If anything, turrets should have a smaller range than a warship's.
In the 1600's or whatever era, a warship could easily stay out of range and bomb coastal fortifications, turrets in this case. Turrets would have 1-2 range and could take out transports and other ships if turrets are not destroyed beforehand.
This would allow the defender more time to come up with a counterattack against the warships, and the attacker would need to protect their warships from the counterattack. It'll create a much bigger impact on naval warfare.
Thus, the same range would be applied on land, however there is no land unit with the same ability as a warship, so it's just storming a turret with enough units that the turret can't target them all. (Reasonable to say one turret can target once per Cycle, and is not overpowered in any sense) One could simply send two L9 infantry and push around the turret, one of them would get wounded but ultimately can still ignore the turret and advance on. However 5 turrets in a line would certainly make more of an impact and may encourage attackers to remove those turrets.