SOLVED

The following works !

I guess one of my others rules was blocking

table ip Tip {
        chain prerouting {
                type nat hook prerouting priority -100; policy accept;
                ip daddr 192.168.y.2 log prefix "forwarded " dnat to 192.168.y.3
        }
        chain postrouting {
                type nat hook postrouting priority 100; policy accept;
                masquerade
        }
        chain INPUT {
                type filter hook input priority filter; policy accept;
        }
        chain FORWARD {
                type filter hook forward priority filter; policy accept;
        }
        chain OUTPUT {
                type filter hook output priority filter; policy accept;
        }
}