Tach problem - need help

[Kim Becker]

Yesterday while running WOT I noticed my rpm's at 6000. I always check my guages while running so I know this just happened. I have a 1998 Mercury 125 HP normally taching 5200 - 5400. I came off plane and started back up and all was fine. Several times during the day it happened again. My question is, would I not have heard a change in the motor if it was indeed at 6000 rpm's. Would I not have noticed a change in performance at 6000 rpm's. If a tach goes bad do they surge like this ? I am ruling out prop issues as it will read high in nuetral sometimes. I am thinking bad tach, bad sensor, bad voltage regulator, motor problem. Anything else I should be looking at ? Thanks in advance. I know someone on here will have an answer for me. You guys are the best source of information anywhere.

 

[G8rmac]

You would almost certainly hear a difference between 5400 and 6000. It's not unusual for a tach to start acting weird, I can tap on mine when it does this and it will settle down. You can start by checking the connections to make sure they are clean and tight, but anything more than that is beyond my expertise. Search the older posts, I know this was a topic a couple of months ago.