Replacing a tachometer

I am in the midst of replacing a tachometer and have read that
it is imperative that my tach runs off the rectifier/regulator of my engine- a 1985 Evinrude 140 hp. My original tach was part# 174207. I am replacing with
part #175643-03-B-U. Is this tachometer compatible? I don't want to rewire
from the coil since the unit is already powered through a harness at the control box.

Thanks,
Sal Siosa

Re: Replacing a tachometer

Sal, to some of us, the part numbers mean nothing (getting old, memory, that sort of thing).

We do understand the tachometer must run off of the engine's charging system.

What color wires lead out of your new tach, and if no wires..... what are the terminals marked. Does the new tach have a dial that can be set to #6, or what type of variation setting does it have?

Re: Replacing a tachometer

Edit

Re: Replacing a tachometer

Hi Joe-

Just reposted additional info

Thanks,
Sal Giosa

Re: Replacing a tachometer

Hi Joe-

The wires coming from the harness that led to my old tac are black, purple, grey and blue. The wires were self contained inside the tach so I had to cut then from the tach body. The old tac was an OMC. The new tach I am planning to purchase (I don't know if the terminals are coded-they think it is an OMC- it is an older model but is new- meaning never used) has four terminals on the back to connect those wires. They claim that this is a 0-7000 RPM tachometer for use on 5-6-10 pulse outboards or pulse OMC Sea Drive engines. It does have a dial on the back for settings. BTW- does my engine have an alternator?- another tach I was interested as
my second choice requires that it runs from the alternator.

Thanks,
Sal Giosa

Re: Replacing a tachometer

you can probably terminate the ends of all those wire with ring terminals and nut them onto you new tach

Black: will go to GROUND( or an abreviationg of ground)
Blue: will go to the lights( or the stud that connects to the solder path running to the light bulb)
Purple: will go the stud marked IGNITION (or the abbreviation of it, maybe ING)
Gray: will go to the stud marked SENDER or SEND


you may need to jumper the ground and the blue to another gauge to make sure it is online.

good luck

BOB

Re: Replacing a tachometer

Thanks Bob. I appreciate your input.

Re: Replacing a tachometer

The 140hp has an alternator. Set the tach to number six (6), and the wiring connections as Bob states.

Re: Replacing a tachometer

Thanks Joe for that information, and for taking the time for responding