Not really, you can stop the boinc-deamon (startup script) via this:
sudo gedit /etc/init.d/boinc-client
Type password and press enter, change the top ENABLE from ''0'' to ''1''
Problem is, when starting the boinc manager it will not be able to connect to the boinc client because it's not running. In Windows the client will start with the manager, in Linux not. I don't know how to start the boinc-client manually.
sudo /etc/init.d/boinc-client start
does not seem to work for me, only the restart function works.