RPM on a 1970 85hp

[smoke14]

Im looking to upgrade my prop, I need to know what rpm the engine is turning but there
is no tach hooked up. Can anyone tell me how to hook up a tach to this motor.
It is a 1970 Johnson 85hp with the electric shift.

 

[fireman57]

Re: RPM on a 1970 85hp

Do a search on here for tack installation and there are a lot of threads on it.

 

[ezmobee]

Re: RPM on a 1970 85hp

On my '73 there was a gray wire in the control box that is the pulse feed for the tach. Not sure if it's the same on your '70 or not.

 

[smoke14]

Re: RPM on a 1970 85hp

Great idea, however there are no threads pertaining to a tach install on a 1970 Johnson 85hp Electric shift.
Im looking for information on what kind of tach and how to install it on the engine! I would appreciate some good direction from people with first hand knowledge on this subject.

Thanks

 

[fireman57]

Re: RPM on a 1970 85hp

Basically the tachs hook up the same on whatever engine. The electric shift has nothing to do with it.

 

[smoke14]

Re: RPM on a 1970 85hp

Basically the tachs hook up the same on whatever engine. The electric shift has nothing to do with it.

You have been a great help, now step aside and let others that have useful information post. I need to know the type of tach needed and how to install it on the engine. According to YOUR search request there are different types of tachs and how they are installed differs from engine to engine. If you want to help Im all ears if your just going to post random useless thought I would ask you just dont post in my thread.

Thanks

 

[Sixmark]

Re: RPM on a 1970 85hp

Do you have a standard Johnson/Evinrude control box with a keyed ignition switch or do you have console controls? If you have a regular control box look just below the key for a plug with anywhere from 1 to 3 wires coming out of it. If you have that plug you can hook up your tachometer to the grey wire.

If you don't have that setup let me know and I will try to find a diagram to post up for you to follow.

 

[fireman57]

Re: RPM on a 1970 85hp

Sorry I have not been any help but being snippy doesn't exactly make someone want to help you. I did a search and found this. If it doesn't help then I promise I will not get in your way anymore cadet.

If you have a 1970s OMC control there should be a grey wire inside of it for the tach. That is the pulse wire from the terminal block at the engine. Then you need a positive line from the ignition switch [purple] and a ground.

 

[emdsapmgr]

Re: RPM on a 1970 85hp

Fireman is correct. If your 70 is like my 72, the control box has a grey wire left cut off inside the control box at the factory. This is the tach signal lead. You will need to find a + and a - electrical source from the dash to run the tach. That grey lead will exit the control box through a special hole drilled between the two control box halves at the underside of the box. Connect it to the "S" pole of the tach. You will need a marine tach. An automotive won't work. Set the tach screw on the back to "6" and it will read correctly for your engine.

 

[Sixmark]

Re: RPM on a 1970 85hp

If you are going to have to open the box to tap the grey wire, then he may as well tap a source for the power as well while he is in there if he doesn't have one already at the dash.

 

[smoke14]

Re: RPM on a 1970 85hp

Sorry I have not been any help but being snippy doesn't exactly make someone want to help you. I did a search and found this. If it doesn't help then I promise I will not get in your way anymore cadet.

If you have a 1970s OMC control there should be a grey wire inside of it for the tach. That is the pulse wire from the terminal block at the engine. Then you need a positive line from the ignition switch [purple] and a ground.

Thanks, now that is information that I can use. I do have the Johnson controls, Ill take a look inside for the grey wire.