Hour Meter Question - Tiny Tach Etc

[HAZ]

Hi,
Can anyone tell me if you can use a Tiny Tach or Sendec Hour/Tach Meter on a 4 Stroke 25hp Yamaha ? I have searched and found different answers but no final verdict. I have even contacted the agents for Sendec and this is the reply I got - 'The rpm might not display correctly, but the hourmeter should work fine. You need one spark per revolution to get the rpm to work correctly. Can anyone tell me if the motor is one spark per revolution ? or I also have read that the wires that wrap around the spark plug lead may have to wrap around both to read the revs correctly. Can anyone shed any light on the matter ?
Thanks
HAZ.

[Noelm]

not too sure about your exact motor, but the general theory of 4 stroke operation is 1 spark for 2 revolutions of the motor, however some still spark, even on the non power stroke, so without some very in depth info on your motor, I would be thinking probably no, not 1 spark per revolution.

[captain rednut]

Hi,
Can anyone tell me if you can use a Tiny Tach or Sendec Hour/Tach Meter on a 4 Stroke 25hp Yamaha ? I have searched and found different answers but no final verdict. I have even contacted the agents for Sendec and this is the reply I got - 'The rpm might not display correctly, but the hourmeter should work fine. You need one spark per revolution to get the rpm to work correctly. Can anyone tell me if the motor is one spark per revolution ? or I also have read that the wires that wrap around the spark plug lead may have to wrap around both to read the revs correctly. Can anyone shed any light on the matter ?
Thanks
HAZ.i have one on my 2stroke 3 cyl yammy and its perfect.