Is Tachometer compatible for 1974 Johnson 65 HP and 1983 Force 85 HP?

[Plainoldguy]

I installed a 1983 Force 85 HP on a 1974 Starcraft that originally came with a 1974 65 HP Johnson. Both motors had a 2-wire connection to the tach/ground. After installing the Force, I hooked up the purple tach wire (and ground) to the two connections for the Starcraft tac/ground. It works (meaning it goes up and down with the throttle), but the readings seem way too high. For example, at idle in neutral (using muffs), the tach is showing about 3,000 and it rises much high higher in forward/reverse gear when the throttle is increased. Does anyone know if the two motors have similar technologies that would make this tach compatible or are the readings too high because the two motors calibrate differently? Both motors have three cylinders.

 

[Plainoldguy]

I just researched and learned the early Force motors had 20 pole tachs. I posted this reply in case someone else had the same question.

 

[GA_Boater]

Number of cylinders don't count like a 4 stroke. The tach may have a rotary switch on the back to match the number of poles in the stator.

One of the Force guys would know what the setting is. It may be 8 for a Force, but I'm not 100% on that.

 

[roscoe]

You need a 20 pole tach.
Very few available at this time.
Some used on ebay, probably not worth the gamble as its likely no good.


Alternative would be an inductive tach like a TinyTach, good for diagnostics, but not for permanent use.

Oh look what I found:

Looks like Sierra does make one yet, google:

Sierra 69044P

 

[jerryjerry05]

There might be a tiny black arrow shaped screw on the back.
You can try turning that but it probably won't help.
Like the others said you need a 20 pole tach.

Faria or Teleflex might make what you need.

 

[Plainoldguy]

Thanks for both of your replies-you guys are the best!

 

[jkoppen73]

as of a few yrs ago, Faria Marine Instruments made a 20 pole tach, I have one in my boat, 1986/85 h.p., but their app list shows 1984 thru 91 force engines, best to call them to verify the their tach will work on a 83/85 h.p.

 

[jerryjerry05]

The 83 is a 20pole too.
The difference between them is the connectors, some were plug in and the others were the screw down type.