"The Dappled Thing"

by William Browning Spencer
Originally published Subterranean: Tales of Dark Fantasy, 2011

In some odd, steampunkish England, Lord Addison has built a bizarre vehicle called Her Glory of Empire. which comes armed with mechanical tentacles and other goodies, and hires Sir Bertram Rudge and a crew to pilot her into South America in search of his granddaughter, Lavinia, who has run off with a party led by a man named Wallister.

There they find a strange tribe called the Yami, and monster (a shoggoth?) living in a lake.  The monster tries to take Lavinia and Wallister, but Her Glory of Empire is used to attack it.  Lavinia and Wallister are rescued, but the monster takes over Her Glory of Empire and stomps into the jungle.

Certainly one of the odder Lovecraties I've read.  Not bad at all but hardly a classic.