The Boating Forum - Checking RPM's with photo tach
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Mad Guineau
11-21-2011, 01:20 PM
I am about to check the RPM's of my 6LP Yanmar with a photo tach to verify my gauge is accurate. Where should I place the reflective tape? I am assuming on the harmonic dampener?
Any help would be appreciated
Thanks
Esuomm1
11-21-2011, 01:21 PM
Yep, that's correct.
Mad Guineau
11-21-2011, 01:25 PM
Thanks
Main flywheel. My tach reads about 150 rpm's too high across the full range of rpm's.
Esuomm1
11-21-2011, 01:41 PM
You're welcome.
I had similar variances on my Yanmars too.
It's an informative exercise to perform (not trusting the tachs) especially, when surveying a new ride, to ensure propped correctly, engine performing well, etc.
Good luck,
J
offshorebri
11-21-2011, 02:15 PM
On my Yanmar 200HPs.....The port was 100 off and the starboard was 150 off. I was told almost all Yanmars are 100 off but my ears told me something wasn't quite right and the photo tach proved it. Sticker on the harmonic ballancer............
Mad Guineau
11-21-2011, 02:17 PM
According to Yanmar they actually say that their engines should run WOT under a load about 150-200 RPM's higher than what the manual says. My engine calls for 3800 max WOT and my gauge is saying 3750 so before I have my prop worked on I want to make sure the tach is accurate.
billinstuart
11-21-2011, 03:47 PM
Cheap and accurate method..shine a 120 volt fluorescent light on the flywheel..at 3600 rpms/1800 rpms (60 cycles per second) the flywheel will appear to stand still.