That metal cylinder is part of a bronze casting that becomes the cutlass bearing housing just behind the deadwood.
I would consider leaking around the shaft tube a pretty serious but not immediate problem. The next time you haul out for a bottom job, the whole bronze casting should be removed, cleaned, dried out and rebedded.
So now you have caused me to take a look at my 10 year old Pilot 34! I will let you know what I find. Modern caulking should last more than 10 years.