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Author Topic:   tachy 3
SeaHag posted 06-10-2002 11:53 PM ET (US)   Profile for SeaHag   Send Email to SeaHag  
My tachometer will not go beyond 3000 rpm's, whats's up?? It works perfect at idle, trolling, etc., but when I'm running it stops at 3 even though its WOT. The motor is fine and runs like a champ, as recently inspected and tested.

Is there a 'switch' underneath the tach that can be adjusted?? Do I need to replace it?I'm at a loss. Help needed!

Thanks in advance.,

SeaHag posted 06-10-2002 11:55 PM ET (US)     Profile for SeaHag  Send Email to SeaHag     
ooops,,,, the referenced motor is a 1993 Evinrude 175 hp OceanPro.....
hauptjm posted 06-11-2002 09:37 AM ET (US)     Profile for hauptjm    
Possibly a bad sending unit? Have to admit though, they usually either work or not. I've never seen one work some of the time. Kind of like "sorta' of pregnant".
where2 posted 06-11-2002 12:44 PM ET (US)     Profile for where2  Send Email to where2     
Problem with charging system, or the tach. There is no sending unit, it relies on pulses from the flywheel magnets spinning around the coil under the flywheel. Coincidentally, this is the usually the same method that charges your battery. If it had totally stopped working, I'd think it was the rectifier diodes that turn the AC pulses to DC. Check operation with a known good tach, and diagnose from there.
jimh posted 06-11-2002 01:37 PM ET (US)     Profile for jimh  Send Email to jimh     
Possible explanations:

--the dial movement is mechanically stuck and cannot go beyond 3000;

--you have set the pulse count switch to the wrong setting and the calibration is off, making 3000 the reading for your WOT

simonmeridew posted 06-11-2002 07:28 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
Does the tach operate smoothly as you gradually increase the throttle and RPMs? Or does it stick at 3000rpm with more revs to go?
Support for the wrong pulse explanation JimH gave is that while it may look like your idle indication is "perfect", if for example you are 3000rpm/6000rpm or half the number of pulses off, a tach that reads say 400rpm at idle when it should read 800rpm would not look much different, that is, it is difficult to discern the difference of a few hundred RPMs but 50% of WOT would be very apparent: 3000rpm vs. 6000rpm.
Like the bumper sticker says, "Assume nothing"
I'd vote for the wrong pulse count.
SeaHag posted 06-11-2002 09:56 PM ET (US)     Profile for SeaHag  Send Email to SeaHag     
So Jim and Simon help me here. I'm leaning more to the pulse count also, as the rectifier has been replaced 3 weeks ago. {I still had the problem before hand so it wasn't anything the mechanic did.)

That being said how do I change the "Pulse Count" on the tach? Is there a switch located somewhere that I can change?

Your help is much appreciated!!!!!!!

Tom W Clark posted 06-11-2002 10:01 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

The pulse count is adjusted by rotating a little dial on the back of the gauge with a screw driver. There is an index around this dial which will indicate how many pulses it is set to.

My money is on the gauge's needle simply being pegged at the 3000 mark by some debris in the gauge itself behind the dial.

jimh posted 06-11-2002 10:02 PM ET (US)     Profile for jimh  Send Email to jimh     
On most of the "universal" Tachometers there is a multi-position rotary switch, although a small one, located on the rear panel of the gauge.

If you have an OEM tach there may not be a calibration switch since the maker of the gauge already knew the application it was intended for.

SeaHag posted 06-11-2002 10:07 PM ET (US)     Profile for SeaHag  Send Email to SeaHag     
okay,,,, I'm pleading ignorance but what should the pulse count be set at??


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