Re: evinrude 40hp, unusual engine problem
If the engine is shutting off like you turned the key off, your most likely culprit is a wire that has worn through and is shorting out. Inspect any wires running to/from the ignition plate. If you have a UFI ignition system, you'll have to remove the flywheel to check things out. But, before you start disassembling things on the engine, make sure the throttle linkage at the control box isn't shorting out any wires for the key switch.<br /><br />You said "if you place the engine in neutral and and andvance the engine to 4,000 rpm the engine will then advance on it's own until you shut the engine down." Yes, under no-load cirvcumstances they will do that. It's called "engine run-away" and under no circumstances should you ever rev a 2-stroke engine above a high idle (say, 1500 rpm's) when in nuetral, it can cause serious damage to the engine.<br /><br />You also said "if you remove the engine cover and while the boat is running in neutral anvance the carb linkage by hand to 4,000 rpm the engine will not advance on it's own." That's because when you advance the carb linkage, you're not advancing the engine's ignition timing. The advanced ignition timing is the driving factor in the engine run-away situation you experienced.<br /><br />With no-load on the engine, the rpm's are able to spin up quicker (sooner) in relation to mechanical timing advance, that's most likely why the engine doesn't shut off when you rev it up in nuetral. Most likely, if you kept advancing the throttle, you would "bump" that worn wire and shut the engine off.<br /><br />Hope this info helps.<br /><br />-John