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I also had a Heart attach ! Engine Keep running EVEN if I unplug all spark plugs

M

Mz3bo

New member
Hello Folks,

Title should read 'had' a heart attack...

So I came back from a very scary experience. I am fine tuning my carb and timing on my 85 V4 1979 Johnson. So far, it is idling roughly after my carb rebuild and I was in the process of doing a link and sync.

So once my rods all properly positioned, I started the engine. It was doing ok-soso... i manually opened 25% of the throttle and pull it back... then it started to rev... to a steady 'id say by the sound 4000rpm'... when I pulled the throttle back, it did not slowed down so I was like.. WTF... retried a few time and nothing (it was sputtering at 4k)... So I jumped to the key turned it off and no more sputtering but the engine was still running, the flywheel spinning like hell (starter is not engaged)... I was starting to freak... I jumped to the back and puller all plugs Wires... stilll running... I disconnected the fuels line and 1 or 2 minutes after the engine died...

Wow... that was a scary thing. Now, I notice it overheated as the buzzer was crying and there is not more water coming from the Peehole except some smoke... I don't remember but I think I was a lot a water coming out of the idling relief valves at some point, but cannot confirm on that as I was running llike a mad man....

Hope someone can chime it...

Thanks
Bo
 
Bo..... Hopefully every reader takes note of your experience.

It has been mentioned time and time again to NEVER open the throttle while in neutral or even in gear if running on a flushette. To increase the rpms beyond 1200 or 1500 rpm is to risk a runaway engine..... a engine that steadily increases its rpm without a limit, and in the process changes its ignition system from a battery supplied automotive ignition setup to a DIESEL one.... as you have discovered.

Usually this ends with connecting rods flying through the sides of the crankcase! This scenario can only be brought to an end (if one thinks fast enough) by jamming your old socks, whatever, into the carburetor throats. Best to have the carburetor face plate assembly removed when working on a engine to have that access available.

As it stands in your case, I can only assume that (from your explanation) that the engine continued to scream away until it overheated and seized to a screeching halt. If so, start cleaning sealing surfaces and installing new gaskets, replacing melted components, and pray that your previous compression returns when you're finished.
 
Hi Joe,

Thanks for responding... I was not on flushette, however, the propeller was not installed in the bucket. I think what happened is pretty much what you described but I was lucky and removed the fuel line fast enought... My question now... What do I need to do to prevent this from the future ? I mean, i cannot stop working on the engine because of that (caus I am really scary as well lol)...

Also, I tried an hours later to restart the engine and it seems like nothing is seize, except and I am not getting any water from the peehole anymore... just smoke...
 
There should be a good steady stream coming out of the water outlet. When you put your hand up, it should be hard enough to feel like a mini garden hose. Good strong stream of water, not smoke. Water pump is easy to replace.
 
FYI

Decarb your engine. Next time if this should happen, Turn off the ignition and go WOT, the glowing carbon on your pistons cannot burn that much fuel and the engine will shut down.
 
Carbon buildup could be due to the motor being over propped. Once you know the motor is running close to 100% check WOT rpms. What is the model number of your motor and how big is your boat?
 
Mz3bo said:
Hi Joe,

Thanks for responding... I was not on flushette, however, the propeller was not installed in the bucket. I think what happened is pretty much what you described but I was lucky and removed the fuel line fast enought... My question now... What do I need to do to prevent this from the future ? I mean, i cannot stop working on the engine because of that (caus I am really scary as well lol)...

Also, I tried an hours later to restart the engine and it seems like nothing is seize, except and I am not getting any water from the peehole anymore... just smoke...
Click to expand...

How to prevent it? Begin by reading what joereeves just said. Runaway is started by over-revving in neutral or no-load condition. Just don't do it!
 
Hi,

Thanks for all the reply. Can you explain why you mention carbon build up ? Is that one of the possible reason or a runaway or a consequence ?

Thanks
Bo
 
That is very likely the issue that occured. When you run the motor especially at high rpms without a load on the prop it takes alot less fuel to run therefore you are running the engine low on oil and the cylinders are burning alot hotter. Same as a four stroke when your running too lean you can burn up valves and pistons. The only thing that cools the pistons is the fuel coming in. If there is alot of carbon on the pistons/heads and plugs it starts glowing from the extreme heat in the cylinders and it keeps snowballing. The best way to do a decarb is on the water as well as your final adjustments. Get a can of seafoam spray and on the water in gear after the engine is fully warmed up spray seafoam in the carbs at high idle speed until it starts smoking real good. Then quickly shut it down and wait 1/2 an hour. Then start it and run it at WOT for about 15 minutes to blow out the cobwebs. Then you can final the slow speed settings. The only thing you should do in a barrel is troubleshoot or flush it is never nesessary to go past high idle speed out of the water and never make adjustments without a load on the prop.
 
Mz3bo said:
Hi,

Thanks for all the reply. Can you explain why you mention carbon build up ? Is that one of the possible reason or a runaway or a consequence ?

Thanks
Bo
Click to expand...

Carbon is a natural by-product of combustion. Think ashes. It is normal and not a problem in the sense that you are thinking. Excessive carbon used to accumulate when we were running car oils and leaded gas, but this is today. Having said all that, yes carbon can accumulate, and the biggest result is sticking piston rings. That is the best reason for de-carbing operations.
 
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