Yanmars GM series do not use glow plugs. I fail to see the benefits for such a modification but it should not be to difficult. Look for a marine ignition switch with recoil, drill a larger hole in the panel and connect the wires securely to the correcponding terminals. Some of these switches come with the push to choke contacts but they can be left unused. My only concern is the protection of the recoil switch against the elements.