Hi Jason
This was a commercial decision for the type 915 and 916 engines. The type 912IS they are the standard rubber. (you would have to request the option in that case or fit them after) All the versions were the ASTM versions. This is the same for fuel pumps for the type 915 and 916. From Rotax they are a separate cost, not included in the price. There are a few distributors like in the Americas, the pumps are added to the cost and supply scope rather than an option. Before the type 915 came out Rotax did not have any option for silicone coolant hoses. This was extended to the type 916 as well.
If you got it from the Canadian distributor I am pretty sure it is optional for those engines at time of order. Certified engines take a long time to get imported as they are normally only custom order. Some distributors, like Rotech Motor in Canada, have inventory of engines. Others only import on order. Rotax-Owner might comment on that point.
Cheers
