Tony Merc Tach information

[bobz]

" Tony, Joe suggested you may

" Tony, Joe suggested you may be able to advise me.

I am completing an 1978 Merc. 3.0 I/O conversion to a Johnson 1993 115 HP on a transom bracket.

I would like to use the existing Medallion tach used with the Merc I/O installation.

Here is what Joe Reeves said - "The Johnson outboard sends out a six (6) pulse signal from the charging system to operate the tach (Notice that the back of the Johnson tach has a numbered dial on the back of it which would be set to "6"). What you need to know is what type signal did your previous engine send out, and from where."

"Bottom line.... If your Merc tack will accept a six (6) pulse signal from a charging system, it'll work fine." (End of Joe's quote)

The Johnson tach that came with the OB is set on "6" as predicted by Joe. The existing Merc tach has settings on the back as follows - 1, 2, 3, & 4 and is now set at 2.

You can see the original string with Joe about 8 below this entry.

Do you think the Merc tach will work with the Johnson (accept a 6 pulse sigal) if so, at what setting?

Thanks,
Bob Z. "

 

[tonyob]

"Bob,

I am looking into you

"Bob,

I am looking into your question, and will try to give you an answer later today.

I believe that the tach was connected to the ignition coil or the distributor. This is different from the way the tach must connect to your outboard (to the stator). Some tachs are designed so that they can be used in either application, but I don't think yours is this type.

I will get back to you later.

"

 

[tonyob]

"Bob,

I was talking to a pa

"Bob,

I was talking to a parts dealer who is familiar with Medallion gauges. He says that he is pretty sure you can use that tach on the outboard, in fact he is positive. I'm still not convinced, but I don't think you can do any harm if you try. As for the setting to use, all I can say is that if it works, you have to experiment and see which setting gives you an accurate reading.

"