1981 E70ELCIH - sounds rough, weak/hollow, and vibrates/jolts

[mobisware]

1981 Evinrude 70 hp motor, 3 cylinder. Motor was stalling, running rough, vibrating, jolts, and sounds weak/hollow. Used spark tester to confirm all 3 coils are sending electricity to the plugs. Replaced plugs and plug wires. Made adjustments to carb and idle stop screw. Also switched to fresh tank of fuel, then recorded this video. As you can see/hear, it no longer stalls at idle but still sounds rough, weak/hollow, and vibrates/jolts.

 

[flyingscott]

The motor in the video is a yamaha not the same. Sounds like a misfire or plugged carb. Do a compression and spark test

 

[mobisware]

Compression is about 120 on all 3 cylinders, spark tester flashes on each coil. The cowlin says Yamaha but the contents are Evinrude. All 3 carbs were cleaned in August (using 1981 E70ELCIH Evinrude Parts). I'll check the carbs. Is there anything in particular I should be looking for? Or a specific test I should run?

 

[emdsapmgr]

If the small idle passages get any dried fuel in them, that will restrict the flow of fuel at idle. An occasional miss at dead idle. Not an ignition problem, but a lean condition called a "lean sneeze." The carbs must be torn down to fix. If this is the problem, you will need some aerosol cleaner, like a GUMOUT type product in order to dissolve any dried fuel in the inside of the carbs. A fuel additive won't work.