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Old 14 September 2009, 16:52   #1
Member
 
Country: UK - England
Town: Hamble
Make: Novamarine
Length: 4m +
Engine: Yamaha 60
Join Date: Sep 2009
Posts: 32
Tacho going backwards

Hi,
I am trying to get my 2000 model year (pre Smartcraft type) Mercury tachometer working with my 1989 Yamaha 2 stroke 3 cylinder 60 hp outboard.
There are four wires coming out of the control box instrument loom. They are:
Green
Black (earth I assume)
Yellow (switched positive?)
Red (Permanent positive)

There are three places to connect them at the back of tacho marked:
Send
Ign.
Gnd.

There is also a dial to adjust the pole setting of the tacho on the back with all kinds of things like 8p 6p 3c etc.

At the moment I have the green wire from the loom going to send on the tacho, the yellow to Ign and the black to gnd. At tickover it reads about 800rpm which looks good, however when I rev it the reading drops to zero rather than going up. I've got it set on 6p at the back as the engine manual says it needs 6 pole tacho.

Is it possible to wire this tacho to this engine or am I wasting my time?
Any idea what I've done wrong?
Hope somebody can help!
Jake
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Old 15 September 2009, 07:07   #2
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610
Jacob,

Welcome to Ribnet.

Firstly, Your Yam wiring colour guesses are correct (well, according to the info I got off the net a while back, and certainly agree with my old '79 vintage 55 Yam colour scheme).
I agree with your connections too. I have a Suzuki Tacho which has told me how fast both the old Yam and the current Merc were spinning, so there should be no reason why it shouldn't work.

A simple test might be to switch it to a different pole setting, & see what happens. It may be as simple as the 6 pole connection on the switch is dodgy or not fully clicked into place. click it back & forth a few times & see if it decides to work. If it works at a different pole setting, but tells porkies in the RPM dept. - that would at least prove the boat wiring is OK.

Most of these "olsdschool" tachos need 12V to run, and basically count the pulses from the alternator, which form memory should appear at >4.5V (AC). Might be worth checking the voltages at the tacho, and clean all the connector pins, as there may be some weird capacitance thing going on.

Only other option is to get a multimeter & check for supply & signal voltages (Supply DC, sigbnal measure it on "AC" setting - it should read >4.5V) and chase it right back to the engine if need be.

Like I say, there's no reason why it shouldn't work.
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