Abstract: A ram tensioner system with a deck mountable frame having an upper portion and a lower portion connected by a plurality of cylinder sleeves and at least one guide post sleeve. A guide post engages the guide post sleeves, and an individually replaceable modular cylinder is in each cylinder sleeve along with at least one individually removable seal gland that is lubricated by a hydraulic power unit, and a slidable rod engaging each of the cylinders. The slidable rods can be attached to the tension deck with a tension ring to engage a riser and provide movable tension to the riser.