72 Johson 50 HP no spark

[robtown]

I bought a project boat last weekend (first boat ever) and it has a 72 Johnson Electric start Long shaft.

The guy said he blew the starter fuse and left the key on so it didn't have any juice. Motor seemed to have good compression and the ignition coils look brand new, it seemed like it was worth the 250.00 I gave for it.

I got it home and discover the fuse was fine, and the battery was charged. The motor wouldn't turn over because the neutral indicator (on the motor block) wasn't completing ground, got past that, it turns over good now, but no spark at all.

I noticed the red wire on the reticulator was chafed and exposed, replaced it. Took a wild guess and replaced the power pack, still no spark.

I broke open the control box last night and the neutral indicator switch in there was a mess (but it still allowed it to turn over) I've got it straight wired now.

I don't have an ohm meter (and wouldn't really know how to use one) but It appears that the ignition switch is working properly, and I think I'm getting some power to the power pack, it's just that the orange terminals never fire. (yes I tried with the black yellow disconnected as well)

Stator? Timing Base? Am I missing a possible ground/kill switch somewhere? Do stators totally die or should I be getting a weak current from it?

 

[rickdb1boat]

Re: 72 Johson 50 HP no spark

Disconnect the large red harness connector in the motor compartment. Then jump out the selenoid and see if you get spark. That will narrow it down to a wire/kill switch problem...

 

[robtown]

Re: 72 Johson 50 HP no spark

little daft here. I'm good with the jumping of solenoid, but where to disconnect large red wire? You mean the red wire that's always live on the main terminal block, or the main power from battery to the top of the solenoid?

Thanks,

R

 

[rickdb1boat]

Re: 72 Johson 50 HP no spark

I'm talking about the big red plug that comes from the control to the motor. I assume there is one on yours. Like this one:

 

[rickdb1boat]

Re: 72 Johson 50 HP no spark

Also, do you have a kill switch on the control box?

 

[tashasdaddy]

Re: 72 Johson 50 HP no spark

be careful if it happens to start the only way to kill it is to flood it with the manual choke on the front bottom left of the engine. it's best to pull the plugs when doing this. ohm meters are only $10.00 at walmart. just blew my old one up and replaced it.

 

[robtown]

Re: 72 Johson 50 HP no spark

Ahhhh....
Mine is big and yellow. I don't see a kill switch anywhere on the controls, just an electric choke. Like I said the gear select switch inside the control box was a mess, the insides have frozen in place and the little arm had broken from the base. I have it straight wired right now.

No worries about it starting, no fuel, haven't got that far I want to see a spark. I know it's got decent cmpression...

I'll go get that ohm meter, I'll be back with questions on how to use it, I'm sure.

Thanks.

 

[tashasdaddy]

Re: 72 Johson 50 HP no spark

when you unplug the red(yellow) plug it totally disables the remote control.. you can use a charged battery, using jumper cable, neg. battery to block of motor for ground, positve battery to the big post on the starter with the red wire going to it. the engine should turn over. with some help you can test the spark this way. don't clamp the cable to the starter just touch it. and don't burn the starter up cranking to long. going to cut grass, wiil check back.

 

[robtown]

Re: 72 Johson 50 HP no spark

Update:
Unplugged big yellow plug and turned over. Got a reading of approx 6 volts AC on the yellow wires coming off the stator to the rectifier and 64 volts AC on the brown wire to the power pack. Looks like the stator is bad?

My volt meter does have an ohm meter on it, but I don't know how to use it.

 

[Walker]

Re: 72 Johson 50 HP no spark

Is your volt meter "peak voltage" capable?? If not then your 64vac really means nothing. You need a peak voltage reading.

 

[robtown]

Re: 72 Johson 50 HP no spark

Using a Fluke T5-600 set to autosense (AC/DC) I don't know if it's a peak reading or not.

 

[Walker]

Re: 72 Johson 50 HP no spark

Okay, dug out one of my old manuals and to test for charge coils(stator) you check resistance between brown and brown/yellow wires from stator. Correct reading will be 870-930m ohms.
The sensor coil test (timer base) is a resistance test also. Resistance between the common (black/white stripe) and each of the leads (white/black stripe) should be 7.5-9.5 ohms.

 

[robtown]

Re: 72 Johson 50 HP no spark

Ok, so bear with me here. I'm going to buy a service manual for this motor tomorrow.

But, anyway, when I set the meter to Ohms and touch black lead to earth, and red lead to stator yellow 1 and stator yellow 2 I get a reading of 895 or so on both, and around 900 on the brown lead. Do the same thing on the timer base leads and I get around 200.

Am I doing this correctly?

 

[Walker]

Re: 72 Johson 50 HP no spark

Test the brown leads resistance to each other, not to ground. Same with the b/w - w/b leads.
Sensors (white/black) should have zero continuity to ground.

 

[robtown]

Re: 72 Johson 50 HP no spark

Had to remove the flywheel to find the brown/yellow wire (it's just a ground wire for the stator) unhooked it and the solid brown wire from the power pack, tested these two wires for resistance and it reads 894 +/-

Unhooked black/white and white/black and checked for resistance, goose egg (0), nada, nothing... Zero continuity to ground as well on these.

This leads back to one of my original hunches, that there is voltage coming to the Power Pack, but the mechanism that tells it to fire the plugs is not working (timer base).

Is there another test I can do on the timer base before I run out and get a new one?

 

[tashasdaddy]

Re: 72 Johson 50 HP no spark

go to 'boatpartstore.com' around page 29-30 of their engine faq. is elect testing