JOHNSON 1993/4 50 HP - Diagnosing ignition problems / testing components

[Zzeke]

Howdy all,

First off, my name is Zzeke and I'm new to this forum. Seems like a great resource, I thank you for that.

We've got a Johnson 50 hp 1994 Model VJ50TLETF S# G03286186 (could be a 1993, boat is a 1994 model)

We got it around 2000 and till 2007, had some issues with it - seems like the oil injection failed, so we premixed for a time. Finally bought a new powerhead for it in 2008 and restored the oil injection.

Current Issue, is that much of the time it runs decent on short rides of say 1 hour or less. Burbles a little on idle, which clears up when we get to the lake and throttle up.

On longer rides though, it'll start dying. Best way to describe it, the engine speed will fade slightly, and then it'll die like you just turned off the key..

So far, it always restarts. It runs on one cylinder then (just by sound / experience). You can then throttle up some at lower RPM like 4000 or a little less, and on the way up both cylinders will fire. If you try to open it up, It'll do the same thing and die. If you try to keep the RPM below that powerband over 4-5000 rpm it will run for a time, then eventually die again.

Once it starts doing this, it seems to run rough at idle, we have even experienced wobbling low speed vibration, what feels like seaweed wrapped around a propeller, only there isn't any and prop is not bent.

So we limp home thru no wake zone, and park it. Later, after cooling overnight and on short local rides, it's OK again, seemingly.

So, that's what it's doing. I'll post a few things below.

Thanks,

Zk

 

[Zzeke]

Fuel Problem? I don't think so.... it doesn't seem to surge or sputter at all.... no evidence of blockage, no smashed primer bulb, filter seems in good shape. No water in the filter.

We've had other outboards (old ones, like 1955) that display some of the same coil behavior - one cyl at low speed, two cylinders at high speed.

I had a Yamaha motorcycle with CDI ignition back in the late 80s. Had a similar problem where it would just die, but after cooling it would start right up. new CDI fixed it.

My dad told me the rectifier box has been replaced once.

So far I have done some rudimentary diagnostics, inspected stator coils and ignition triggers for damage, measured resistances.

I didn't see any damage of any magnets or coils. I could see rectifier has been replaced (no paint on terminals) Rubber at bottom of coil was weather-checked, but it was there.

Coil: Primary range is 0.2-1 ohm, I measured pretty much in the middle, like 0.5/0.6. Output range is 200-400 ohm, both measured 298 ohms.

Stator Charge Coil: range is 450-600 ohms - I measured 704 ohms.

Trigger: range is 35-55 ohms, I measured 26 ohms.

I don't have the DVA adapter (wasn't familiar with it till now) so don't have those readings.

So by the numbers, I've got two of these items out of spec. But are they out of spec enough to cause this problem?

Power Pack.....I did not see any specs for this on the chart I was using.....https://www.outboardignition.com/page40.asp

Is the power pack another name for CDI ignition?

That's all I know for now.

Zzeke