Exhaust problem

[roberttigar]

I have an exhaust system for my Perkins 4-108 with a stand-pipe. The 3" line from the exhaust manifold to the stand pipe has deteriorate where the flex pipe meets the straight pipe.

I'm going to replace the whole section, but I would like a better solution than using flex pipe as it is a thinner -walled than the straight pipes.

I hit on the solution of using flexible silicone ,like "Blue Nautiflex". But these specify "wet exhaust" applications. There is also red silicone available for higher temps. I realize that dry exhaust is a higher temp that wet, but what else is the different? Bob

[GordMay]

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High Temperature Exhaust Hose Color Comparison [Trident]
• Black exhaust hoses: made from molded, high temperature, black EPDM rubber. Rated -40°F to +250°F maximum continuous, with a 5-year warranty
• Blue exhaust hoses: made from a very high temperature, blue silicone rubber. Rated -65°F to +350°F maximum continuous, with a 10-year warranty
• Red exhaust hoses: made from an extra high temperature, red silicone rubber. Rated -65°F to +500°F maximum continuous, with a 10-year warranty
More about ➥ https://www.fisheriessupply.com/trid...double-bellows

[PippaB]

Using Gord’s info and comparing with Perkins saying that maximum EGT (exhaust gas temperature) for the 4-108 is 670C (1200F, at full rated output, which most boats rarely reach) and you’ll see why a metal bellows was used. Even at economy cruising speeds typical diesel EGT is 260 to 430C (500-800F). Depends on where in the exhaust and how much it has cooled by the time it reaches the flexible section, but you’ll likely be running red silicone at or above its maximum rated temperature.