1977 Johnson 115 HP will not WOT

[smm96sam]

Re: 1977 Johnson 115 HP will not WOT

You are awesome ezeke! Thank you. Will it hurt if I adjust the throttle cable just enough that the engine doesn't die when I put it in gear until I can get a tach?

 

[smm96sam]

Re: 1977 Johnson 115 HP will not WOT

I installed the tachometer and took the boat out yesterday. The tach didn't work. I checked the wiring and got 12 volts. Without the motor running I son't get anything on the grey wire. I installed the grey wire to the tach wire coming into the control box, ignition wire to the purple post on what looks like the hot horn (I got 12 volts) and the ground wire to the fuse panel ground. Did I do something wrong? Also, the tachometer needle is set on 650 RPMs. Is this right?

 

[ezeke]

Re: 1977 Johnson 115 HP will not WOT

The gray wire needs to be connected to the terminal block at the engine, and the rectifier has to work or the tachometer will not work. Be very careful not to let stray voltage ride the gray wire or it will cook the rectifier.

Notice in the diagram that 6 and 7 are bridged. The signal comes from that union of the alternator and rectifier wires so they need to be connected as shown.

BTW, there is no "rpm setting" on a universal outboard tachometer, just a dial that needs to be turned to 6p.

 

[smm96sam]

Re: 1977 Johnson 115 HP will not WOT

Thanks ezeke. Isn't the grey wire in the control box the one that runs to the terminal block? Since the guage needle is stuck on 650 could that be a sign that the tach is bad? At least the light comes on when I turn on the switch.

One more, if the rectifier is bad, will it affect anything else on the engine other than the tach?

 

[ezeke]

Re: 1977 Johnson 115 HP will not WOT

If the rectifier is bad the battery is not being charged.

Sometimes when a rectifier goes bad, the wires inside the potting fuse and allow the battery voltage to go the wrong way and reach the stator. That will melt down the stator. It can also cause an engine fire.

 

[whitejamie99]

Re: 1977 Johnson 115 HP will not WOT

There is an excellent procedure by Joe Reeves for setting the timing. Search this forum for Joe Reeves WOT timing and you will find it. For this motor the timing should be set to 24 degrees using Joe's procedures. Normal timing is 28 degrees and you subtract 4 degrees for Joe's methodology.

Correct?

I had the exact same problem and decided to replace the timer base, power pack and wiring from remote through the engine harness. This engine is 34 years old.

 

[smm96sam]

Re: 1977 Johnson 115 HP will not WOT

I installed the tachometer and took the boat out yesterday. The tach didn't work. I checked the wiring and got 12 volts. Without the motor running I son't get anything on the grey wire. I installed the grey wire to the tach wire coming into the control box, ignition wire to the purple post on what looks like the hot horn (I got 12 volts) and the ground wire to the fuse panel ground. Did I do something wrong? Also, the tachometer needle is set on 650 RPMs. Is this right?

I just want to check with the experts to see if I hooked the wires up right. The purple wire is hooked up to a purple wire on what looks like the hot horn (I get 12 volts). I hooked the ground wire to my fuse panel groun post, and the grey tach wire to the grey tach wire in the control box. Is this okay? The tach still isn't working. If the wiring is okay, I will look at replacing the rectifier but I just want to be sure I have it wired okay first. Help!

 

[ezeke]

Re: 1977 Johnson 115 HP will not WOT

I just want to check with the experts to see if I hooked the wires up right. The purple wire is hooked up to a purple wire on what looks like the hot horn (I get 12 volts). I hooked the ground wire to my fuse panel groun post, and the grey tach wire to the grey tach wire in the control box. Is this okay? The tach still isn't working. If the wiring is okay, I will look at replacing the rectifier but I just want to be sure I have it wired okay first. Help!

Did you verify the correct connection of the gray wire at the terminal block? There should be very little or no voltage reading on the gray wire with the engine not running. You may also want to check continuity from the terminal block to the tachometer.

When the engine is running use your AC voltage meter to test between the sender and the ground at the tachometer. The voltage should read a minimum of 5 volts AC with the engine running.

When you first turn the ignition key from off to the run position, the tach should snap to zero.

Poor tachometer performance is often traced to weak ground connections.

 

[smm96sam]

Re: 1977 Johnson 115 HP will not WOT

Thanks ezeke,

I installed the new rectifier today and the tach still didn't snap to zero. I tested the grey wire at the terminal block and got the lowest reading (I think 0.01 something like that) Should I run a jumper from the terminal block to the tach to see if the grey wire is bad or is it more than likely my ground? I have the ground wire on my fuse terminal rather than the ground post on the control box. Is that okay where it is?