will the tach from 1961 johnsons 20hp work with my 1991 40hp johnson

[MudLake]

I may decommission 2 20hp johnsons on my 15 ft starcraft for the 1991 johnson 40 hp which i rebuilt 20 thou over.
My boat has two tachs for my 1961 johnson.
I got the omc control with the 40 hp and it has a 3 pin connector on it for
acc, gnd, tach signal.
I hooked up my fluke meter to the tach pin and it reads about 142.
if 142 low for this engine.
question: will the 20hp tach work with the 40 hp outboard??????????

cheers

 

[F_R]

Re: will the tach from 1961 johnsons 20hp work with my 1991 40hp johnson

Absolutely not. But don't dispair, those tachs are in big demand. They are driven by the magneto, and are no longer made. Somebody wants them.

You need a tach that is driven by the alternator, which is where that grey wire goes.

BTW, 142 volts is way wrong. You probably have a blown rectifier. Should be close to 14 volts.

 

[MudLake]

Re: will the tach from 1961 johnsons 20hp work with my 1991 40hp johnson

Maybe not clear on the 142.

my meter was on frequency so it would have been RMPs