Recommendations for laser tachs?

[Geoff W.]

As the title says - anyone have recs for a remote tachometer I can use to verify my tach readings? Looking on Amazon they seem to range from $20-200 and I'm not sure what I'm looking at, to be honest.

 

[Christian Williams]

Good question. Do the $20 models actually work?

 

[Alan Gomes]

I use this one. Of course, I haven't checked this tach against a known standard. However, I checked it against a friend's optical tach and they agreed. Plus, the numbers it gives me seem believable, FWIW.

My Yanmar tach, by the way, is off, though not in a linear way. It is more accurate at the very low and high end, drifting off by as much as 250 rpm at worst. I made up a deviation table for it. But really, since I try to run the engine within a certain range of cruising rpms, those are the only numbers that interest me.

 

[Roger Janeway]

I have had very good experiences with the Neiko 20713A Digital Tachometer. I tested it on various things off the boat with a known RPM and it was accurate. It is very easy to use, and reports a minimum, maximum, and mean for the period of time that you point it at the rotating shiny thing and hold the button. My experienced local diesel mechanic was initially suspicious of the ~$20 Neiko until I used it to demonstrate that the tachometer his technician had been using to test my driveshaft RPMs was inaccurate.

Neiko 20713A Digital Tachometer, Non Contact Laser Photo | 2.5 - 99, 999 RPM Accuracy | Batteries Included (Renewed): Amazon.com: Industrial & Scientific

Neiko 20713A Digital Tachometer, Non Contact Laser Photo | 2.5 - 99, 999 RPM Accuracy | Batteries Included (Renewed): Amazon.com: Industrial & Scientific

www.amazon.com

 

[Christian Williams]

To check our engine RPMs, where do you put the reflective tape?

 

[1911tex]

I just borrowed this one from a neighboring boat at the marina. He showed me how it works...put a piece of shiny tape (included) on the flywheel (crank BELT pulley) and point the instrument at it once engine is running. He compared it to his Catalina boats' RPM gauge....which was off by 155 rpm at idle, 240rpm at 2000 rpm and 310 rpm at 3000 rpm. I have a different one on order (wish I had known he had one); however, these instruments work!

Akozon LCD Digital Tachometer DT-2234C+ Non Contact Digital LCD Laser Photo Tachometer Mini RPM Meter Tester: Amazon.com: Industrial & Scientific

Akozon LCD Digital Tachometer DT-2234C+ Non Contact Digital LCD Laser Photo Tachometer Mini RPM Meter Tester: Amazon.com: Industrial & Scientific

www.amazon.com

 

[Geoff W.]

My main takeaway is the $20 variety should do just fine. That's a relief! Thanks everyone for the input. It's funny how being a sailor has now made me suspicious of NOT spending a lot of money on a doodad or piece of equipment.

 

[Marlin Prowell]

And I have this one.

Amazon.com: uxcell RPM Tachometer Photo Non Contact Rotation Meter - 2.5 To 99999 Photoelectric DT-2234A : Industrial & Scientific

Amazon.com: uxcell RPM Tachometer Photo Non Contact Rotation Meter - 2.5 To 99999 Photoelectric DT-2234A : Industrial & Scientific

www.amazon.com

There are perhaps a dozen versions of this tachometer that are almost identical. They look like they are made by a single manufacturer and then relabeled.

I bought mine for a previous boat that did not have a tachometer so I could have some idea of engine RPM.

 

[ignacio]

I replaced the tach on my Yanmar 3GM30F a few weeks ago. The old OEM tach used a magnetic sender on the transmission bell housing. The new tach runs off the Balmar alternator I installed a few years ago. Not having a digital tachometer handy once I had everything installed, I was curious to see if there’s any apps that could help me at least get in the ballpark with calibration of the tach. To my surprise, there’s a few apps - some work using the phone’s light and camera, others use the microphone and an algorithm to analyze the engine sound patterns at idle. Out of curiosity, I tried the latter. It came in at 860 rpms, in the range specified by the manual. So I set the tach to that. Then increased to 2500 rpms. The app detected the change and matched to within 5-10 rpms. I’ll probably still get something more accurate later, but it’s good enough for now to get me out sailing.

