transform.rotation Local Axis

I need to rotate my object around Y axis, and im doing it(like a tank tower). But only in global coords. When my object rotating itself (spaceship for example) my object still rotation around global Y.

 using UnityEngine;
 using System.Collections;
 
 public class subTowerControl : MonoBehaviour
 {
     //public float rotationSpeed;
     //public float targetingDistance;
 
     void Start()
     {
 
     }
 
 
     void Update()
     {
         towerRotation();
     }
     void towerRotation()
     {
 
         var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
 
         RaycastHit hit;
         if (Physics.Raycast(ray, out hit, Mathf.Infinity))
         {
             Debug.Log(hit.point);
             Vector3 targetPoint = hit.point;
             //Vector3 targetPoint = ray.origin + ray.direction;
             var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
             targetRotation.x = 0.0f;
             targetRotation.z = 0.0f;
             transform.rotation = Quaternion.Lerp(transform.rotation, targetRotation, 2f * Time.deltaTime);
         }
         else
         {
             var targetPoint = ray.origin + ray.direction * targetingDistance;
             var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
             targetRotation.x = 0.0f;
             targetRotation.z = 0.0f;
             transform.rotation = Quaternion.Lerp(transform.rotation, targetRotation, 2f * Time.deltaTime);
         }
     }
 }