I don't know what makes you post this to the JCA forums , this should be asked in the Transaction forums .
Coming to your question you can try few things
1) Have you tried setting the timeout at the component level ie changing timeout setting in the jboss-service.xml in the EJB ?
2) You can explicitily set the transaction timeout value in some application specific configuration file which will later be used by UserTransaction.setTransactionTimeout(..)
In this case you will be using Application Managed Transaction