Mercury 115 Tacho conundrum...

[Superjetjim]

I have a 1993 Mercury 115Hp 2+2

My tacho is not working and so far I’ve done the following but still can’t fathom it out:

1) Installed a brand new Merc Tach
2) Set Switch on rear to number ‘4’ as per shop manual
3) Fitted new rectifier box
4) Ran a direct cable (to bypass the grey wire in the loom just in case that was faulty) - went from Tacho gauge signal > grey wire on engine block
5) Tested the voltage at the gauge and it’s power

I can’t think what else it could be, it’s driving me crazy and spent over $200 so far and no fix.

Please help me guys!

 

[Superjetjim]

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[Superjetjim]

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[Superjetjim]

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[roscoe]

Do you have voltage from the grey wire at the powerhead, when you put meter between terminal and ground ?

 

[Superjetjim]

Do you have voltage from the grey wire at the powerhead, when you put meter between terminal and ground ?

Thanks Roscoe, I can’t get to the boat until the weekend, but ‘if’ I have no voltage there what do you think the root cause would be of that? Maybe a faulty stator?

Jim

 

[Superjetjim]

Any thoughts Roscoe?

 

[Superjetjim]

Further update / request for help please.

I’ve notice if I push the choke in with the key the Tacho jumps into life - as soon as I release the
choke it stops working again - must be something simple surely?

Any ideas guys?

 

[Merc115_1988_6_TS]

Subscribed. I've got a non-functional tach as well. Just logged on to search for debug process.

 

[jimmbo]

Problem with the key switch/wiring in the control box, perhaps. Get a wiring diagram

 

[Superjetjim]

It makes the Tacho twitch for a second when you push the key in (although the Tacho doesn’t read the RPM it just jumps for a second)