Tachometer jinking around

[metalwrkr]

I have a 2005 Honda 90 in real nice shape.  Yesterday starting out I noticed my tach RPMs jinking around up and down even though the revs were steady at cruising speed.  The needle would jump from 4400 to 5000 to 3800 to 5400 all over the place.  it would settle down and star jumping again.  After a short time it settled down and worked fine.  The culprits are obviously; gage, wiring or sending unit where ever that is.  I will start by cleaning all contacts and spraying moisture displacement on them but where to go from there?  Anybody had this problem?  How would you troubleshoot this?  Thanks.......Russ K. 

[Hydroman]

On many tachs there is a selector switch (may be under a small plug) to match the tachs to a specific engine. 

Just rotate the switch several time and it may wipe the contacts clean. Make sure you check the as found position so you make sure it get left in that position.

Jim

[Threeweight]

If it worked fine previously, his tach is likely already matched to his engine.

I would suspect either a bad ground, or bad wiring.

[Diablo]

Tack signal comes from the alternator. Check your connections there and at the tack for tightness or corrosion, clean and tighten. You could also be having indications of a part that is failing. Good luck.

[Hydroman]

Threeweights,

I realize that the tach worked previously.  However it is no uncommon for the contacts in the selector switch to develop a poor contact over time from moisture and just be subject of bouncing around.

Jim

[Chief of the Boat]

Do you have the standard analog Honda tach with an hour meter?   I agree with Jim on the contacts on the selector switch corrosion under the cowling.
:twocents: 

[DevMah]

All the info so far sending you in the right direction....


The black wire on your tach is B- the black yellow switched 12v B+ and the gray goes to the regulator/rectifier.

Check you connections at the gauge and the connector at the engine.
It is possible that you may have loose/bad connections, broken signal wire a failing tach or rectifer.

Dev

[rasslingref]

My 1999 Honda 90 does the same thing. I have a corroded connection at the gauge but I'm too lazy to fix it. It's the ground  wire that gets corroded and I finally found the source for the water coming into that area. Horn cover leaking.   Hehe
OK so I did fix it but I'm still lazy.


Sent from my iPhone using Tapatalk

[metalwrkr]

Was finally able to get in touch with my "ACE" Honda tech late Friday.  He said this is a common intermittent problem with the causes from most to least probable being: moisture on contacts, corrosion on contacts, bad corroded or incorrect wiring and last, failure on the sending side (engine).  Solution: clean all contacts both at the gage (this includes rotating the tach selector switch) and engine (there is a junction box at the engine) and any junctions or fuses in line.  Spray these connections with moisture displacer/ corrosion block.  Run the boat and hopefully the problem is solved.  If not, beg borrow or creatively acquire a temp tach that works and hook it up and run the boat. If it works correctly then your original tach is bad (don't forget to return the borrowed tach). This procedure will solve 90% of the problems and is fairly owner friendly to do.  If there is still a problem and you are not a more advanced trouble shooter, his suggestion is to bring the boat in for service.  All his info seems to jibe with forum input.  I have now done all the cleaning and spraying but have not had a chance to retest.  I guess another fishing trip is in order.  Thanks for all the input and Rasslingref you really should jump on that fix!.....RK

[Foxsea]

Mercury outboard I had with that issue, found out had a bad voltage regulator. Another option to check.

[milos dad]

The Honda tach on the Arima I bought had the needle jumping around when doing the river trial.  Dealer replaced the tach and it has worked fine since.

M D