1984 johnson electrical fire

hgullung

Cadet
Joined
May 16, 2006
Messages
12
As I usually try and do monthly I started my motor with the ear muffs attached. I ran the motor for about 10 minutes with no issues and shut her down. I noticed some smoke coming from underneath the cover and it smelled like some kind of electrical burn.

I pulled the cover and noticed right under the back of the flywheel (not sure flywheel is the right term but bascially what the started engages) that there was melted plastic and it was burning. I was not sure what to make of it so i started the motor again for a closer look.

Well the square plastic box was actually burning from the inside and flames started coming out. I killed the engine and started putting some water onto the box and the water started boiling. I could see red embers in this plastic box and it took almost 15 min for it to cool down and stop simmering.

Any idea what the hell happened?

UPDATE: I looked at a diagram it was the regulator assembly that burned up...what would cause that?

Motor is a 1984 johnson 150....i just had it worked on but had started it several times since the service.
 

1fishbone

Chief Petty Officer
Joined
Nov 9, 2010
Messages
476
Re: 1984 johnson electrical fire

Only a guess:
(in order)
Wire coatings get brittle/crack and touch the ground.
Power packs can loss their seal and arc out.
Short in the electrical system (no fuse) and it rails (max out)

The power pack may have been the bomb...something set it off..or it went off on it's own.

Sorry for your loss...seriously, not joking.

Look up 'top secret' or 'Adults only'
He put together some good diagnostic links.
This will help check everything else.
 

Tim Frank

Vice Admiral
Joined
Jul 29, 2008
Messages
5,333
Re: 1984 johnson electrical fire

I was not sure what to make of it so i started the motor again for a closer look.

Any idea what the hell happened?

.

I won't ask why you did that...:eek:... but next time I would suggest that you don't start it again.

Good advice from 1FB.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 1984 johnson electrical fire

It is possible that this engine is a 150S model. That engine has the vented flywheel with the 35 amp alternator. That model uses a combination rectifier/regulator which mounts in the top of the block above the block water cavity for cooling. You are dealing with a lot of amperage on this model. It is not unusual for these r/r units to fail. When they do fail, they catch on fire. Lots of smoke and heat, but hopefully no significant damage to the powerhead. You need to inspect the reason for the fire and repair it before you use that engine again.
 

kfa4303

Banned
Joined
Sep 17, 2010
Messages
6,094
Re: 1984 johnson electrical fire

errrr...yeah, not to rub it in, but water on and electrical fire is a no-no. glad you're ok. hope you can get her going again.
 

hgullung

Cadet
Joined
May 16, 2006
Messages
12
Re: 1984 johnson electrical fire

Guys thanks for the all the advice...I think it is time for a newer motor...tired of spending money on this old guy....just spent 1K getting carbs redone, new starter...thing is barely worth that.

If you live near Houston and want a motor let me know.
 
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