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Tachometer Reading Too High RPM

K

kevinj

Advanced Contributor
I have the OEM Faria guages that came in my 2000 Crownline, 5.0L Mercruiser. Last year I noticed the tachometer was reading high and the problem persisted to this year. It's often showing about 1000RPM at idle and nearly 4500RPM at 30MPH. I can tell by the sound of the engine those tach readings are nowhere near close. Sometimes the idle shows correctly (about 600RPM) and others it shows 1000 or a little more. Again, the sound of the engine hasn't changed but the gauge has.

Any suggestions where to start? Does this sound like something in the ignition is putting out bad voltage or should I start on the tach end? I'm pretty certain I can handle the troubleshooting with my multimeter, I'm just looking for suggestions of where to start. If I know where to look I'm okay, but tracking down ignition and/or electrical system gremlins isn't my strong suit.

KJ
 
On the back of the tachometer there should be a selector switch, 4 cyl, 6 cyl 8 cyl.

Use a small flat screw driver and select a different setting and then re-select the correct one again (8 cyl)

Try that

Mine and many others do this from time to time and they kind of need a reset so to speak.
 
Ah yes, thanks for the reminder, I had forgotten about selector switches. I've had to rotate the pulse selector on 2-stroke engine tach years ago to fix odd behavior and didn't realize the 4-stroke tachs had similar switches. I'll give that a try and report back.

KJ
 
Thanks for the reminder. The dial on the old 2-stroke tachs just turned and I might have forgot to push in on this one.

KJ
 
I have twin Cummin 330s on my Skipjack 30. The tachs read 4000 rpm at 25 knotts. Cummins are supposed to top out around 2,800 rpm at 35 knots. So i have two issues. Boats too slow and tach arent ready correctly. Engines sound healthy id like to start by getting the tachs to read correctly. Any ideas?
 
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