The stainless rivets that hold the end cap on have most likely corroded(Galvanic Reaction) with the aluminum making the cap hard to get off. I had to use a large screwdriver and a hammer with large amounts of penetrating oil to get mine loose a few years back.Use the screwdriver like a dull chisel to tap around the end cap. Just be careful you don't break the casting.
Todd


"I said, now, I said ,pay attention boy!"

The cure for anything is salt water - sweat, tears, or the sea
Isak Dinesen
If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most.
E. B. White