How to tell if tach is right?

[ASTROCRAZY]

If I set the dial on the back of the tach to what my manual says it seems to high (idleing at 1600). That don't seem right to me. Do they make a rubber tipped manual gauge that I can hold against the flywheel? I need to get the tach right before I can start on set-up. Any help would be greatly appreiciated. Origial motor on boat was a Suzuki & now I have a Merc 2.4 EFI.

Thanks, Jeff

[ctered]

The tach may need to be changed. It may not be compatable with a Mercury if it was originally for a Suzuki. As for your question about a gauge with a rubber tip for checking rpm of an engine, the answer is "YES". I have a Stewart Warner gauge exactly like what you want. It has about a 3 inch extension coming out the back with a tapered rubber tip on it. You can measure the rpm of any rotating object with it.

Mark

[roadkill636]

you can also get one from a briggs and stratton small engine dealer, about $20

[apdcop7106]

Try a "tiny tach"

[ASTROCRAZY]

Thanks for the answers. Whats a tiny tach?

Jeff

[ctered]

A Tiny Tach is a brand of electronic tach that can be connected to about any motor. I had one on my quad. It has a wire that you curl around a spark plug wire to get a signal. Around $50 if I remember correctly. Can be moved from motor to motor though. Most small engine dealers carry them.

[150aintenuff]

make sure the suzuki tach has a 12 pole setting, that is what you need to make it work properly, sounds like its reading double the RPM.. (6Pole)

[Quinten]

Sorry to butt in, but I was looking for an idea to calibrate my tach. The tiny tach suggestion seems to be a great idea. I tried to look for this B&S small engine tach and all I found was a vibra-tach, is that it?

[T-REX]

Chech with ya local small engine repair shops...If they want to take the time to help U, they have several diffrent kinds ov test tachs at thier disposal...The best one I used when I wuz doin that wuz from Honda, and ya juss pointed it at the plug....It would only go to 6K, but would give a good ideer if Your tach iz in tha ballpark....We had to use them to set the rpm on the Honda generator sets we sold...

[marshan162]

How about one of these
http://cgi.ebay.com/New-DIGITAL-LASER-PHOTO-TACHOMETER-NON-CONTACT-TACH-RPM_W0QQitemZ110270183600QQihZ001QQcategoryZ1504QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I calibrated mine with a signal generator. from memory It needs 600Hz for 6000 RPM for V6 setting.
I'm guessing an unregulated battery charger off your 60Hz mains supply(should be 120Hz after rectifier) would show 1200 RPM. 'Not tested this'
On a mercury tach there is a calibration screw on the back, it makes a huge difference in the reading from min to max setting

[ASTROCRAZY]

Thanks you guys I'll let you know what I find. I will look tommorrow and see what the calibration knob settings on the back of my tach says.

Jeff

[Quinten]

Getting a couple of good test tools. Getting a tinytach 2RXL, as well as a hand tach I found on egay. It is a Stewart Warner like the one mentioned for 25 bucks including shipping. The tinytach will keep track of hours as well for gear oil changes and what not. Thanks Astro and others for letting me in on this. BTW, the tiny tach was $37.00

[benski]

There are a couple of places, at least, that carry hand held digital photo-electric tachs for about $80.00 These work very slickly, with just a small section of reflective tape applied to the spinning part, and instantaneous reading of RPM's. Hope this helps as an available option.

[Quinten]

There are a couple of places, at least, that carry hand held digital photo-electric tachs for about $80.00 These work very slickly, with just a small section of reflective tape applied to the spinning part, and instantaneous reading of RPM's. Hope this helps as an available option.

I saw those and wondered if it mattered where you put the tape. It seems the outer edge of the fly wheel would be spinning much faster than close to the middle.

[benski]

The outer edge of the flywheel is traveling much faster than at the crankshaft, but going exactly the same revolutions per minute.

[Quinten]

The outer edge of the flywheel is traveling much faster than at the crankshaft, but going exactly the same revolutions per minute.

Yeah, I guess that was a dumb question:o. A revolution is a revolution huh?:D

[benski]

There might be minor differences between French and Cuban, but in the world of physics, a revolution is indeed a revolution.

[C-Webb]

Traveling much faster but also a much longer way on a greater circle ;)

[Quinten]

I bought every bit of this:eek::o:leaving::smiletest:

[ASTROCRAZY]

I got one on the way. It should be here in a day or two. I post what I find out.

Jeff

[Quinten]

I just got a Stewart Warner mechanical contact. I like it. I got a tiny tach on the way. I'll post how both do as well.

[MarkHP]

Whe you got 1600 RPM at idle was this in the water or on the hose ? The idle will be much higher on the hose as the tuner gets 'loaded' when in the water.

[ASTROCRAZY]

That was on the hose.

Jeff

[MarkHP]

Put it in the water and then try it again.

[ASTROCRAZY]

Tested tach w/ a digital tach today. It was hard to hold it exactly on a given # but I did the best I could. Here is what I found:
Tach -- Digital tach
idle
1050 750-800 (jumps around alittle)
2600 2000
3600 3000
5400 4000

I will have to try & adjust the knob on the back of the tach to see if I can get it to read right. It had a Suzuki motor on the boat originally & now I have a 2.4 EFI Merc hi-perf motor. Should this tach be able to adjust to the Merc motor or will I have to get another one?

Thanks for all your guys help, Jeff

Jeff

[Quinten]

You can start by looking for a calibration screw on your tach, but it seems the error is rising exponentially. I don't know what kind of tach you have now, but it needs to have a setting of 12 pulse or 6 cylinder, sometimes denoted as 12p or 6c. If your tach is motor specific (not teleflex or gaffrig or some other) for Suzuki, you may need another one. Try to calibrate at idle and test again, if there are no other settings on the back, and it's still off, replacement is the answer.

[marshan162]

So you are aware, you have 2 controls on the back. One sets the number of poles/pulses and another inside a small hole 1/8" that you use for fine tuning, you should be able to bring it in with this. Its range will almost change the reading by a factor of 2. You'll need a fine screwdriver to get to it.

[Quinten]

Thanks Marshan, after reading ,my post, I did not successfully convey the fact that there should be two adjustment points on the back of the tach. One should be more like a dial with a pointer, and as Marshan said, the other will bwe recessed and have a very small slot in it. Good luck!

[ASTROCRAZY]

I will see if I can't get it dialed in by these two adjustments, You don't know how much I apprieciate you guys hooking me up on this problem. I have almost 7hrs on the motor and wanted to know how much I was pushing the ole girl. Next thing is to get the boat balanced out so it drives good when get ready to skin her back.LOL. I will keep you all posted on my progress.

Thanks again guys, Jeff

[pyro]

I used a Fluke digital multi-meter to test mine. It has a frequency counter function. I wrapped an insulated wire around a spark lead and grounded the other. Worked great!