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Question

I have a 1998 150hp Merc 2-stroke outboard and my tach has just all of a sudden started running high (~1000 rpms off at the low end and 2000 rpms off when I am running at 3/4 to WOT). I am confident my motor isn't running at 2000 at min wake and at 6500 - 7000 (!!!) when I am crusing at planing speed. Wondering why Tach calibration could have been thrown off. Only thing I can think of is that I recently had a dead battery (assumed it was bilge pump and rainy June here) and had to disconnect, recharge battery to full and then reconnect. Did some looking on line and am afraid dead battery and tach may be a faulty voltage regulator. Or maybe I crossed some wires when I reconnected battery? I am not electrical savvy but if there are some simple troubleshoots I could do I would appreciate.

Submitted: 257 days and 21 hours ago.
Category: Boat
Value: $15
Status: CLOSED

Accepted Answer

Hello Fishy,

The tach gets its signal from the voltage regulator (the 2 boxes behind the coils). Both have gray wires but only one regulator is connected for the tach (gray wire) . You can swap the wire to the other regulator and see if the tach settles down. If it still acts up it is most likely a bad tach.

 

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Expert: Mechman45
Pos. Feedback: 97.2 %
Accepts: 254
Answered: 7/6/2009

Marine Mechanic

30 Year Service Tech Gas/Diesel.

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