Edit ~/.subversion/config, section [tunnels], example, port 2222 and 12345:
[tunnels] ssht = ssh -p 2222 sshtunnel = ssh -p 12345
Then use svn+ssht://domain.tld and svn+sshtunnel://domain.tld instead of svn+ssh://domain.tld
Source: http://www.techper.net/2009/01/11/changing-port-number-of-svnssh-subversion-protocol/