I have a 31 hp gatortail the motor is a vanguard does anyone know how many sparks per revolution i should set my tiny tach for

i set it to 360 degrees 1 spark per revolution but the readings are jumping from 1100 to 1700 at idle and from 3200 to 4800 at wot out of water what do you guys think

thanks....... i have tried wrapping the little red wire from 1 to 5 wraps on the plug wires on both cylinders with the same results i talked to the guys at the company that makes them and he is shipping me another one that he said is shielded to try he thinks it might be some kind of interference we will see in a couple of days

Mine did the same thing on a 23 hp Vangaurd i had to wrap it like 6-7 times worked great since.