A better method is get the prop spinning
Incident: Instructor and student practicing gliding turns. During straight glide and approaching 1000 feet above the coast the propeller gradually slowed down over a 15 second period and stopped. Instructor transmitted Mayday and turned to ditch along side boat that was 50 yards off shore. Student petrified so instructor reached across student and attempted restart re starter key with no luck. Instructor again reached over and gave one pump at primer then tried a restart. Immediate start accomplished at 500 feet. By sheer chance the same instructor had a few weeks earlier endorsed the maintenance release for a jamming primer plunger which was rectified by an LAME
Interestingly, same aircraft with different instructor had stopped prop during lead up to practice stall recovery. Instructor dived aircraft to get prop turning and after considerable height loss was successful. Instructor should have endorsed the defect in maintenance release but elected not to do. The reason for the prop stopping lay undetected until the next time the aircraft flew and came to close to ditching.