1977 85 Evinrude intermittent spark on right bank

[Chevyls6]

So I've got a new to me 85 Evinrude that has an intermittent weak spark on the right bank as viewed from the rear of the engine. The other bank has a very strong spark that jumps a 1/2" gap no problem. Any ideas ? I have a home made dva adapter and will try to collect some data after work today.

 

[oldboat1]

Try switching a coil/coils. The power pack can be had, but not real cheap.

Actually, before switching coils, check grounds and connections.

[ed. '73-'77, but may resemble yours: https://maxrules.com/graphics/omc/wiring/V4_1973.jpg ]

 

[boobie]

I'll go for the power pack. JMHO ..

 

[Chevyls6]

Ok I didn't have a lot of time to troubleshoot it tonight but I have some results.

Stator is putting out 217v resistance is 767 ohms

​​​​​​Both timer base sensors are at 7.5 ohm. The 1-3 sensor puts out .6v when connected but the 2-4 sensor puts out almost nothing while connected but jumps to .7v when disconnected.

Does this sound like a power pack failure ?

When I first started testing I got one strong spark out of the right side bank and then nothing.

 

[Chevyls6]

Update: I charged the test battery and now I've got spark on all cylinders. Still seems kinda flakey tho like it doesn't produce a spark on every compression stroke.

 

[oldboat1]

:facepalm:

 

[Chevyls6]

Ok I figured it out. The terminals on the ends of the coil wires aren't making good contact with the spark tester. Guess I'm gonna change those out. Cleaning the grounds also did help. Some looked ok and others were a little corroded.

 

[oldboat1]

frustrating, ain't it. Glad you have it figured out. Don't know if you tried the motor yet, but keep posting. (Success stories welcome too.)

 

[Chevyls6]

I tried to fire it tonight but just couldn't get it to catch. Taking the carbs apart and doing a basic cleaning seemed to help but not quite enough to get it going.

If I look through the venturis while cranking some of the idle jets are spraying more fuel than others. I'm gonna try deep cleaning and rebuilding both carbs next.

 

[oldboat1]

Might use the manual choke when you try starting again. Hearing the solenoid doesn't necessarily mean the choke plate is closing.

 

[Chevyls6]

Might use the manual choke when you try starting again. Hearing the solenoid doesn't necessarily mean the choke plate is closing.

Good point, but I was using the manual choke. I could see loads of fuel coming out after choking it but it wouldn't fire with or without the throttle open.

I've got carb kits and new plugs on the way. The plugs were absolutely caked with carbon when I first looked at them so I'm hoping it's just losing spark through those deposits.

When the carbs were off I checked the Reed plates with my finger to see if they were stuck and all of them opened.

 

[Chevyls6]

Update: I managed to get it running with a new set of plugs and some dielectric grease on the plug wires. It fired and sounded pretty good on just the fuel left in the carb bowls from my first test.

Several plugs had high resistance and one maxed out my 20 M ohm meter.

Seems like this is gonna be a pretty good motor.