Tachometers - will automotive tachs work or strictly marine?

[CaneCutter79]

Can I use a lesser inexpensive automotive tachometer for a smaller outboard? I found one that will work on 4, 6, and 8 cylinder engines.

I'm guessing this is a stupid question and only a marine tachometer will work correct?

I have an 85hp Evinrude V4.

 

[basspirate]

Re: Tachometers - will automotive tachs work or strictly marine?

you could use a automotive tach set to 4 cylinders if you have a four cylinder but you will have to divide the reading in half because an auto tach fires twice as much and at wot you wont get an accurate reading unless your tach goes to 13000 rpms

 

[imnezrider]

Re: Tachometers - will automotive tachs work or strictly marine?

Take a look and read up on this...may work for you.

http://www.tinytach.com/tinytach/gasoline.php

 

[Chris1956]

Re: Tachometers - will automotive tachs work or strictly marine?

Cane, if your OB has a distributor, the CD ignition is not too different from an auto and you can get to the - side of the ign coil, it may work on the 8 cylinder setting.

 

[Silvertip]

Re: Tachometers - will automotive tachs work or strictly marine?

Automotive tachs work off the ignition system and are "cylinder based". Outboard tachs could care less how many cylinders the engine has since these tachs operate by counting the pulses from the stator (charging system). If the auto tach will recognize the very different pulse shape then you can do the math to equate the number of cylinders on an auto engine to 6 pulses per rev from most outboard stator systems. If the auto tach doesn't recognize the wave shape then this is all a moot point.

 

[F_R]

Re: Tachometers - will automotive tachs work or strictly marine?

Automotive tachs work off the ignition system and are "cylinder based". Outboard tachs could care less how many cylinders the engine has since these tachs operate by counting the pulses from the stator (charging system). If the auto tach will recognize the very different pulse shape then you can do the math to equate the number of cylinders on an auto engine to 6 pulses per rev from most outboard stator systems. If the auto tach doesn't recognize the wave shape then this is all a moot point.

Nearly all outboards made in the last 40 years use alternator (stator) driven tachs. The tach counts the A.C. pulses from the alternator. Car tachs counting primary ignition pulses won't work on them. Period. Inductive tachs like the Tiny Tach will work because they count the sparks on a plug wire.

The exception would be if it is old enough to have a 12V points and condenser type distributor...like an old car.