I would ditto of what bobby says about taking care of your tackle believe me I am now a different person after my two initial reels were destroyed because my carelessness a Diawa and a Mitchell from sea water. Please don't wait do it immediately once you return home from fishing the saltwater is really a dangerous thing for your tackle. It takes only ten min but it will save your precious tackle for a life time I even wash my lures thoroughly once i come back from a trip.
I think you can write to a Okuma dealer near you or see on e bay and replace the drag system of your reel.
I have yet not caught a very big fish from the beach but I think the okuma 4000 series sound a small reel for the beach casting you should have at least a reel which will hold 250 Yrds or so of 30 Lb line even if it means using a heavy reel for minimum . I use a Okuma avenger 80A reel with 30 LB line and a mono leader of 50 Lb double strained for targeting the Shark and all . I although have not yet got big one as yet as I hardly have tried it outside Mumbai where you don't get any fish in beaches.
Although last time we landed a big stingray and believe me it took almost all the strength of Ali's rod and reel which is almost a similar set up like mine to land that one .
I was glad to see that because it really strengthen my believe on the minimum tackle you should have while beach fishing
I wish you all the best for the next big one