Tachometer Help Please

[Punch953]

Guys, I replaced my old 1992 Yamaha 200 with a somewhat newer HPDI 200. I used adapter harnesses from Yamaha and everything except the tachometer seems to be working. The tach is just blank-nothing. Any ideas? Thanks

[99yam40]

just what model # is this 200HPDI and what tach

Make sure it is getting 12 V to it
or are you saying it powers up and shows other stuff on the screen, but have no RPM read out?

most old motors used a pulse from the lighting coil for tach some newer motors have a signal from ECU

[fairdeal]

when you say 'blank' -
do you mean you have a 'multifunction' tach with LCD digital display ?
that has the rpm, trim position, and oil indicators?

and you see 'nothing' ?
or the display 'works' - but you just don't have anything in the rpm field?

[Punch953]

Sorry I took so long. For some reason I couldn't log back in. The boat is a 1992 Grady Seafarer. It had the original 200TXRQ. I replaced the engine with a 1991 VZ200. The tachometer is the original one from 1992. This is not a pic of my actual tachometer but it looks like the starboard one in the picture. The tach lights up but that's about it. The readout is blank. A local Yamaha-not authorized-told me that he has seen this before with swaps and it required adding a wire from the key switch or the shifter-he can't remember-to the tach. Not much help I know.

[99yam40]

are you sure about this?
"I replaced the engine with a 1991 VZ200"

does it have a model and manufacture date on the motor tags?
you said it was a newer motor than your 1992 in your original post

Saying the tach lights up , maybe it is the light bulb inside, but the electronics are not getting 12 v power
could it be that the key switch is tied to the light and not the main power into tach

[Punch953]

I meant 2001. I'm going to have to check for power but I have a feeling that it is a wiring or incompatibility issue as the gauge worked fine until I swapped out motors.

[fairdeal]

I'm still not understanding.
The tachometer does not just display the rpm value;
separately, it displays trim position,
separately, is has indicator lamps.
Those are all wired separately -
although they all need the same basic power and ground.

That is the yellow wire and black wire from the key switch -
and it makes no difference what engine model is at the back.

When you first turn the key - does the face of the display do a 2-3 second self-test?
do all the LCD segments go on - visibly black ?

[Punch953]

Fairdeal, it does nothing. Worked fine on the old engine so I assumed there was an issue in the back of the boat. I may have been overcomplicating this and over the weekend I will check the basics. I'd like to thank you all and I will report back.

[fairdeal]

of the wires coming out of the back of the tach -
some go to the engine, for the warning indicator and trim:
those are the two multi-wire plugs.

Then there are individual wires with 'bullet' connectors,
these should all plug in a harnes that goes to the keyswitch/remote control:

green is the tach signal - if you don't have that, the gauge will still 'work' -
you'll just get "--" for rpm

yellow is power
black is ground
you have to have both, for the gauge to display anything

now, there is an inline fuse in the harness from the keyswitch -
a black 'pod' that separates into two pieces -
perhaps that is your problem.

[Punch953]

Fixed! Thank you fairdeal and everyone else. For some reason the tach ground went to the engine-to a bullet connector that was no longer used. All I had to do was un-plug the black wire from the back of the tach and plug it in to the harness going to the speedo/fuel gauge and it works fine! I guess I got tunnel vision as it worked before the engine swap. Thanks all again.

[99yam40]

without a ground I do not see how it could have lit up or even a light bulb in it light up when you turned on the key, so I am confused

but glad you found the problem , fixed it and reported back to us
thank you

[Punch953]

without a ground I do not see how it could have lit up or even a light bulb in it light up when you turned on the key, so I am confused

but glad you found the problem , fixed it and reported back to us
thank you

The gauge illumination had a separate ground from the gauge itself. For the life of me I can't figure out why the tach ground went all the way back to the engine but it did. It was bundled with the trim indicator wires.

[99yam40]

good info, thanks

[boscoe99]

The gauge illumination had a separate ground from the gauge itself. For the life of me I can't figure out why the tach ground went all the way back to the engine but it did. It was bundled with the trim indicator wires.

The source of the ground is the motor. From the battery really.

Battery cables to motor. Positive and negative. From the motor both the positive and the ground go from the motor up to the dash via the ten pin main engine harness. To start the motor. For ignition to the motor. To power the instruments.

[boscoe99]

zbat.jpg

Graphically it looks like this.