Re: 1974 Evinrude 9.9 won’t idle at low RPMs, need help

[Don]

Glad you got the 74 working correctly, that carb mixing pocket surely was a mess! Did you ever find/remove the pesky needle valve seal? That crusty mixing pocket sure looked like the problem area though…..
The 1981 Evinrude in your other video is surely a keeper! Looks like a low hour fresh water engine. OMC had perfected these engines by 1981. The only real issues for the 81 models were a misdesigned upper water tube grommet that creates expensive cooling headaches along with the usual throttle control headaches.
Hard to tell just what is going on with the 81, sounds lean, but he didn’t really feather the choke much to confirm/deny a lean condition. Did he try enrichening the mixture a bit? Could be a fuel supply issue/fuel pump/air leak, the fuel tank is way below the engine while running in that tank which can really tax a marginal fuel pump, inlet air leaks/restrictions. He might try having an assistant pump the fuel bulb while the engine is running to help evaluate fuel deliverly problems. Again, please do NOT disassemble that fuel pump, except to remove the plastic inlet cover to check the mesh filter. These engines can be a little cold blooded, don’t expect it to idle real well until it has had a chance to warm up a bit.
Again, start with the basics, compression/spark/fuel. Is the fuel/oil supply fresh? Is this engine new to you guys, do you know any of the service history? When was the last time it ran OK?