1 to 3 mm is not an issue. Go with what SG said. Inspect the mounts for condition and that they are securely mounted. Remember that the engine mounts are transferring all of the thrust and torque developed by the engine - that is, unless you do have a CV. Even with a CV the engine will twist from the torque and with a CV the mounts can be much softer (by design for less noise transfer to hull) and there can be even more movement.