Weld Still in Service
In response to your note:I had that piece welded about 4 years ago, and its still going strong. I would caution you, though, on the muffler and the aluminum flexible hose. If the whole hose is rotted, just replace it with a comparable one; its a 10 minute job. If just the end is degraded, cut it off and if you have enough "loop" in it, just move it forward onto the manifold. The exhaust hose carries both water and exhaust (the engine cooling raw water gets injected right before the hose clamp on the manifold). As a result, its wet and a prime site for gavanic corrosion if you place two dissimilar metals together (i.e. steel and aluminum). That repaired manifold will be rusted out in no time flat if you connect an Al hose to it (hey, occasionally having a PhD in Metallurgy comes in handy!). The steel wire reinforced rubber exhaust hose will last you 20 years. Same holds for the "muffler", which is really more of a can where that exhaust cooling raw water accumulates before its burped out with the exhaust. Don't replace it unless its leaking. If it is, then buy a new one. I wouldn't mess with automotive mild steel on that; its most likely stainless steel. Remember that the exhaust system on a marine diesel has two functions - get rid of the exhaust but also cool it down so it doesn't melt anything (diesel exhaust can be upwards of 1000 F). Hint for avoiding corrosion: flush the engine with fresh water before you leave - use the T junction at your raw water inlet. If you don't have one, put one in; you'll need it to antifreeze the engine this winter anyway.Good luck with it. Remember that you should change the engine zinc and the secondary fuel filter about once a year, and for those you WILL need genuine Renault parts. As Renault Marine got bought out by Nanni in the '80s, that second web site I sent is the one to check out. The Texas folks went out of business a year or two ago - the other folks (Lauderdale Marine, I think) are in Miami.