1996 Johnson 90, Harness in Tach blows fuse in motor

[toolmankan]

I recently purchased a 1986 Boston Whaler Montauk with a 1996 Johnson 90 v4 on it. After some love, the motor finally started (it had sat for 2 years). The tach wasn't registering, and I noticed that the 8 pin harness wasn't plugged into the back of the tach. I plugged it in and the 20 amp fuse on the motor blew when I reconnected the battery.

Question #1: Does the harness have to be plugged in for the tach to read (i know the warning lights won't work)?

Question #2: Any ideas about the fuse blowing? I guess a short in the wiring somewhere. Could the tach be bad? Any examples you've encountered/lessons learned?


Thank you all for your help. I've already accomplished some repairs from reading these posts. Very helpful.

 

[ezeke]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

It could be that the eight pin plug has beeen wired incorrectly or that there is a short. The plug provides the circuits for all of the system check lights on the gauge as well as the tachometer function, so it needs to be checked carefully.

Click the thumbnail to see where the eight wires connect on the plug; you need one through three for the tachometer.

 

[toolmankan]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

Thanks ezeke. I'll check that diagram and compare to mine as wired from the harness plug to the motor.

How would I detect a short in the wire? I've tried light testing for some current out of one of the pins while the motor is running, but I got nothing. Or wait, maybe I haven't done that. I must have meant to, because I can't actually recall doing that. OK, so I'll light test tonight and compare existing wiring to your diagram. The how to detect a short question is still valid, however.

I got my nav lights re-wired and working last night, so I'm making progress. I really appreciate all of you insight, and you willingness to reply.
Thanks!

 

[toolmankan]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

i couldn't find any shorts. I'm going to try testing the rectifier and a couple other scenarios that could be causing that fuse to blow...
I have power out of the purple line on the harness when the motor is running. When I turn the key to the one position (without turning the motor over), the fuse blows in about 5 seconds.
Any other ideas...?

 

[ezeke]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

I don't think that your problem is caused by that system check circuit. When you turn the key to the run position, you are turning on your positive accessory vloltage to everything that is connected to the ignition switch except the primer solenoid and the starter solenoid. You need to check everything that is normally getting a charge from there.

The wires in your main harness are not designed to run accessories such as radios, pumps, running lights, etc. so its easy to overload the circuit if someone has attached a lot of junk to it. Start by disconnecting the items that draw a lot of power and you should find what is causing the short.

You could also just have a bad ignition switch, there are plenty of those around.

 

[z71hunter]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

I'm sorry for jumping into this conversation. But I am having a situation with my 1996 johnson motor also. The diagram that you posted is great. Is there any way to get the other end of the wiring diagram I need to know where the check engine wire is going pin 7..... It comes and goes off and on. Very annoying I appreciate it!

Z71hunter

 

[ezeke]

Re: 1996 Johnson 90, Harness in Tach blows fuse in motor

The diagram came from an owner's manual found here: http://faria-instruments.com/site_manuals/IS0164_B_SystemCheck_commander_tachometer.pdf