Tacho connection on Mercontrol

[johnrob]

I have an old Merc (650SS) about 1969-70 and I need some information on the Tacho signal. The tacho wire is connected to the power pack in the motor. Does it produce one pulse per revolution or is it one pulse per spark (4 sparks per rev)?<br /><br />I know some tachos use the stator pulses (3-4-5 per rev) but this one looks like it generates a pulse from the ignition circuit.<br /><br />Anyone have any idea?

 

[mellowyellow]

Re: Tacho connection on Mercontrol

on my '70 1150 the tach signal comes from the<br />rectifier and runs directly to plug on front<br />of mercontrol. other side of rectifier charges<br />the battery. a new one is about $35 and they'll<br />try to sell you a lil mounting bracket for $8<br />that mounts the new style.<br />good luck,<br />M.Y.

 

[rickdb1boat]

Re: Tacho connection on Mercontrol

As, Mellowyellow said, That's the way my 67' 650 was, too. I would take his advice on this.

 

[johnrob]

Re: Tacho connection on Mercontrol

Thanks for the advice.<br /><br />The tacho wire on the Mercontrol is definitely connected to the ignition box. The reason I need to know the pulse frequency is that I want to connect a digital tacho and therefore need to know the number of pulses per rev.

 

[Trent]

Re: Tacho connection on Mercontrol

I believe this is what your looking for?<br /><br /> Tach Settings

 

[johnrob]

Re: Tacho connection on Mercontrol

Thanks<br /><br />They say to move the wire in the powerhead from the ignition unit to the rectifier. However, they don't say which wire on the rectifier - mine has a red (DC+) and two yellows (AC). <br /><br />I assume they mean to connect to one of the yellow wires (I know it doesn't matter which one as it's AC from the stator/alternator)? Unless someone knows different??