It will need a rectifier/regulator - not just a rectifier. I've done it for years with my 15 Merc/hatsu. I fitted an aftermarket unit though - made for motor bikes that can be run with or without a battery in circuit. You just need to confirm that the regulator is big enough to handle the current your stator can output and that at full noise the output is regulated to a suitable voltage as recommended by your battery manufacturer.