Duesenberg Straight-8 "Walking Beam" marine engine (1916). 
B x S was 6.75 x 7.75 in., Output 410 HP at 1500 RPM. Built by the  Loew-Victor Engine Company in Chicago, Ill.
Unknown author<span style="display: none;">Unknown author</span>
CC BY-SA 4.0
Motor Boating, September 1916; <a rel="nofollow" class="external free" href="http://theoldmotor.com/?p=25565">http://theoldmotor.com/?p=25565</a>