Tachometer Pulse's

[MokiCruiser]

So I already posted below but I'm not getting any responses so I'll pose this question another way, maybe someone else will see it. I am not too savvy when it comes to electronics but I can usually muddle my way through anything if I get a little advice, so then here's my question another way. According to some posted questions I've read her at I-boats about 1975 Johnson 70 hp motors, I've learned that this 3 cylinder model Johnson needs a 6 pulse tachometer. So my question is, is a pulse a pulse? As you know, anything designed for an outboard can be expensive, but for some reason used snowmobile tachs are relatively cheap. So if the snowmobile tach says that it is 6 pulse (printed right on the back), is there any reason that it would not work with my Johnson. I'll add pictures from one I can buy at Ebay for very cheap (and there's quite a few). Thanks and would really like some help from anyone that might know.

Also if it would work, would the wiring be red = positive 12 V, and black - ground, and yellow the signal (brown on the Johnson)?

 

[Bosunsmate]

Pulse is a pulse from the ac on the rectifier, id go for it myself.
Black ground so brown is the signal although on mine its grey

 

[MokiCruiser]

You're absolutely right Bosun about the color, gray on mine too, not sure what I was thinking ........... and thanks for the input on "pulse", I'll buy that tach then!

 

[interalian]

The only negative I can see is the tach is 10,000 rpm and you can only use half of it. But I like the 'cheap as chips' idea. Hope it works out for you.

 

[Bosunsmate]

Yes good luck and report back if possible

 

[MokiCruiser]

After I paid for the tach yesterday at Ebay, I looked up the snowmobile that the seller said it came from, and as it turned out it was powered by a 3 cylinder 2 stroke engine which is the same configuration as my 1975 70 hp Johnson. And as interalian mentioned (above) about the 10,000 RPM on the Polaris tach, I took another look at the motor specific Johnson tachs and they are all 7,000 RPM gauges ................ so I have an extra 3,000 RPM, I can live with that if it works cause it was a ton cheaper than the price of a new OEM Johnson gauge.

After I get the tach and get it installed I'll get back and update this post, if it works, maybe some other folks that have an older or even newer Johnson in need of a tach but don't want to shell out $100 to $200, might do the same. Right now on Ebay there are dozens of these 6 pulse snowmobile tachs listed under $30 VS. $80 to $250 for a Johnson specific tachometers. Thanks again!