Reply
 
Thread Tools Search this Thread Display Modes
 
Old 08-09-2018, 02:52 AM   #1
Lt. JG
 
Join Date: Jul 2016
Posts: 17
Default Tachometer Calibration

I have a 2800 SCR with a 7.4 and Bravo 3 out drive and a 22 pitch props.

My tach is reading 5900 rpm WOT at 36 mph. Doing the calculations for the pitch of the prop and the gearing of the outdrive, the speed is correct, but the RPMs are reading about 1100 rpms too high.

Is there a way to calibrate the tach?
__________________

Jduncan99217 is offline   Reply With Quote
Old 08-09-2018, 03:13 AM   #2
rwc
Lieutenant
 
Join Date: Sep 2017
Location: Vancouver, Canada
Posts: 66
Default

Speed is not a good measure as resistance curve becomes exponential past plane. Speed won’t change that much with RPM, but engine load and fuel consumption will.

You might just need a higher pitch on your propeller.

Your propeller would be designed to cavitate 5 to 8% at full power, design RPM (4800), so at 5900 you would also be cavitating heavily, which could also cause you not to increase speed.
__________________

rwc is offline   Reply With Quote
Old 08-09-2018, 08:29 AM   #3
Admiral
 
mmwjr's Avatar
 
Join Date: Feb 2012
Location: Essex, Maryland
Posts: 6,555
Default

Get a photo tach from an auto supply store to measure the rpms. Calibration is factory set and cannot be adjusted.
__________________
Mike
mmwjr is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT. The time now is 03:33 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2018, vBulletin Solutions, Inc.