Need help with tachometer

[andreipou]

Hello, I got this tachometer with the boat.
I am not familiar with those.
I think it had OMC motor before I put 1979 85HP V4 (85ML79R) on it.
Is there a way to use this tachometer somehow?
What kind of "sensor" does it use?

 

[racerone]

It is a Mercury tachometer.

 

[F_R]

Don't know about that tach, except it won't work on your '79 85hp. You need an alternator tach which counts the pulses from the alternator.

 

[andreipou]

Don't know about that tach, except it won't work on your '79 85hp. You need an alternator tach which counts the pulses from the alternator.

But, the motor has to be equipped with some kind of "plug" or "outlet" for that, right?

 

[racerone]

Some had a plug on the control box.------I can not see or feel your control box !!-----Do not know if yours is a control box from 1973 or 1995 !!!

 

[andreipou]

Some had a plug on the control box.------I can not see or feel your control box !!-----Do not know if yours is a control box from 1973 or 1995 !!!

I think it is later (80s) year.
What is this black rubber plug (3-prongs) ?
It can not be T&T since this remote does not have T&T switch.

 

[racerone]

That be the plug for a tachometer.----I have always said that electrical stuff / wires is confusing.

 

[F_R]

That plug is for a tach. The motor should have a terminal strip on it. Tach connects to the yellow-with-grey-stripe wire, and ground. Both are carried forward to the remote control, assuming it hasn't been tampered with.

Third wire on the plug is for night illumination.

 

[andreipou]

Great!
There is a hope to get tach for it now.
I never had it for my smaller motors, but for this one it makes sense to have.
Tach in the first post has POS, NEG and LIGHT too , but you said it would not work, right?
Can you get me an idea what would be the right one for this? Maybe, pic\image from the web?

I have manual for this motor and manual for the 50HP the remote came with and try to compare wiring with the actual wires inside the control to see if it can be used.

 

[F_R]

I know nothing about the tach you posted. But the tach you need works off an AC alternator, before it is rectified to DC. That's enough to tell me that (+) and (-) DC input don't get it. Maybe someone else knows more than I do. You're welcome to check around.

BTW, you are standing in a store that sells tachometers. https://ww2.iboats.com/Boat-Tachometers/dm/view_id.248010

 

[andreipou]

I did some research.
First, the manual for original 50 HP motor the remote came with says this 3-prong rubber plug can be used for accessories and wiring diagram (pic 1) even calls it "tachometer". Terminal strip on this diagram shows colors you described, so RC part looks good for tachometer hook-up, right?
Second, the current 85HP has also terminal strip and wiring diagram (pic 2 & 3) have similar wires, but no tacho plug because original RC for this motor does not have it, but manual shows "junction box" that is used with this RC, so, maybe, that is why.
So, engine end will work with RC end via red plug properly, right?
I am thinking that this should work if I get cable like this to connect tacho to RC plug, right?

Evinrude Johnson OMC Tachometer Tach Gauge Wiring Harness 174732 0174732 | eBay

Find many great new & used options and get the best deals for Evinrude Johnson OMC Tachometer Tach Gauge Wiring Harness 174732 0174732 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

I found in my scrap box OMC tachometer (pic 4 to 8) that counts pulses (judging on the instructions sticker). I think this one should work on this setup, right?
Just need to figure how to connect it properly: black ground wire goes to "G" , gray (pulsing) wire from terminal strip goes to right sticking wire and I need to shorten C,2,3,4 properly as soon as I figure out number of pulses per revelation my V4 produces.

Am I on the correct track?

Thanks.

 

[F_R]

NO. That tach is for motors that have breaker points and it counts the times the points open per rev. Your motor has no points and a tach for it counts the alternator pulses instead.

BTW, the e-bay tach you found is kind of a rare find.

 

[F_R]

This one should work, less than 80 bucks, brand new. Why go elsewhere?
Disclaimer: I have no financial interest in i-boats. Verify fitment before purchasing.

Complete Boat Gauge Sets - iboats.com

Complete Boat Gauge Sets - Since 1998, iboats is the most trusted water lifestyle online store for boat parts and accessories, boats for sale, and forums. Enjoy great priced products with fast shipping.

ww2.iboats.com

 

[andreipou]

NO. That tach is for motors that have breaker points and it counts the times the points open per rev. Your motor has no points and a tach for it counts the alternator pulses instead.

BTW, the e-bay tach you found is kind of a rare find.

It was not from ebay , it was from my box of junk...
Just trying to save a buck.
The boat is 1968 , the motor is 1979.
I am mot going to make it new anyway even if I buy new parts.
Used parts that work will fit fine...

 

[andreipou]

This one should work, less than 80 bucks, brand new. Why go elsewhere?
Disclaimer: I have no financial interest in i-boats. Verify fitment before purchasing.

Complete Boat Gauge Sets - iboats.com

Complete Boat Gauge Sets - Since 1998, iboats is the most trusted water lifestyle online store for boat parts and accessories, boats for sale, and forums. Enjoy great priced products with fast shipping.

ww2.iboats.com

Need to clarify:
Will it work on 2 cycle motor?
It says "4 cycle".
Also, many of them on Ebay say "4 cycle" like the one below.
I guess it makes the difference.

Faira Marine 3" Boat Tachometer Tach Gray Face Silver Bezel TC9983A | eBay

About Zim's Outboard Parts.

www.ebay.com