Tach connections on 1964 Merc 650

[ToddinTO]

Hi,

I have a Merc 650 (serial 1690905 circa 1964) on a 15foot fiberglass hull. It currently has a two blade prop, which I would like to replace with a 3 blade (better for tubing/water skiing).

In the Seloc manual it states that WOT on the engine should run between 4800 and 5200 RPM. I am looking for a prop that will allow the engine to run at about 5000 RPM. The boat does have a tach but it looks like it is disconnected (no wires are running to the engine from the gauge).

I assume that it must be connected to the distributor/magneto in some manner to measure the pulses per second, but I don't know where.

Any suggestions would be appreciated. The service guide I have states that most shift boxes have a connector on the front for a tach connection, but mine, based on it's age does not seem to have one.

Thanks for any/all suggestions.

 

[Yepblaze]

Re: Tach connections on 1964 Merc 650

Assuming (without looking it up somewhere) you have a Magneto there could be 2 different methods of attachment.

One uses the magneto kill wire and 12Vneg to run the appropriate tach sometimes one with different settings or stated that is is capable for use on "12 poles". a term describing how many pulses per revolution

And the other would use the stator or charging coils under the flywheel again with the appropriate tach unit.


Normally, and...

If all is as it has been for years, I might assume that all that might be missing is a wiring harness that plugs into the plug in the forward end of the controller and provides the 2 wires to run to the tach you have.