Airguide tach for ’79 Evinrude 35 question

[wetwillie]

Is there any way that I can wire a model 690, 691, 692 Airguide tach to work on my ’79 Evinrude 35?
According to the box, it is for a ’69 & ’70 OMC 33-115hp motor. Fwiw, I also have the module.
Also, IF this tach is not compatible with my motor, can someone respond with what model WILL work with it?
Or, can someone recommend an analog tach that will work?
Thanks in advance,
W Willie

[jerry-ahrens]

I don’t think your old Airguide tach will work. Does your 1979 engine have a charging system? Look for the charging system rectifier located on the Starboard side of the powerhead. it’s a small round piece with a grey, red,
and yellow/grey wires coming out of it. If it has charging capability, the harness tht runs up to the ignition switch should contain the grey ”signal” wire within. Look up a modern tachometer that’s suited for a 2 cycle gas outboard,
and your set. FWIW, on the back of the tach, you will have a grey signal lead, a black engine ground lead, and a red positive (hot) lead.

[frankr]

If it has a charging system, the tach setting would be 5 pulses (10 pole). It works by counting the AC pulses from the alternator. Most modern tachs work this way.

Your Airguide seems odd in it’s coverage. I guess it counts the breaker points openings. Those old style breaker points tachs are getting hard to find. Might be better to sell it and buy a new one.

[Mumbles]

Near the end of this file, it explains how to wire in the 690 tach.

Until my caffy kicks in, it’s your call whether it’s compatible with your motor or not. ☺

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Attachments:

Airguide Tachometer Application Guide.pdf

[frankr]

So, according to mumbles’ chart, you would jumper 1, 3, and 4 for an alternator system. One problem I see there, is it doesn’t say how many pulses, 5 or 6. It would give a reading, even if wrong number of pulses, but would be an incorrect reading if pulses are wrong.

And of course, this goes back to the basic question: Does your motor have an alternator / charging system?

[garry-in-michigan]

Yes it does – number 6 is the rectifier – – – 😉

[frankr]

That diagram covers both, electric start and rope start models. As pointed out by the description for #6.
#6 — 581778 — RECTIFIER ASSEMBLY. ELECTRIC START MODELS (1 required per assembly). So, we still do not know if it is electric start (with alternator) or not. Yes or No.

[wetwillie]

Good evening guys. Thanks for all the responses. My motor IS an electric start model.
After reading Jerry’s initial response, I thought I’d be wise to list the tach and buy another one that works. Now, having read the other responses, I’m glad I didn’t. Fwiw, I bought it for my ’56 Feathercraft that I’m trying to keep at least somewhat period correct.
Am I correct in assuming that the jumping that was described is done inside the case? If not, I’m clueless as to where else I’d be doing this.
THANKS

[frankr]

On the transmitter? (Does it have one)?

[wetwillie]

Sorry Frank, but I’ll have to plead ignorance on this one. The tach came with a module but the circuit is inaccessible as it is potted. Otherwise, where is the transmitter located, if present, and what does it look like?

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