This page (http://www.usmm.org/killed/h.html), listing World War II U.S. merchant marine casualties with last names beginning "H," shows 16 men named Harris and 12 named Harrison. Several died in 1945 but the information here is not specific enough to determine the cause of death or the location of the ship. One had an on-board assignment that could have placed him in the engine room (2nd engineer in the case of Harry Harris, killed 4/9/45 aboard SS CHARLES HENDERSON). But in a boiler explosion crewmen other than engine room personnel could have been killed.
From this page (http://www.usmm.org/sunkaz.html#anchor9484) one can see that CHARLES HENDERSON sank in the Mediterranean or Black Seas due to an explosion. (The ship actually sank in Bari, Italy, when its cargo of bombs exploded.) You speculate the loss may have been off Estavan Point, which is in British Columbia, so that's not a match.
This page (http://www.usmm.org/pacific.html#anchor444903) lists ships that sank or were damaged along the "Westcoast" which presumably would include British Columbia. But only one ship sank in 1945 in that very general area, and due to a collision, not an explosion.
There are lists of men of the Canadian armed services (known collectively as the Books of Remembrance), specifically the Canadian Merchant Navy in this case, who died in World War II at http://www.vac-acc.gc.ca/remembers/sub.cfm?source=collections/books/bmerchant/merww2nahttp://www.vac-acc.gc.ca/remembers/sub.cfm?source=collections/books/bmerchant/merww2na. There are three named Harris and one named Harrison, none of whom died in 1945. They are listed by name of ship and date but other details are sketchy.
A more inclusive listing in the Book of Remembrance for World War II deaths in 1945, regardless of military service, is at http://www.vac-acc.gc.ca/remembers/sub.cfm?source=collections/books/bww2/page1945http://www.vac-acc.gc.ca/remembers/sub.cfm?source=collections/books/bww2/page1945. Again there are several men named Harris (7) or Harrison (9) but none seem to have been in the Royal Canadian Navy. Again details are sketchy.
So, no matches for your information, assuming what you have is reasonably accurate.