In 1815 his mother, now widowed, married Captain Charles Napier, the future admiral, who adopted her children as his own and gave them his name in addition to Elers.
When his stepfather's flagship came alongside the Miguelite ship-of-the-line Rainha, Elers Napier and one other officer were the first to board her and were then cut off as the ships yawed apart.
After he recovered he was appointed by his father to command of the sloop Portuense, and then to the corvette Sibylle, in which he sailed to Madeira to demand the surrender of the Miguelite governor.
Being superseded in this command he was on shore in China for a period and then became aide-de-camp to Admiral Sir William Parker, taking part with him in the capture of Zhenjiang by scaling the walls on 21 July 1842.
[2] In late 1847, having been made post captain, he was appointed to the command of the steam frigate HMS Avenger, joining her at Lisbon, but had been in her only a few weeks when, having left Gibraltar on course for Malta, she was wrecked at night in foul weather on the Sorelle Rocks off the island of Galita, with the loss of all but eight of her complement.