multiple version installation in the same machine ????

Hi
I have a postgres version 7.4 and version 8.3 installed in my system.
7.4 uses port 5432 and 8.3 uses port 5433.
I started 7.4 and the database is running fine. Now i started the database
server in version 8.3
and it started fine.

pg_ctl -D /export/home/josh/postgres8.3/pgsql/data start -l log8.3.log
server starting
-sh-3.00$ pg_ctl status
pg_ctl: server is running (PID: 4408)
/usr4/postgres8.3/bin/postgres -D /export/home/josh/postgres8.3/pgsql/data

But when I type psql -l I get this error
-sh-3.00$ psql -l
psql: FATAL: database "postgres" does not exist

why? Is it not possible to have multiple version installations i the same
machine(in different ports)?

thanks
josh