OK, close enough for jazz; the tach isn't driven by the alternator,
unlike my Universal, where it is. Ah, well, one less wire to mess
with. [grin]

TNX!!

Cheers,
   Rick Emerson

Richard Cassano wrote:

> Rick,
>
> On the Yanmar 4JH-TE the tach is driven by a sensor screwed into the
> engine block near where the flywheel is located, (port side). As the
> flywheel spins the sensor picks up the revolutions. The alternator is
> not used for this purpose on our engine. One interesting caution: Do
> not mess with this sensor by tightening it or loosening it to
> investigate how it works. This is something I love to do and it always
> gets me into trouble. The tach sensor is precisely positioned with a
> feeler gauge and this adjustment can only be done with the bell
> housing pulled away from the engine. I do not have my manual in front
> of me so the exact location of the sensor is just from memory when I
> had to separate the bell housing last year to replace the damper
> plate. It wasn't until after the job was done that I read about the
> tachometer sensor adjustment. If I had known, I would have checked the
> gap while it was convenient.
>
> I had my old 120 amp "AmpTech" alternator rebuilt by Great Water in
> Maine and it came back looking brand new.
>
> Rich Cassano
> S/V Gray Eagle (finally, with wet feet)
>
> Richard B. Emerson wrote:
>
>> A friend's alternator let go over the weekend and now he's ready to
>> install a new alternator on his Yanmar 4JHE. He asked me to do the
>> wiring and I'm good with that save for one loose end: whether new
>> alternator has the same number of poles - which affects the tach
>> reading. When I mentioned this, I was told that after the alternator
>> failed (windings shorted out - lots of smoke and sparks, I'm told),
>> in order to get home, the alternator was disconnected but left in
>> place so the waterpump drive would still work. And the tach also
>> worked. Either the tach is driven by a pickup on the crank or...?
>> Anyone know for sure about this?
>

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Received on Tue Jun 6 20:33:29 2006