differences in tachometer

[Richok]

I recently bought a teleflex tach for my boat. Someone ask me the difference between an auto tach and marine tach. I couldn't answer it. Does anyone know? Thanks in advance.

 

[CTD]

Re: differences in tachometer

functionaly the same, all the marine I have seen are plastic, auto are sometimes metal.

 

[gaugeguy]

Re: differences in tachometer

They both count ignition pulses. The auto tachs (and i/o tachs) count 3 pulses for a 6 cyl. engine, 4 for an 8 cyl engine. On ob tachs the pulses are counted from the stator, 3 pulses for a 6 pole stator, 4 for an 8 pole stator and 6 for a 12 pole.<br /><br />Diesel tachs are incompatable with gasoline auto and marine tachs because of where the tach signal is picked up from.

 

[Richok]

Re: differences in tachometer

Ok I guess I'm a little dumb on this but does that mean an auto tach won't work or will work with an ob? The guy that ask me has a 70 hp Evinrude. He wants to put a tach on his but don't want to spend what I did.

 

[gaugeguy]

Re: differences in tachometer

Couple options here...if the ob is a 2cyl it will not work (10 pole), but if it is a 3 cyl(12 pole)it would work if the auto tach is set up for a 6 cyl engine.

 

[Richok]

Re: differences in tachometer

Thanks gaugeguy, its a 3 cyl. I will pass this on to him.