Erratic Tachometer Yamaha F150

[dckhntr]

I have had some troubles with batteries in my F150 recently and even a blown fuse or two.

Yesterday I was running with only my F150 connected to the battery (no accessories) and noticed after 45 minutes or so the analog tachometer starting varying by more than 3000 rpm even though the engine did not change rpm.

Many years ago this happened to my Evinrude 2 stroke and it was the rectifier. I've also seen some odd voltages (like 16V on both my depth finder and analog in-dash volt meter).

Has anyone encountered a failed rectifier/regulator on a Yamaha 4-stroke? Would you expect the rpm to vary widely if the rectifier/regulator was out?

 

[gm280]

:welcom: aboard dckhntr to iboats...

Usually tachs are connected to the stator side of a rectifier/regular module. And if the rectifier had some diodes bad, then it would make the tach act up with all types of issues. So it could be a bad rectifier indeed. I can't say that for certin not being there and testing things, but it does point to that. However, I would also check all the connection between the rectifier and even on the tach itself to verify all connections were clean and tight. JMHO

 

[99yam40]

need to find out where you signal is coming from as some of the larger motors have the tach signal generated by the ECU

Did you happen to hook up the battery backwards causing the fuses to blow?
may have hurt other things

 

[dckhntr]

I appreciate the replies. I had some connection issues on the ground and in the process of troubleshooting I left the battery terminals loose. I didn't hook it up backwards but lost connections while running. I had heard that losing the positive connection while running could damage the rectifier.

I'll look into the ECU, that's a good point.

The negative connection on the block looked pretty bad (maybe even arced) so maybe that caused some feedback through the system? I've really gone through the tach connections so I feel pretty good about those connections.

If the tach runs off of the stator I'm tempted to just buy a new rectifier/regulator and give it a try.