Really wierd issue, Johnson '84

[maggun]

Johnson 50 '84, Mod. nr. J50BELCRM<br /><br />We have had some earlier issues with the ignition, spark was bad on cyl nr 1, which was fixed after replacing the power pack.<br /><br />What is left is an engine that still runs rough on idle, it revs up, and occasionally drops down almost to a stop. When it does this, it sounds like its misfiring, with a puff sort of sound. I have used a stroboscope to view as the engine does this, and dont think it's related to the ignition.<br /><br />While we was testing the engine, we had a incident where the engine revs up like usual, but this time it went up to at least 6000 rpms, even though the help throttle was put to the bottom. Even turning off the ignition key didnt help, it was still running madly! That took me by surprise, and had me try to remove the spark plug caps to no help. Eventually managed to kill it using the manual lever on the electric choke to suffocate it.<br /><br />Removing the spark lead to nr 2 indicates that nr 1 is the one running rough and badly, as it stops easily, nr 2 alone runs ok.<br /><br />I have done a compression check several times earlier, and it looks good, but someone told me one can easily be fooled by this test. So I dont know how much I should value this positive check.<br /><br />I have also gone over the fuel delivery, and cleaned the carbs, replaced inlet valve, synch procedure etc.<br /><br />I have no idea as to what can cause this, anyone have an idea?

 

[ezeke]

Re: Really wierd issue, Johnson '84

The runaway is dieseling which can happen when you run a motor with no load, which is why you don't want to run an outboard on ears above an idle. The motor keeps pulling in gas and exploding it by compression alone. <br /><br />While timing may be be an issue, I think you may still have fuel problems. Is the gasoline fresh?<br /><br />You will want to make sure you have torqued the flywheel to specifications after you check to see if the key is intact.

 

[maggun]

Re: Really wierd issue, Johnson '84

Originally posted by ezeke:<br /> The runaway is dieseling which can happen when you run a motor with no load, which is why you don't want to run an outboard on ears above an idle. The motor keeps pulling in gas and exploding it by compression alone. <br /><br />While timing may be be an issue, I think you may still have fuel problems. Is the gasoline fresh?<br /><br />You will want to make sure you have torqued the flywheel to specifications after you check to see if the key is intact.

We haven't had the flywheel off.<br /><br />The gasoline is the same as we use for another johnson engine, and it works fine. It is also refilled and hence renewed occasionally as we use it.<br /><br />The thing is that we only run it in idle, but the engine keeps dropping up and down. And even putting the help throttle to the bottom didn't help before it went dieseling. Sometimes have to give a bit throttle to stop it from dying.<br /><br />I am not completely sure what you mean by "check to see if the key is intact. "?