Submarine chaser SC 282 was commissioned at Mare Island on 22 April 1918, and served in the Canal Zone.
These photographs are from the collection a crewman on SC 282, and were submitted by his grandson, Mike Stephenson. Note especially the exceptional shot of the wheelhouse, possibly the best one I've seen.
The Y-Gun photo shows the detail nicely: A blank charge would be inserted at the base, to launch the two depth charges.
The photo showing chasers with "For Sale" is interesting as well. This might be a bit of humor, but in fact after the war there was an effort to sell the chasers rather then bring them back to the U.S.