Tach Problems

P

prater

Seaman Apprentice
Joined
Apr 14, 2009
Messages
49
Lately my tachometer has been jumping straight to 6,000 RPMs any time the engine is running. Its not stuck because it goes back to 0 when the engine is shut off. What could cause this?
 
R

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: Tach Problems

The first thing I'd check is the little pole setting screw on the back, just move the setting back and forth with the motor running and watch your needle, maybe that's it, then double-check your wire connections on the back, they are very sensitive to a bit of corrosion on the connections or looseness. You could turn your motor on and jiggle those wires and look for a reaction from your tach needle. One other thing to check is your fuses, especially those in-line jobs that can get loose or corroded. Good Luck!
 
T

TwoFish

Petty Officer 1st Class
Joined
Aug 7, 2010
Messages
373
Re: Tach Problems

Had a similar problem and fixed it a couple of weeks ago. Mine was reading hight by anthing up to 1500 revs. I have a 1998 - 75hp Force. I?m only new to working on outboards so I?m no expert. I read some where that interference on the signal wire can cause the tacho to run high.

It as only a corroded connection on the grey signal wire from the regulator. Mine was in the main wiring connector at the back of the motor. Used the ohms setting on a multi meter and found some resistance in the wire. Traced it back to the connector. Cleaned it up and the tacho now works.

If you have an earlier model outboard it may have a rectifier and not a regulator. The signal wire as I understand it is taken from one of the stator wires in this case. You will need to look this up in your manual.

The regulator on mine has 4 wires. I?ll look up the colors when I?m near the manual. From left to right from memory.

Two yellow that come from the stator( ac current).

One grey signal wire to the tacho. This is essentially only one of the stator wires that has a filter on it. If the filter is broken it is still possible for the regulator to charge correctly but not send a good signal to the tacho. I haven?t tried it but I understand it is possible to get a signal to the tacho from one of the stator wires.

One red wire. Positive wire to the engine (DC current)

The regulator on mine grounds itself to the engine through the body of the regulator. Some regulators have a black ground wire. Check to see if the regulator has a good ground.

I was planning to run a new wire from the grey wire on the regulator to the back of the tacho if I could not find a bad connection. This would be another way to help diagnose the problem.

Good Luck
 
You must log in or register to reply here.
Top