 

[Alan Gomes]

I replaced the tach on my Yanmar 3GM30F a few weeks ago. The old OEM tach used a magnetic sender on the transmission bell housing. The new tach runs off the Balmar alternator I installed a few years ago. Not having a digital tachometer handy once I had everything installed, I was curious to see if there’s any apps that could help me at least get in the ballpark with calibration of the tach. To my surprise, there’s a few apps - some work using the phone’s light and camera, others use the microphone and an algorithm to analyze the engine sound patterns at idle. Out of curiosity, I tried the latter. It came in at 860 rpms, in the range specified by the manual. So I set the tach to that. Then increased to 2500 rpms. The app detected the change and matched to within 5-10 rpms. I’ll probably still get something more accurate later, but it’s good enough for now to get me out sailing.

Can you provide the name of the app? IPhone or Android? It sounds interesting.

 

[ignacio]

I used this one (iOS). But there were several that looked interesting.

 

[Bolo]

I have had very good experiences with the Neiko 20713A Digital Tachometer. I tested it on various things off the boat with a known RPM and it was accurate. It is very easy to use, and reports a minimum, maximum, and mean for the period of time that you point it at the rotating shiny thing and hold the button. My experienced local diesel mechanic was initially suspicious of the ~$20 Neiko until I used it to demonstrate that the tachometer his technician had been using to test my driveshaft RPMs was inaccurate.

Neiko 20713A Digital Tachometer, Non Contact Laser Photo | 2.5 - 99, 999 RPM Accuracy | Batteries Included (Renewed): Amazon.com: Industrial & Scientific

Neiko 20713A Digital Tachometer, Non Contact Laser Photo | 2.5 - 99, 999 RPM Accuracy | Batteries Included (Renewed): Amazon.com: Industrial & Scientific

www.amazon.com

At $22 and over 350 reviews with 4.5 stars on Amazon the Neiko 20713A Digital Tachometer seems like a good purchase. I’ve also been looking for an inexpensive hand held tach for my boat.

 

[Hagar2sail]

To check our engine RPMs, where do you put the reflective tape?

I also use the Neiko 20713A

Christian, I put mine on the lower drive pully, you can see it in this photo:

 

[eknebel]

You can always verify a optical tachometer. Point at a fluorescent light. The fluorescent light is blinking at Exactly 60 cycles per second in the USA. So you should read 60. This is a cal feature on lab grade ones I used to use.

 

[Hagar2sail]

IIRC that requires you to get the engine to 3600 RPM (not possible on most of our Diesel engines) or 1800 RPM would cause two stationary reflections to show up 180 degrees apart if used with the tape as shown in my picture right?

 

[gabriel]

https://tinytach.com/diesel-tinytach

 

[Sailingfun]

I use the Neiko on my Volvo MD7. Checked against a super professional tach reader... work very well!! You cannot beat the price...

 

[eknebel]

IIRC that requires you to get the engine to 3600 RPM (not possible on most of our Diesel engines) or 1800 RPM would cause two stationary reflections to show up 180 degrees apart if used with the tape as shown in my picture right?

I was too brief, sorry. The tachometers that I have used detected that the fluorescent light is the source of the strobing. It then reads in hertz, or 60. The tachometer’s usual internal light in normal operation (most are infra red) is reflected off the single piece of tape in normal operation. My cheap(ish) one reads 60 when pointed a a fluorescent light as well. If I could find it, I could tell you which model it is, but it is about 20 years old, and likely out of production anyway.
You are correct that if the tachometer doesn’t have this functionality, it should read 3600 aimed at a fluorescent light. 60 hertz x 60 seconds in a minute =3600 per minute. Away from North America, 50 hertz is more common; 50hertz x 60 seconds =3000 per minute. Sorry for the confusion

 

[Christian Williams]

Not saying I'll do anything you guys say, but my $20 laser tach arrived yesterday. It says I idle at 775 rpms, not 800, and 1500 rpms on the tach is really 1475. I guess I sorta knew that.

I think the real value will be WOT, to see how my 3-blade michigan sailor prop does against expected, and if I am getting all the rpms I'm owed. My GPS top speed is about 7.1 kn, which is where the stern buries anyhow. 2500 rpms on the tach is probably about right, but we'll see what the laser says.

...

The gizmo also measures how steady you can hold your hand when aiming the laser at the reflective tape of a stopped engine. My reading of 61 is the best I can do......

 

[Tom Metzger]

You can always verify a optical tachometer. Point at a fluorescent light. The fluorescent light is blinking at Exactly 60 cycles per second in the USA. So you should read 60. This is a cal feature on lab grade ones I used to use.

Oops... 120 flashes per second or 7200 per minute. 3 stationary marks at 2400 rpm.