Backstay tension

[marcot]

My Hr48 is fitted with an Holmatro hydraulic backstay tension pump. After 6 years of moderate cruising (mainly the Med and a northern Europe cruise) , when pumping up to 3000kg, the forestay (hydraulic Selden system) is very slack. What can I do? Backstay is 12 mm

 

[William_H]

How slack is very slack for a forestay. It is almost inevitable that the forestay will have some curve to leeward when driving hard.
However assuming you mean really slack ie obviously not being tensioned then either the ram on the backstay is bottoming out ie run out of movement or less likely the mast is being pulled forward by a tight inner forestay or possibly twin forestays.
To get that pressure something has hit a wall. I doubt it is the jib halyard tension itself. Sorry needs investigation and or more detail.
my guess though is the ram has bottomed out at full travel. good luck olewill