New sailors rarely raise sails correctly and it may be that in not raising these sails fully the boom is not raising properly causing the boom to ride lower than the 'intended design'.
Assuming that you have sails made of dacron polyester on 52 ft. masts. would indicate that the luff of the sail would be in the range of about 46 ft.
Next time, try raising the sails in the following manner: Raise the sails, then apply an additional approximate 5 inches of 'stretch' with the halyard ... the boom end shoud raise approximately 5+ inches.
If the sail is made from dacron polyester and has a 'rope' in a sleeve at the luff, this rope has to be stretched by about 1" for every 12" of luff length. The rope in the sleeve at the luff is callled a 'boltrope' and when making the sail the sailmaker will purposely cut the rope shorter (1" for every 12" of luff length - call 'preload') so that the sail will be stable when fully wind loaded at its usual maximum wind range of 15-18 knots. If you dont stretch out this preload, the sail wont be fully raised and the boom end will be much lower than the design. Applying the correct halyard tension will raise the boom end .... and you may have the desired 'clearance' beneath the boom --- simply by raising the sail correctly.
If this is an old, well used sail it may be that the boltrope has simply shrunken (and become fatter) as every time you raise and then relax the luff this three strand rope becomes shorter. If so, you can take the sail to a sailmaker to 'ease' the boltrope; then, when raising the sail to the correct halyard tension the boom end will be much higher because the 'head' of the sail will be able to be raised higher on the mast !!!!! Raise the sail and with the winch 'crank' an additional 5-6 inches of halyard after the sail is 'up' .... I'll bet that the problem is that you are not applying sufficient halyard tension and this causes the boom to be much lower than the original design.