Сравнение

Ship/Ship/DrawingObject.cs

@@ -40,5 +40,34 @@ namespace Ship
         public string GetInfo() => _ship?.GetDataForSave();
 
         public static IDrawingObject Create(string data) => new DrawingObject(data.CreateDrawingShip());
+
+        public bool Equals(IDrawingObject? other)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+            var otherCar = other as DrawingObject;
+            if (otherCar == null)
+            {
+                return false;
+            }
+            var car = _ship.Ship;
+            var otherCarCar = otherCar._ship.Ship;
+            if (car.Speed != otherCarCar.Speed)
+            {
+                return false;
+            }
+            if (car.Weight != otherCarCar.Weight)
+            {
+                return false;
+            }
+            if (car.BodyColor != otherCarCar.BodyColor)
+            {
+                return false;
+            }
+            // TODO доделать проверки в случае продвинутого объекта
+            return true;
+        }
     }
 }

Ship/Ship/IDrawingObject.cs

@@ -6,7 +6,7 @@ using System.Threading.Tasks;
 
 namespace Ship
 {
-    internal interface IDrawingObject
+    internal interface IDrawingObject : IEquatable<IDrawingObject>
     {
 		/// <summary>
 		/// Шаг перемещения объекта

Ship/Ship/MapWithSetShipsGeneric.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 namespace Ship
 {
     internal class MapWithSetShipsGeneric<T, U>
-        where T : class, IDrawingObject
+        where T : class, IDrawingObject, IEquatable<T>
         where U : AbstractMap
     {
         /// <summary>

Ship/Ship/SetShipsGeneric.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 namespace Ship
 {
     internal class SetShipsGeneric<T>
-        where T: class
+        where T: class, IEquatable<T>
     {
         /// <summary>
         /// Массив объектов, которые храним
@@ -45,6 +45,11 @@ namespace Ship
         /// <returns></returns>
         public int Insert(T ship, int position)
         {
+            if (_places.Contains(ship))
+            {
+                return -1;
+            }
+
             if (Count == _maxCount)
             {
                 throw new StorageOverflowException(_maxCount);