Mercury 115 outboard 2 stroke tach problem

[benkitto]

Hi all,
Got a mercury 115bhp 2 stroke with faria tach

Tach was working fine until recently and appears to be dead now

Have checked the following

1. Voltage at idle is about 12.4 volts rising to about 13.4 volts when running engine faster than idle. This tells me the rectifier is working properly I think?

2. Have replaced the tach with an alternative, it wasn't new so to sure if it was working ok, still not working

3. Tach is wired correctly I think.

4. Replaced with new tach tonight and it read 1000 volts at startup and then slowly climbed to 3000rpm at idle? Poles was set at 1 for a 4 cylinder engine.

Was the correct pole setting applied.

WHat can I do to sort my problems out as its very frustrating
Thanks

 

[Barnacle_Bill]

Re: Mercury 115 outboard 2 stroke tach problem

Tach should be set for 6 pulses or 12 poles.

 

[Silvertip]

Re: Mercury 115 outboard 2 stroke tach problem

Outboard tachometers use the pulses from the charging system as the "sense" signal. A 12 pole alternator produces 6 pules which is what your tach should be set for. It doesn't matter if the engine has 1 cylinder or 12. If it has a 12 pole alternator the 6 pulse setting is correct.

 

[benkitto]

Re: Mercury 115 outboard 2 stroke tach problem

Outboard tachometers use the pulses from the charging system as the "sense" signal. A 12 pole alternator produces 6 pules which is what your tach should be set for. It doesn't matter if the engine has 1 cylinder or 12. If it has a 12 pole alternator the 6 pulse setting is correct.

Thanks for the reply

How do I tell if my alternator is 12 pole?

Thanks

 

[Texasmark]

Re: Mercury 115 outboard 2 stroke tach problem

Thanks for the reply

How do I tell if my alternator is 12 pole?

Thanks

If you have a 4 cyl 115 2 stroke it is 12 pole. Manual says so.

Mark