Bench testing a Tachometer? Are Tachometers motor specific or are they generic fit?

[Bubbasboat]

Is there any way to bench test a tachometer?

Are tachometers model specific, or can any tachometer work on any motor?

 

[Barnacle_Bill]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

They can be bench tested if you have the special equipment to do it. They work off an AC pulse from the charge coils usually part of the stator.

 

[airshot]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

They work off the electrical signal from the engine, a tach must be wired according to the number of cylinders it has. The only way I am familiar with testing a tach is to find someone with a portable tach to make a comparison. I have a friend that works on autos and has a portable tach that we used and the company I work for has a mechanical hand held tack, we used all 3 of them together and found each was within 50 rpm of the others so I feel comfortable my tach is good.

 

[Bubbasboat]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Based on your answer, the fact that I removed a 4 cylinder 115 hp motor and replaced it with a 3 cylinder 70 hp motor, I probably need to replace the tach, or can it be rewired to work with the 70hp? I have been told my remote controls and electrical harness are compatible.

They work off the electrical signal from the engine, a tach must be wired according to the number of cylinders it has. The only way I am familiar with testing a tach is to find someone with a portable tach to make a comparison. I have a friend that works on autos and has a portable tach that we used and the company I work for has a mechanical hand held tack, we used all 3 of them together and found each was within 50 rpm of the others so I feel comfortable my tach is good.

 

[NYBo]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Based on your answer, the fact that I removed a 4 cylinder 115 hp motor and replaced it with a 3 cylinder 70 hp motor, I probably need to replace the tach, or can it be rewired to work with the 70hp? I have been told my remote controls and electrical harness are compatible.

Outboard tachometers usually read the pulses from the stator, and most of these are 12 pulses per revolution. No rewiring needed, and most likely, no need to even change the setting on the back.

 

[Bubbasboat]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Thank you for this info.

Outboard tachometers usually read the pulses from the stator, and most of these are 12 pulses per revolution. No rewiring needed, and most likely, no need to even change the setting on the back.

 

[airshot]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Us old sea dogs learn something new everyday, in my day the tach had to be rewired or a switch changed according to the number of cylinders the engine had and whether it was 2 stroke or 4 stroke.......You young guys really have things easy..LOL

 

[NYBo]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Us old sea dogs learn something new everyday, in my day the tach had to be rewired or a switch changed according to the number of cylinders the engine had and whether it was 2 stroke or 4 stroke.......You young guys really have things easy..LOL

Who you callin' young?

 

[saumon]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

Us old sea dogs learn something new everyday, in my day the tach had to be rewired or a switch changed according to the number of cylinders the engine had and whether it was 2 stroke or 4 stroke.......You young guys really have things easy..LOL

You're right but as NYBo said, most work on the 12p setting, even if there's a lot of exceptions. Better check with your tach manufacturer for your particular engine. Here's the Faria chart as an example (scroll down to the last page):

http://faria-instruments.com/site_manuals/IS0012u.pdf

 

[gm280]

Re: Bench testing a Tachometer? Are Tachometers motor specific or are they generic f

I actually built a tach in my days. It was a Heathkit and it worked very nicely too. And their method of calibration was to use a little circuit that plugged into a standard AC outlet to allow the tach to read the 60hz pulses and verify the tach reading and adjustments. If you have a function generator you can test any tach. But most use a portable tach and verify their tach with the portable tach. I also have two "Tiny Tachs" that will read on most any ignition type engine. And they can verify you have your tach set properly... SO yes there are ways. JMHO!