Dear Matt,
Probably the sealing "rubber" is not inside the "trench" .
So, this will do big leakage when the pump increase his speed.
You have to stop, open the cover and place very carfully the seal (it is not easy with big fingers
).
after this, place the cover and torque the screw a little at each time (not full torque or you take the risk to put out the seal again).
Check at the end that all screw are well torque.
Good luck and enjoy ,
Steff.