Need help with tach problem Yamaha 115 Four

[altondrive]

I installed a new tach but didn't have the pole set correctly. I reset the pole and the tach would come up to about 500 rpm on start of the motor then back to 0. I bought a second tach and installed it with the pole set correctly. Started the motor and got the same thing. If I unplug the green wire going to the tach and touch it back to connect I get the same jump on the tach but again, back to 0. The ground is solid, the ignition wire is solid, the tach signal wire is solid at the tach. The amp meter registers the motor is charging. Where else to look for the problem? Obviously the first tach is good too so now I have invested in two tachs and neither work. Explain that to the wife!

Both tachs are analog.

Thanks in advance for any help you can provide!

 

[robert graham]

Re: Need help with tach problem Yamaha 115 Four

I had a similar problem and it turned out to be a very slight bit of corrosion in the in-line fuse to the tach. I cleaned contacts, a bit of WD-40 to help keep out moisture and it was good to go. no way you've got 2 bad tachs..has to be in the wiring. Good Luck!

 

[altondrive]

Re: Need help with tach problem Yamaha 115 Four

Bump

 

[stylesabu]

Re: Need help with tach problem Yamaha 115 Four

I did similar thing with my suzuki, i bought 3 used tachs.none of them worked. I found that my engine wasn't charging, fuse blown once i replaced fuse my tachs started working. you are looking for over 12.9 volts or higher 12.6 is battery voltage, you should probably see about 13- 14 volts

 

[altondrive]

Re: Need help with tach problem Yamaha 115 Four

I believe I have good charging level but the blown fuse makes sense to me. When I took the first tach out to reset the pole setting I set it back without re-installing it and started the motor. When I turned of the motor and picked the tach up to see what the problem could be I found the bracket had fallen and rested on the send and ignition poles of the tach. That's why I thought I blew the tach but maybe a fuse somewhere. Now to find it. Thanks for both your help! I do appreciate it! Now off to find where that fuse could be.

 

[altondrive]

Re: Need help with tach problem Yamaha 115 Four

I checked all four fuses under the motor cowl and all are good. I put my test light grounded to the ground on the tach. Turned on the ignition and got power to the ignition side of othe tach then started the motor and got power to the send side of the tach but still no tach. I jumps to about 1,000 RPM then bach to 0 each time I start the motor. I'm lost to where to go from here. Any help, Please!

I'll even offer a free set of boat numbers cut out of premium vinyl of your color choice to anyone that guides me in the right direction.

Thanks again for everyone's help!

 

[rodbolt]

Re: Need help with tach problem Yamaha 115 Four

start with a known good ground, the ign terminal on the tach should show 12V. then check from the ign terminal on the tach to the ground terminal,should have 12V. this will check if you have a tach ground problem or a 12 positive supply problem.
the tach send terminal can be checked using the AC meter function and a known good ground.
dark green is tach send,yellow is key on 12V and black is ground if the wireing harness is still yamaha.
tach send is generated by the ECU.