Sorry, it was a typo!
The following SAP BC extend value is : watt.sap.xml.encoding=utf-8
The xml file i get from SAP CRM is also: <?xml version="1.0" encoding="utf-8" ?>
The flow service: StringToDocument (Encoding) is utf-8
We get the CRM catalogue via a routing rule in SAP BC (wm.PartnerMgr.flows.XMLCatalog.SBCCCD:XMLCatalog) which than call a specific flow service (that do the main tasks).
The values (é,è, etc) are ok in the CRM catalogue. As soon as i get it in SAP BC, i loose the french accent …
Thank for your help ! 
#webMethods#Integration-Server-and-ESB#Adapters-and-E-Standards