1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

[mike11374]

I have a 1991 Caravelle that seems to keep running after shutoff. Usually lasts 10 seconds up to a minute. Any idea what this might be and is it serious?

 

[tommays]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

its bad because during the sputtering the motor can run backwards and draw in water and hydrolock<br /><br />many causes wrong tuneup settings or parts<br /><br />high idle <br /><br />high engine comparment temp(run blower)<br /><br />shut down to soon after long run(let idle for a few minutes to cool down<br /><br />tommays

 

[mike11374]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

what do you mean when you say hydrolock?

 

[rbezdon]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

the engine can kick a bit and sometimes it causes a slight rotation of the crank in the wrong direction. This causes a suction on the exhaust side sucking water into the engine through the ezhaust which is in the water. Once water is sucked in and he valve closes, the water is a liquid and liquids can not be compressed. The piston comes up the cylinded and tries to compress the water but it cant locking the piston from coming up any further and locking the engine. This is a prticularly bad condition and can lead to a permanently seized engine if not relieved/remedied fairly quickly. It can aslo lead to ruined fly wheels and starters, some times even starters have broken off their mounting creating expensive repairs. As Tommays says, fix the problem to avoid getting in this condition. <br /><br />A well tuned and properly set up engine shouldn't do this.

 

[mike11374]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

thanks....got any advice on my neutral button post below??

 

[whywhyzed]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

I've been told incorrect timing, or wrong heat range spark plugs can also cause "run on", or even carbon build up on the plugs which may be related to wrong heat range ..(?)...

 

[rbezdon]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

Mike, that is specific to the control you have and likely came with the boat and not the engine/drive combo. I have no clue as the one you have must be quite different from mine. I have no button. I slide the whole throttle lever out from the mounting and then I am in neatral where I can use the throttle lever and stay in neutral. It sounds like a mechanical issue with the switch or wiring to the control itself, not with the engine/drive.

 

[sea wolf]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

What octane fuel are u running? On my Cobra if I run 87 it will run on. I now use strictly 89 & it never runs on. Switch to a higher octane if you're using 87 & see if that helps. It's also stamped on my flame arrestor to run 89 octane.

 

[trebor0301]

Re: 1991 OMC Cobra---keeps running (sputtering) roughly after shutoff

Hey Mike,I had the same problem as you.My boat ran great up until the time I started using the gas at the marina.I thought maybe carberater troubles or even timing was off.Then one day I brought gas in from the gas station(the marina would be closed)and the problem was gone.I have since gotten gas from both places to test my theory and have decided it was the octane.the marina sells only the low grade.I bring in at the very least mid grade.Give it a try before you get all crazy with carb adjustments.