Tohatsu M25 and tachometer problem

[maksio]

Hello dear!
Can anyone help solve the electrical puzzle?
The following components:
A: Tohatsu M25C2 engine - only 2 white and yellow wires
B: Tohatsu M25C3 engine - 3 wires white black yellow
C: Original Tohatsu tachometer - two white and yellow wires
D: Tohatsu tachometer original - 3 wires white light green yellow
And now:
engine A tachometer C - works great
engine A tachometer D - works great
engine B tachometer C - does not work properly - from 3,000 rpm the display jumps sharply
engine B tachometer D - the same!
the last two connections - no connection version works correctly
Does anybody have an idea?

 

[pvanv]

You may need a sender unit for the C3. Exciter only, no pulser.

 

[maksio]

Thank you for your answer.
What element do you mean? What "sender unit"?
Where to buy? White and yellow wires are the charging coil. In both engine types.
Each magnet (there are 4) gives an impulse to the tachometer. It is the same in both types of engine.
Impulses to the ignition system in C2 are two elements: a magnetic sensor and a high voltage coil - in C3 it is one coil.
And - I have the impression that this system causes some kind of electromagnetic interference in the charging coil - which falsify the rotation measurement pulses. Just ... how to get rid of it?

 

[pvanv]

Yes. White is alternator signal. Have your dealer contact Tohatsu, or I can do it...

 

[pvanv]

Depends on serial number.

30A4 # 35175~ / 25C3 # 50039~

3P0726790M

TACHOMETER SENDING UNIT

$26.00

 

[maksio]

Thank you!

 

[maksio]

Does it connect in series (to white) or in parallel (between white and yellow)?
Can you help me find a connection diagram?
I am from Poland - access to this part is really difficult ...
Is TACHOMETER SENDING UNIT also needed when the engine has an electric starter with all the original electrical system?

 

[maksio]

I found
https://forums.iboats.com/forum/eng...s/538867-tach-question-for-a-1998-nissan-25c3

 

[pvanv]

That explains the sender for the modern tach on the 25C3. So Yes, that should be your setup. In series on the white wire.

 

[maksio]

Maybe you know what electronic TSU is? Capacitor?? Zener diode? R-C filter? To do yourself. It's not complicated - much simpler than buying from the US to Europe ...
Thank you very much for help

 

[pvanv]

Dunno what's in the box. Sorry.

 

[sparkey504]

here is the service manual if you dont have it already for the M25c3

https://www.tohatsu.com/marine/common/owners_manual/pdf/Toh25C3_30A4_40C.pdf