Male marking

I have owned and bred maltese for about 25 years, bought our first in England in 1973. Have a problem I have never had to deal with before. I recently became owner of a very nice male maltese who has been used for a couple years as stud. He has a wonderful pedigree and has been well trained so is pretty easy to live with, but he has been crated whenever he is in the house. He is the only male I have here and I would Like to allow him loose in the house sometimes(they all sleep in crates at nite to prevent roaming and accidents) he doesnt mark in his crate, but the minute he pauses next to anything on his side he lifts his leg and marks. Is it to late to train him to be in the house loose, and if not, how do I do it. Thank you to anyone with any suggestions.
Pam

• Temporary diapering works well on most boys, they don't like getting themselves wet. Make a multi layered band of soft absorbant material approx 3 inches wide (dependent on size of male) and long enough to wrap around him snugly. Velcro works well as fastener so diaper can't move around. Some boys figure it out quick, some may need a month. If you also have females bring the diapers out as a reminder when one of them is due in season.
  Sylvia