It is possible to change the OID ports from the Enterprise manager console. Unfortunately, after changing the ports, EM will not be able to change server properties like ports (!).
After changing the ports, an OPMN command must be run to update EM with the right settings:
$ORACLE_INSTANCE/bin/opmnctl updatecomponentregistration -componentType OID -componentName oid1 -adminHost myoidhostname -adminPort 7001 -adminUsername weblogic -Port 3060 -Sport 3131
(change parameters as suited and restart OPMN)
If you are using DIP (Directory Integration Platform) as well, you will have to change the (SSL) port accordingly in …../config/fmwconfig/servers/wls_ods1/applications/DIP_220.127.116.11.0/configuration/dip-config.xml