How'd they check RPM in the old days???

SV1000 · Mar 6, 2008

There has to be an alternative to this Tiny Tach gizmo. It's not so much the price but I "want it now". Is there any diagnostic tool that will check rpms on an outboard?

I used to have a dwell meter with a tach before I had my "modern" 77 Nova with an HEI distributer. Would this work?

wavrider · Mar 6, 2008

Re: How'd they check RPM in the old days???

Harbor freight has a tach that you point at the flywheel using reflective tape it will tell you rpms, Have to use it on the water, cover off engine, in gear at wide open throttle
HINT HINT tiny tach is safer

flabum · Mar 6, 2008

Re: How'd they check RPM in the old days???

Many multimeters have an inductive tach attachment. You can also use a frequency meter ( If you know how many poles the charging side of the staor is)

iwombat · Mar 6, 2008

Re: How'd they check RPM in the old days???

You can use your dwell meter off the pulse side of the coil. You can also get a timing light with an rpm gauge, or an inductive gauge w/ the timing light.

rolmops · Mar 6, 2008

Re: How'd they check RPM in the old days???

Very simple with RPM gauges.
On the old magnetic ignition engines (points) there was a wire connected to one of the points and another wire to ground.The gauge worked by "counting" the pulses and it showed them on an rpm gauge.

F_R · Mar 6, 2008

Re: How'd they check RPM in the old days???

How "old"? OMC dealers used to have a vibratach with reeds tuned to vibrate at a certain frequency. You just held against the motor and it counted the vibrations. Now that I've revealed my age, there are lots of shop tachs that use an inductive pickup clamped to a spark plug wire. Just make sure it is switchable to work on a two-stroke. That's all the TinyTach does.

SV1000 · Mar 6, 2008

Re: How'd they check RPM in the old days???

I live in a small city but I am looking for a timing light with rpm at the parts stores. I want to rent one for free as I did with the compression gauge.

I think the rpm gauge was a function of my dwell/tach unit that I used about 25 years ago. I must have chunked it once I bought my Nova in high school thinking it was obsolete...I guess it was except for boat motors!

flabum · Mar 6, 2008

Re: How'd they check RPM in the old days???

I have also seen tachs that look like a radar gun that uses sound to read RPm

R.Johnson · Mar 6, 2008

Re: How'd they check RPM in the old days???

FR: That reed type tach is made by Frahm, and still available. It's one of the most accurate known methods. They are far from cheap in price.

F_R · Mar 7, 2008

Re: How'd they check RPM in the old days???

Really? I had no idea they were still around. As I remember them, they also picked up all the harmonics. And you had to hold them just so or you got too much vibration pickup. Maybe accurate if you read them right, but the electronic ones sure are more user friendly.

reelfishin · Mar 7, 2008

Re: How'd they check RPM in the old days???

I use my Snap On timing light most of the time, it gives a digital readout through an inductive pickup on #1 plug wire. I also have a photo tach from Ford that works well on single cylinder motors, it works much the same as the Harbor Freight tach does. With mine you stick a small reflective tape on the flywheel and aim the photo eye at it to get a reading.

A vibratach can still be had from Brigg Stratton too, they are only really an option for single cylinder motors unless you are pretty experienced with them.

Most all digital timing lights now have a tach option that basically count ignition fire at one plug wire.

How'd they check RPM in the old days???

Petty Officer 3rd Class

Chief Petty Officer

Chief Petty Officer

Captain

Vice Admiral

Supreme Mariner

Petty Officer 3rd Class

Chief Petty Officer

Rear Admiral

Supreme Mariner

Captain