The historic Cathedral of the Immaculate Conception on Congress Street will play host to Friday’s installation of Bishop Robert Deeley as the 12th bishop of the Roman Catholic Diocese of Portland.

The ticketed event begins at 2 p.m. and is expected to draw more than 800 people, including three of Maine’s last four bishops, 30 other bishops from across the country and Archbishop Carlo Maria Vigano, the apostolic nuncio to the United States, better known as Pope Francis’ U.S. representative.

Cardinal Sean O’Malley, archbishop of the Boston diocese, will preside over the installation and Mass, an event filled with Catholic tradition and pageantry.

Deeley will honor the Portland diocese’s history by using the crosier – the pastoral staff carried by a bishop – that belonged to David W. Bacon, Maine’s first Catholic bishop. After the installation, Deeley will deliver remarks similar to an inaugural address.

Monsignor Michael Henchal of St. Maximilian Kolbe in Scarborough said he has known Deeley since they were in school together in the late 1960s and early 1970s but has never heard him preach.

“I think a lot of people are curious,” Henchal said Thursday. “There is a sense that the diocese has been sort of drifting and waiting for a new direction.”

Maine is home to 193,392 Catholics, or about 1 of every 7 residents, according to the diocese. Catholicism is still the largest religious block in Maine, although its numbers have dropped considerably. From 2000 to 2010, the church lost 90,000 adherents, or about one-third of its members.

As bishop, Deeley will oversee the ministerial and administrative duties of the diocese, presiding over 55 parishes across the entire state and leading 60 active priests and 39 lay ministers.

Deeley, 67, was ordained as a priest in July 1973 and spent his first five years at Saint Bartholomew Parish in Needham, Mass. He also has served in Newton, Lexington and Wollaston, all in Massachusetts, and spent seven years at the Vatican. Deeley became a monsignor in 1995 and then was appointed auxiliary bishop of Boston in January 2013.

He succeeds Bishop Richard Malone, who has served as head of the Portland diocese since 2004.

In May 2012, the pope appointed Malone to lead the diocese of Buffalo, N.Y., a much bigger district than Maine’s. Malone has split his time between New York and Maine since.

Like Deeley, Malone spent most of his time in Massachusetts prior to coming to Maine, including service under Cardinal Bernard Law, one of the major figures in the church sex abuse scandal that gripped the church a decade ago.

Malone was often criticized for his role in handling Maine priests suspected of abuse, even though few, if any, abuse incidents occurred under his watch. He also was criticized by some Catholics for his prominent role in the successful 2009 people’s veto referendum to overturn a same-sex marriage law. Three years later, when supporters of same-sex marriage initiated a new referendum, the church and Malone mostly stayed on the sidelines. The law passed.

Malone also was responsible for the consolidation of Maine parishes from 135 to about 60, a shift needed both to address declining church membership and a shortage of priests.

Deeley takes over at a time when fewer young Catholics are coming into the church, many because they disagree with its conservative stance on social issues.

Henchal said he expects the new bishop to spend the first few months meeting with his priests and touring the state before outlining his priorities.

Maine has had 11 bishops since the diocese was created in 1855. The longest tenure was that of Maine’s second bishop, James Augustine Healy, who served from 1875 to 1900. The shortest stint was that of Peter Leo Gerety, Maine’s eighth bishop, who served from 1969 to 1974 before being appointed archbishop in Newark, N.J.

Gerety, now retired, is the oldest Catholic bishop in the United States at age 101. He is expected to join Malone and Joseph J. Gerry, Maine’s bishop from 1988 to 2004, at Deeley’s installation Friday.

Every Maine bishop except Bacon, the first, has been installed at the Cathedral of the Immaculate Conception. Bacon is buried in the crypt beneath the church.

The 145-year-old cathedral is steeped in history and has been on the National Register of Historic Places since 1985. Among the cathedral’s features is its 3,336-pipe organ, which was built by the Henry Erben Co. of New York and is as old as the church.

The Mass will be televised live on EWTN, the Catholic television network, available throughout Maine.

The ceremony may also be viewed online at www.CatholicTV.com/watch-live and will be broadcast on several radio stations, including the Presence Radio Network (106.7 FM in Greater Portland).

Staff Writer Eric Russell can be contacted at 791-6344 or at: erussell@pressherald.com

Twitter: @PPHEricRussell