Electromagnetic actuator for heat engine starter, comprising: - at least one coil (24; 25) for creating a magnetic field when it is electrically powered; and - a magnetic circuit for circulating through the latter a magnetic flux generated by the magnetic field created by the coil, which magnetic circuit comprises: o a yoke; and o a mobile core (121; 221; 321) that is mobile from an initial position to a final position; in which: - the magnetic field of the coil creates a magnetic force acting on the mobile core to displace it from the initial position to the final position, and - the yoke and the mobile core each have at least one protuberance (Sc, Snm; Sc1, Snm1; Sc2; Snm2), the protuberance of the yoke forming an opening, and in which: - the protuberance of the mobile core in initial position is outside of the opening, - the protuberance of the mobile core penetrates into the opening when the mobile core is displaced from the initial position to the final position, and - the protuberance of the mobile core remains in position of penetration into the opening when the mobile core is in final position, in which the yoke has a first opening, the mobile core being displaced from the initial position to the final position by dipping into the yoke through the first opening; characterized in that - the yoke has a second opening, the mobile core being displaced from the initial position to the final position by dipping into the yoke through the first opening towards the second opening; and - the mobile core has a frontal part forming one said protuberance of the mobile core, in which - the frontal part of the mobile core in initial position is outside of the second opening, - the frontal part of the mobile core penetrates into the second opening when the mobile core is displaced from the initial position to the final position, and - the frontal part of the mobile core remains in position of penetration into the second opening when the mobile core is in final position. - at least one coil (24; 25) for creating a magnetic field when it is electrically powered; and - a magnetic circuit for circulating through the latter a magnetic flux generated by the magnetic field created by the coil, which magnetic circuit comprises: o a yoke; and o a mobile core (121; 221; 321) that is mobile from an initial position to a final position; o a yoke; and o a mobile core (121; 221; 321) that is mobile from an initial position to a final position; - the magnetic field of the coil creates a magnetic force acting on the mobile core to displace it from the initial position to the final position, and - the yoke and the mobile core each have at least one protuberance (Sc, Snm; Sc1, Snm1; Sc2; Snm2), the protuberance of the yoke forming an opening, - the protuberance of the mobile core in initial position is outside of the opening, - the protuberance of the mobile core penetrates into the opening when the mobile core is displaced from the initial position to the final position, and - the protuberance of the mobile core remains in position of penetration into the opening when the mobile core is in final position, - the yoke has a second opening, the mobile core being displaced from the initial position to the final position by dipping into the yoke through the first opening towards the second opening; and - the mobile core has a frontal part forming one said protuberance of the mobile core, - the frontal part of the mobile core in initial position is outside of the second opening, - the frontal part of the mobile core penetrates into the second opening when the mobile core is displaced from the initial position to the final position, and - the frontal part of the mobile core remains in position of penetration into the second opening when the mobile core is in final position.