84 Johnson 70hp > Suddenly Died > Recently replaced key switch

[scrampbell]

What's up, my boat motor geniuses?

Replaced key switch over winter after boat wouldn't start at the midway point of my one trip to get oysters, sub 40 degrees in October with no tow insurance. 60 degrees here last Saturday so I took the wife and 2 year old out. Successful trip, but boat died suddenly 500 yards from boat ramp on the way back in.

Seemed to me like somebody pressed the kill switch; it really just suddenly died. Anyway, given that I just had a pseudo similar situation where I had no spark and changing the ignition switch fixed the problem, anybody have any suggestion as to what might be my root cause? I'm thinking the key switch is just a symptom.

Thanks for the help.

 

[5150abf]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Had a similar situation, motor died,pulled hood, fixxed, turned out to be a bad connection.

I have an 80 and the wiring was in pretty bad shape so I replaced most of it and haven't had any problems since.

Check all your wiores really close and change any that look bad, you may stumble across your problem but I would bet it is just a bad wire.

 

[jonesg]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Test for spark... if no spark,
Disconnect the big red harness plug and jump the solenoid, if it sparks then the problem is in the harness/ or ig' switch.
If its got spark then its probably intermittent and you'll have to chase it down. I'd check the switch for loose connectors or bare wires.

I was getting a shock between the shifter and steering wheel, turned out the ignition switch was rotating in the bezel and shorting itself out.

 

[ezeke]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Check the fuse?

The harness wiring is not designed to handle acessories, so if you have them wired to the ignition, you may want to rewire them.

 

[scrampbell]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Excuse the long delay, but I wanted to update you on this... Looks like 5150abf was right about a bad wire/loose connection.

I tested the ignition switch with a multimeter while still installed thinking that some other issue might be causing the switch to go bad and it looked to me like it had gone bad. (turns out that I was really testing how much I know about wiring, because I tested it again after removing and it tested fine.) So I reinstalled the ignition switch and then tested again for spark and I got spark. Finally got it out last weekend for a successful ride.

So I'm blaming a bad connection at the switch that got fixed when I reinstalled. I'm going to try to get through one more season before replacing all the wiring, but I might be pressing my luck -- the tach was jumping around at WOT (+- 500 I listened close and couldn't hear any revving or anything) which I'm guessing means a bad wire/connection somewhere. Right?

 

[ezeke]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

The tach jumping around is probably caused by a bad ground connection -best to correct it before it cooks your rectifier.

 

[scrampbell]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

So I ran into the same problem out on the water last weekend. Boat died suddenly then wouldn't spark but started engaged. I jumped the kill circut and still no spark. So, I'm going to look closer at the wiring. (Is there any other test I should do to narrow down my problem?)

Here's my main question... The way I understand it, when the switch is in the Run position, there's a closed circuit between two of the posts - one ultimately running to the negative battery terminal and one sending the juice to the spark plugs. Then in the "Start" position, you have one additional post joining the circuit that runs to the starter. The fact that I get the starter to engage says to me that the wiring to the negative battery terminal is fine (since the circuit to the starter completes). Am I thinking about this the right way? If so, the main wiring I need to look into is the wiring sending the juice to the spark plugs. And if I have a short in my Tach wiring ground, would this likely be in another location?

As a follow up (and this may be more appropriate in another part of the forum), is there a minimum gauge of wire that I need to use? What about matching existing wire colors? Is West Marine the best place to get the wire? I'm wanting to use materials I have on hand which would mean some general purpose electronics wire (2-wires, Black and White, from RadioShack), but I think the gauge is inadequate for long term replacement.

Thanks again for being so knowledgeable about boat motors and being so willing to help out a clueless noob such as myself!

 

[ezeke]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

So I ran into the same problem out on the water last weekend. Boat died suddenly then wouldn't spark but started engaged. I jumped the kill circut and still no spark. So, I'm going to look closer at the wiring. (Is there any other test I should do to narrow down my problem?)

Here's my main question... The way I understand it, when the switch is in the Run position, there's a closed circuit between two of the posts - one ultimately running to the negative battery terminal and one sending the juice to the spark plugs. Then in the "Start" position, you have one additional post joining the circuit that runs to the starter. The fact that I get the starter to engage says to me that the wiring to the negative battery terminal is fine (since the circuit to the starter completes). Am I thinking about this the right way? If so, the main wiring I need to look into is the wiring sending the juice to the spark plugs. And if I have a short in my Tach wiring ground, would this likely be in another location?

As a follow up (and this may be more appropriate in another part of the forum), is there a minimum gauge of wire that I need to use? What about matching existing wire colors? Is West Marine the best place to get the wire? I'm wanting to use materials I have on hand which would mean some general purpose electronics wire (2-wires, Black and White, from RadioShack), but I think the gauge is inadequate for long term replacement.

Thanks again for being so knowledgeable about boat motors and being so willing to help out a clueless noob such as myself!

The power for your spark plugs comes from the ignition system and has nothing at all to do with the battery, in fact, the engine can start and run without a battery. Relative to the ignition, when you turn the ignition key to the run position you open the kill circuit so that the ignition system can fire. When you turn the key to the start position, the starter solenoid is activated, allowing battery power to run the starter.

http://www.youtube.com/watch?v=LqHPzc2y-YQ

 

[scrampbell]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Thanks for the info and video ezeke... I guess I kinda knew that already. Like I said... thanks for being so patient with all us ubernoobs.

So since I've ruled out the kill circuit, do I need to focus my wiring inspection to the components between the flywheel and the spark plugs then?

 

[scrampbell]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

This may come as a surprise to you all based on what you've read so far, but I want to make sure I haven't done something wrong before I go and replace the stator.

I was going through the tests in the clymer's manual... I disconnected the 4-wire connector between the stator/timer base and the power pack and tested resistance between A-D, B-D, and C-D. Manual said I should get between like 9 and 12 ohms or something on all three and if not then I should replace that stator. A-D and C-D checked out just fine, but B-D read infinity.

I mean ****, does this sound right? Seems like this would only cause loss of spark at one cylinder. But then again, I really don't know much about boat motors yet.

 

[jonesg]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

When it comes to testing $300 parts you are far better off throwing the clymer book aside and getting the genuine factory service manual.
www.outboardbooks.com

You also need a peak reading meter.
http://cgi.ebay.com/ebaymotors/ws/e...0ffce7de7&rvr_id=&ua=WXI6&itemid=380228620129

 

[scrampbell]

Re: 84 Johnson 70hp > Suddenly Died > Recently replaced key switch

Update: Resolved

Replaced the Timer Base due to the test described above ($300) and as expected I still had no spark. Replaced the power pack and finally got spark. Also found a bad ground at two coils which may account for the tach jumping around (?).

It also seems to be smoother now and my theory is that the faulty timer base was causing one cylinder to run rough.

Took the family out for a ride yesterday morning and made it out and back without taking on water, which is what I call a successful ride!