runaway 48

[DOGHUNTER]

I have heard of a motor running away but I have witnessed it myself.my 48 johnson spl began to run at about 3500 rpm's without the secondary coil leads connected to the spark plugs.It began to run at a very high speed in neutral and I suddenly removed the secondary lead wires and it kept on running for a while until it ran out of fuel(I disconnected the fuel line).At this time I suspect the ignition module has failed.On my motor the ignition module is located under the flywheel and it contains the sensor coils and the SLOW circuit.Sometimes it runs at full throttle and other times it runs at half speed.I checked the reeds the carbs. and all were ok Could I be on the right track

 

[12Footer]

Re: runaway 48

It is caused by heat in the combustion chamber. It happened to me about 2 months back, spooked me bad. Freaked me right out! I never whitnessed it before.<br />What happened to me was a long day on the river, idling here, and idling there. Carbon built-up in the jugs. When I was back at the house on the muffs, flushing the engine (which I do imediately after I back her in), Started the engine,and went about stowing the gear in the garage.<br />All of a sudden, the engine revved-up to full-throttle. I cut the ignition switch,and nothing happened! I threw it inot gear,and nothing changed. I ripped the muffs off, and gave it a drink of water..That did the trick.<br />I came on this great site, and asked everyone else if they had ever seen experianced this..<br />Some had,and explained what it was.The glowing carbon was acting like a spark plug, and the carb was sucking fuel as it needed it, to stay running. It ran-away like a diesel with no governor on it.

 

[DJ]

Re: runaway 48

Carbon build up, it's time for a serious decarb. Search this board for the procedure.

 

[StAugVol]

Re: runaway 48

I don't expect anyone to see this since it's such an old post, but what about a runaway when the motor is cold? I just put some Yammie Ring Free in this tank, which is fresh 87 and oil, 50:1.<br /><br />My JohnnyRude 115 SPL takes off like a rocket after I put a water pump in. Have no clue...

 

[12Footer]

Re: runaway 48

Hi, Dave. I would say your problem is still carbon buildup.<br />Ringfree and other decarb treatments can only help prevent it, but it cannot stop it. If the ignition cannot shut you down, the problem is something embering in the combustion chamber, and that usually means carbon getting hot enough to ignite. when this happens, it detonates the fuel it has,draws more in as the engine ramps-up,draw more fuel in,until it's maxed out.....Like a diesel.

 

[StAugVol]

Re: runaway 48

Thanks 12ft<br /><br />How to remedy and rule out the carbon buildup issue?