One of the requirements for the bellows is to resist the twisting force from the prop shaft rotation. I suspect PYI and their suppliers have looked at many materials and manufacturing techniques to find the best compromise between strength and flexibility with an eye for cost.
IIRC back in the 80's when I put my first PYI Shaft Seal on a boat the bellows had an outside texture more like a fabric. The one on Calypso today seems smoother and more like a polymer or silicone based material. I am careful with both mechanical and chemical exposures around the bellows. If the boat has been sitting un-used for more than 6 weeks I will give the bellows an inspection and "burp" to be sure no growth has bonded the rotator to the carbon bushing at the end of the bellows. Likely this is overkill but I am within a foot of the bellows when opening the raw water through hull valve. Martin Calypso 1971 C&C 43 Seattle From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Bill Coleman Sent: Thursday, November 14, 2013 7:15 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List further questions about replacing the bellows on a PYI shaft seal You would think, but I don't see it on their site, just the rubber one. Besides, if they did, it would ruin their aftermarket for replacements! Bill Coleman C&C 39 From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Rich Knowles Sent: Thursday, November 14, 2013 9:57 AM To: cnc-list@cnc-list.com<mailto:cnc-list@cnc-list.com> Subject: Re: Stus-List further questions about replacing the bellows on a PYI shaft seal PYI must have considered this..? Rich On Nov 14, 2013, at 10:43, "Bill Coleman" <colt...@verizon.net<mailto:colt...@verizon.net>> wrote: Has anyone ever seen a Silicone bellows, or similar that could be used for this? I am a big fan of silicone hose, and have seen short connectors on powerboats with a pleat in the middle, but not multiple pleats. I have also seen a picture of a silicone (I think) bellows on European boat. Bill Coleman C&C 39 <image001.gif>
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