly. Never had them rust out or leak to date, the oldest set is around 7 years old now and still going strong. Food grade was the only 316 I could find I did buy a 20 foot length of 4" and it was $600 CAD.