1982 70hp Evinrude loss of power under load, max 2500rpm

[ctswf]

Hello, my motor is a

70hp Evinrude outboard
Year: 1982
model: e70elcnb

This year it has a new issue with loss of power under load, full throttle only hits 2500rpm and 10mph.

It also sounds like it's idoling a little lower than usual.

It can stall on me, but mostly it will run fairly stable, but only hitting this slow speed max. While cruising at this full throttle but slow speed, it might burst higher power up here and there, almost like it's clearing out a clog, but usually will return to this lower rpm.

The gas and fuel line w primer bulb have been changed.

The carbs and fuel pump have not been addressed yet. Does this sound like a probable carb or fuel pump issue?

The motor still starts and runs great in the driveway. I just can't get the high speed anymore.

I realize this is a common question, hoping maybe these "bursts" of power are a hint to the cause. For example at one point during the issue it randomly opens up and ran full speed for a few minute's straight before bogging back down again.

Thanks.

Linkages seem normal

 

[racerone]

Do not run the motor any more until you fix the issue !!-------Remember a plugged carburetor stops fuel to one cylinder.---Then that cylinder does not get the correct amount of oil either.-------Does spark jump a gap of 3/8" or more on each lead , yes or no ?-----What are the compression test numbers ?

 

[ctswf]

Thanks so much,
I should have known to check the basics!
​
There is no spark on the bottom coil.

The top 2 coils do have good spark.

Compression (from top down) is 125,125, 122.

I bought this motor dealer rebuilt 15 years ago so they are at least that old.

Should I just change all 3 ignition coils or should I also be worried about what comes before it, power pack is it called?

Any idea what this brown rectangle box is to the right of the coils, the coil wires mould in to it.

Pic
https://imgur.com/a/mYVrCNh

Edit: ok I see that brown box is the power pack. Should I be replacing this as a precaution?

 

[racerone]

That brown box is the powerpack !

 

[ctswf]

Ha, I just figured that out and edited it same time as your response. Worth changing it? Or leave it until it's bad, assuming it's not already

 

[racerone]

They are not expensive and many folks do like to change them out on a hunch that it is bad.

 

[ctswf]

Thanks, I'm gonna swap some parts out and report back

 

[ctswf]

So my problem was no spark on the bottom ignition coil.

I swapped all 3 coils and also the power pack.

However that bottom "bad" coil, the new replacement can only jump 1/4" where the other 2 (new) which never had a problem can still jump a strong 3/8

Previously if I sprayed sea foam in that carb while running there was no effect on that bottom carb because no firing.

Well it does bog down and smoke when I sea foam it so all seems well, and the motor can hit higher rpms in the driveway, and I THINK sounds better at idol.

But what's the deal w a weaker spark, and is that bad? It definitely appears weaker than the other 2.

No in water trial yet

Edit:
I did swap the boot wires w no change. However I saw some arcing out of the boot where it connects to my tester. It arced over to the motor housing. Possible bad ground on my tester clips or bad boots? Swap wires still shows weak only on bottom cylinder

 

[racerone]

It will rev up in the driveway running on 2 of 3 cylinders.----Thus not a good trouble shooting test.------Take some ohm readings on the charge coils and sensor coils.----No need to remove flywheel for those readings.

 

[ctswf]

Bear with me as I try to google these things... Here's a Pic I just took. I believe I am testing the charge coil of the stator? 0.58 ohms

https://imgur.com/a/wH6yjmb

What is the sensor coil?

 

[racerone]

588 ohm sounds correct.------Sensor coil wires might be in the other plug in connector.

 

[ctswf]

I'm still un sure what the sensor coil is. But I'm assuming it's the only other wire (2 leads) coming off the stator?

Those 2 other leads go to the Rectifier.

So the charging coil wire coming off the stator reads 0.58 ohms
The other 2 leads read 2.8 ohms
The Rectifier itself disconnected reads 0.60 ohms


I think when I tested "other 2 leads 2.8ohms" it was all still connected battery and all.

I cleaned up some connections between these devices (terminal block, not a plug). Some rust

Its day time so harder to see but it for sure does get spark and idols better than it was so if not fixed its surly improved. I think I'm gonna go for a test run.

 

[racerone]

No-----The yellow wires going to the rectifier have to do with charging the battery !!----Does your stator read .58 K ohms as per the picture.-----That is = to 580 ohms.------I am reluctant to reply to electrical questions since 12 volts / wires are just too confusing to some !----Sorry.

 

[ctswf]

Yes the picture 0.58k is connected to the plug coming off the stator

 

[ctswf]

Thanks racerone!!!

Not sure I took those readings correctly, but everything is performing great. Went out for a few hours on the water.

30mph 5200rpm. That's the performance I'm used to w my setup, ran solid as a rock.

I'm unsure why the bottom coil cannot jump as far a spark test as the others but it did 1/4" fine. I have since cleaned connections before the ride and have not retested the spark test but either way I appear to be fixed.