Any system/OS can only ever have one default gateway at a time. It's a bad Windows-habit that you can supposedly configure a "default gateway" for each NIC, but that doesn't make any routing-sense.
Only use a default gateway on your management vmkernel port. You do not need to specify a default gateway on your vMotion vmkernel ports, and you shouldn't route this subnet in the first place.
For vMotion just use a separate, isolated VLAN with a separate IP subnet (anything private goes as long as your ESXi management interface won't need to communicate with systems in a "real" subnet on your network) without any router present.