What type of rubber is used for sterndrive bellows and what is their shelf-life?

Well, the whole question is in the title?

I am asking this because I would like to know if it has sense to buy a couple of them for spare which can last a long time, but will the material keep its properties?

 

Not too sure on the shelf life... Assuming you don't lose a universal and all is correct they're good for quite some time in service. I've seen them 10 years old+.
What manufacturer are you running?

 

Not really sure. I'd rather have bellows as new as possible. Would buy one set at a time. Could be 5 or 6 years before you change again.

 

I am running a bit older type - SternPowr model 103, that is the main reason why I ask for the shelf life, because I do not know how long it will be available so I thought of buying a few more for spare. And for the material I ask so I can custom build it somewhere when it becomes unavailable. I could not find any other brand model bellow that matches with the model I own (maybe anybody here knows some?). I have a trouble-free experience with my first bellow for three years now, controlling it each year out of the water. Thank you for the first answers.

 

I found this on an older post in another forum:

Stern Powr was made by Marine Drive systems. They made 101, 103, 105 and MX-07 drives. The company was bought by Sherwood Propulsion systems in '02. They manufacture all parts for the old drives. Call 888-322-7697 and talk with Doug or Wayne.

It's from an archive (2005-2006) Perhaps this will guide you to a resource.