Tachometer Problem on a 90HP Johnson

[Margarita Man]

I just bought an older boat with and '85 model Johnson 90hp and my tachometer reads over 7,000 rpms at WOT which would have blown the motor. Before I buy another tach is there anything in the motor that could be causing this false reading or is the problem with the tachometer. The motor runs real good but I cannot check my true WOT with this whacky reading.

 

[Barnacle_Bill]

Re: Tachometer Problem on a 90HP Johnson

Look on the back of the tach and be sure it is set on 6P. If it doesn't have that setting let us know what type it is and what it does have.

 

[Margarita Man]

Re: Tachometer Problem on a 90HP Johnson

Thank you bhile, I will check it and get back to you.

 

[Margarita Man]

Re: Tachometer Problem on a 90HP Johnson

Bhile,
Followed your advise and got the tach working. I am getting 5000 rpm on WOT and 35 mph on a 17' CC with the 90 HP Johnson. I will try another prop when I can aford it. Thanks.

 

[Margarita Man]

Re: Tachometer Problem on a 90HP Johnson

Bhile,
Followed your advise and got the tach working. I am getting 5000 rpm on WOT and 35 mph on a 17' CC with the 90 HP Johnson. I will try another prop when I can aford it. Thanks.