1967 Johnson 100hp V4TL-14 Needs Tach

[exodave]

Can someone tell me if I need to use a specific kind of tachometer for this engine? The installed one doesn't appear to have worked in a looong time, and it sure would be nice to have a working one. I see some old teleflex tachs for cheap on ebay, but not sure if they will even work. Thanks!

 

[boobie]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

You might try Tiny Tach.Com. Stay away from ebay 'cause you never know what you'll get.

 

[tblshur]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

exodave, if you havent already, i would check wiring to make sure its good to tach before buying new one. good luck!

 

[racerone]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

The tach runs off a signal from the alternator.--Is the battery staying fully charged ?

 

[exodave]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

exodave, if you havent already, i would check wiring to make sure its good to tach before buying new one. good luck!

The wiring appears to be good, but I don't know how to check the signal.

The tach runs off a signal from the alternator.--Is the battery staying fully charged ?

Yes, the battery does stay charged.

 

[boobie]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

To check exactly what kind of tach signal you have you'll need a volt/ohm meter with a DVA adapter.

 

[F_R]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

The 1967 100hp has Battery CD ignition, and was wired for a special tachometer that got it's signal from the coil + terminal (300V pulses). Your chances of finding one of those is slim to zilch.

I'm not 100% sure, but I believe the alternator has an erratic output because of the voltage regulator. If I'm correct, the alternator would not be a suitable tachometer signal. I'll see if I have the info on that.

Later.

EDIT: Well, I checked my stuff and I still don't know if you can get a suitable tach signal off that alternator. The electronic regulator monitors the battery voltage and enables/disables the alternator as required to control the voltage. This happens many times a second whenever the motor is running.

 

[boobie]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

That's why I said Tiny Tach .

 

[exodave]

Re: 1967 Johnson 100hp V4TL-14 Needs Tach

The 1967 100hp has Battery CD ignition, and was wired for a special tachometer that got it's signal from the coil + terminal (300V pulses). Your chances of finding one of those is slim to zilch.

I'm not 100% sure, but I believe the alternator has an erratic output because of the voltage regulator. If I'm correct, the alternator would not be a suitable tachometer signal. I'll see if I have the info on that.

Later.

EDIT: Well, I checked my stuff and I still don't know if you can get a suitable tach signal off that alternator. The electronic regulator monitors the battery voltage and enables/disables the alternator as required to control the voltage. This happens many times a second whenever the motor is running.

Thanks for all that info. I did notice the tach output lead coming off the coil + and wondered if that was right. Of course, the service manual verifies this is the right spot for it. I guess, once the motor is back on the boat in a couple months, I'll see if there's any way to repair the tach on the dash. It's a huge crazy looking globe thing as if it came off a 50's Cadillac and covered in badly corroded chrome, but as far as I could tell it was wired as per the wiring diagram in the manual. Maybe all it needs is a good whack.

 

[exodave]

So, I had abandoned the tach to work on other things. Now back with an update. I found this parts diagram for my engine:



And when I pulled the tach off my engine it has part #121614, along with an instructions sticker saying to connect to the alternator. So, it must be the wrong one. Plus, the ground terminal is wired to the ignition switch 12V terminal...

No luck finding the proper tach listed on this diagram anywhere online.

But, I do see this written on the faria outboard tach poles reference chart pdf on their website: Older model outboards (prior to 1977) may have the tach signal wire originating at the ignition system though they are alternator equipped. All alternator tachometers may be used on these systems by disconnecting the tach signal wire at the engine and connecting that wire to the unrectified alternator signal at the rectifier. Be certain the number of alternator poles match the tachometer pole setting of the tach.




So, maybe I can install one of their tachs this way? As in, just tap into one of the two yellow wires from the stator under the flywheel before they pass through the rectifier?

 

[exodave]

ugh, posted multiple on that last one. moderator, please delete this one.