error CS1503: Argument `#1' cannot convert `object' expression to type `UnityEngine.Vector3'

trying to setup a sphere cast to see when a object is in range of my turret

getting
error CS1503: Argument #1' cannot convert object’ expression to type `UnityEngine.Vector3’

using UnityEngine;
using System.Collections;
public class TurretScript : MonoBehaviour {


	public GameObject Target;
	public GameObject MachGuns;

	public bool AllyTurret;
	private bool Aiming;
	private bool IsFireing;
	private bool AssignTarget;
	private float Distance;
	public float FireRate = 1f;
	public AudioClip Gunz; 
	public float Ammo = 80;
	public float turnspeed = 12;

	//--------------------------------------------------------------------
	// Update is called once per frame

	void Start(){
		if (AllyTurret == false) {
			Targets = GameObject.FindGameObjectsWithTag ("BlueTeam_Fighter");
			index = Random.Range (0, Targets.Length);
			Target = Targets [index];
		}
	}

	 void Update () {
		
		if (Target != null) {
			Aiming = true;
		}

	
		if (AssignTarget == true) {
			IsFireing = true;
		}



		if (IsFireing == ture) {
			MachGuns.SetActive (true);

		} else {
			MachGuns.SetActive (false);
		}


		if (Aiming == true) {
			TurretGuns.transform.rotation = Quaternion.Slerp( TurretGuns.transform.rotation, Quaternion.LookRotation(Target.transform.position - transform.position ), Time.deltaTime * turnspeed);

		}

		//------------------------------------------------------------------------------


		RaycastHit hit;

		if (AllyTurret == false && Target == null && AssignTarget == false) {
			if (Physics.SphereCast (gameobject.transform.position, 1f, gameObject.transform.forward, out hit, 50)) {
				if (hit.collider.tag != "Blue_Team_Fighter") {
					Target = hit;
					AssignTarget = true;
				}
			}
		}

		//------------------------------------------------------------------------------


		if (AllyTurret == true && Target == null && AssignTarget == false) {
			if (Physics.SphereCast (gameobject.transform.position, 1f, gameObject.transform.forward, out hit, 50)) {
				if (hit.collider.tag != "Red_Team_Fighter") {
					Target = hit;
					AssignTarget = true;
				}
			}
		}


		//------------------------------------------------------------------------------



	// DISANCE:
		Distance  = Vector3.Distance(Target.position, transform.position);
		if (Distance > 50) {
			Target = null;

		}


			}

}

You might have made a typo ‘gameobject’ instead of ‘gameObject’, but I doubt that is the real issue.