OMC King Cobra Running rough

[rphissong]

I have a 1996 Chris Craft 25 Crowne with the 7.4 L OMC King Cobra. This is the GL 300 hp engine, with the EEM ignition. Saturday, while driving on the lake, it started missing very badly, and even stalled a few times. It would clear up, and run bad, then clear up etc. I got it back to the launch, and pulled it out for the season. I should also mention that once in a while when adjusting the power trim at cruising speed, this would cause the engine to start cutting out too. As soon as I let off the trim / tilt button,the miss would go away. It was like this was causing a grounding issue in the ignition system. I have heard these king cobra EEM ignitions are trouble. Has anyone run into this before, or have any suggestions?

 

[bigdirty]

Re: OMC King Cobra Running rough

... I should also mention that once in a while when adjusting the power trim at cruising speed, this would cause the engine to start cutting out too. As soon as I let off the trim / tilt button,the miss would go away. It was like this was causing a grounding issue in the ignition system. I have heard these king cobra EEM ignitions are trouble. Has anyone run into this before, or have any suggestions?

I dont know too much about the EEM ignition, but it sure sounds like you have a grounding problem either with the boat trim/wiring or the ignition system. i chased a problem like this for 3 days in my old formula, turned out to be one bad wire from the motor harness up to the switch/gauge panel. If a circuit looses its ground, it will find the next easiest one, and usually that plays havoc with everything around it. (i literally had the wipers come on when i hit the horn button, cranked the motor and fuel guage would go up..:laugh: ) Another thought, was your volt meter well above 12V while running? (like 13-14v) If the alternator is giving up and not charging well, (possible voltage reg shot) id think the ignition system would be using a lot of the available juice, then you hit the trim/tilt and it drags the power down, causing the motor to cut out. Is that an efi motor? I know most ecu's generaly don't like voltage fluctuations or drops, they get confused..

 

[rphissong]

Re: OMC King Cobra Running rough

Yes, the voltmeter was around 14V. The fuel gauge does act kind of goofy though, like will read steady, then jump to dead empty, then back to normal. It an ECU controlled, carburated motor. I see some posts out here about these King Cobras. I think I will go through the wiring and verify every connection is clean and tight, then install a Delco marine distributor. These are available for around $300.

 

[Tnstratofam]

Re: OMC King Cobra Running rough

We had a similar problem with our Stratos. It has the 350 king cobra and sometimes when I would adjust the trim it would cause the motor to stumble like it was loosing fire at the distributor. Ours has been converted to electronic ignition already. A local mechanic told me there is a wire that runs from the alternator to the eem that is purple and pink. He advised me to cut exactly 21 inches out of the wire, because of a resistance problem. I've not done this yet as I am in the process of doing a restore on her. I would check all your electrical connections first and then see how it goes. I'm not real sure about the whole cutting into my wiring idea, but if I still have trouble after my resto I may try it. I'll be keeping tabs just incase you get it figured out. I'll post a reply here if I find out anymore. I'm sure others have a better idea on what to do.

 

[HT32BSX115]

Re: OMC King Cobra Running rough

Yes, the voltmeter was around 14V. The fuel gauge does act kind of goofy though, like will read steady, then jump to dead empty, then back to normal. It an ECU controlled, carburated motor. I see some posts out here about these King Cobras. I think I will go through the wiring and verify every connection is clean and tight, then install a Delco marine distributor. These are available for around $300.

Getting rid of that "OMC/volvo" electronic ignition will probably save you a lot of grief over time.
(the older OMC Spit-Fire ignition is completely unsupportable now)

Make absolutely sure you actually DO have an overheat though.

The "jumping" fuel gage should be your clue that you have some rather easy to fix electrical problems ot simply a bad gage/sender.......

 

[jerryjerry05]

Re: OMC King Cobra Running rough

Running and missing, then clearing up.
Could be there is water in the gas.
Check the water/fuel sep.filter.
Had that problem with a 350 King Cobra and it was a pinched wire.
The bell housing ended up with a wire pinched between it and the block.
Prior engine work and when it was reinstalled it must have slipped in there?

 

[duckstar]

Re: OMC King Cobra Running rough

Got a similar problem,5.8 runs smooth at the dock, as soon as i put it in gear she starts to get rough and die out on me, also trim guage is jumping all over the place,any help would be appreciated, thanks!

 

[HT32BSX115]

Re: OMC King Cobra Running rough

Got a similar problem,5.8 runs smooth at the dock, as soon as i put it in gear she starts to get rough and die out on me, also trim guage is jumping all over the place,any help would be appreciated, thanks!

Howdy,


It's really better if you start your own thread instead of tagging on to a current thread.

 

[jerryjerry05]

Re: OMC King Cobra Running rough

Sounds like ESA's kicking in.

 

[HT32BSX115]

Re: OMC King Cobra Running rough

Sounds like ESA's kicking in.

That's a cone-clutch VP drive. I don't think it has an ESA like "Dogs" had.

 

[bruceb58]

Re: OMC King Cobra Running rough

That EEM ignition system was only used for a few years on 7.4L OMC/Volvo partnership years. I know because I have one. I actually just purchased a new Delco EST to replace it.

There is no ESA.

Sounds like the OP has a voltage drop problem which is accentuated by using the tilt/trim switch.

 

[duckstar]

Re: OMC King Cobra Running rough

That EEM ignition system was only used for a few years on 7.4L OMC/Volvo partnership years. I know because I have one. I actually just purchased a new Delco EST to replace it.

There is no ESA.

Sounds like the OP has a voltage drop problem which is accentuated by using the tilt/trim switch.

what is the op ,trim guage is jumping all over the place,sorry Im not a mechanic just lookin for some answers! thanks

 

[bruceb58]

Re: OMC King Cobra Running rough

what is the op ,trim guage is jumping all over the place,sorry Im not a mechanic just lookin for some answers! thanks

OP is original poster. You need to become an OP by starting your own thread.

 

[Lou C]

Re: OMC King Cobra Running rough

I had this and another oddball problem (getting a shock when trimming while holding both the shift lever (metal) and the metal steering wheel.
First one (stumble when trimming) was cured by replacing all the battery cables and making sure the connections at the trim relays were clean and tight. I also cleaned the ground studs on the engine block. That took care of the stumble while trimming. That trim pump draws a LOT of current and it can drop the voltage down low enough that the ignition system starts to get wacky.
The second problem (shock while trimming) was cured by taking off the trim piece on the shifter handle and sealing up a bare spot in one of the wires.

 

[jerryjerry05]

Re: OMC King Cobra Running rough

Duckstar didn't list the motor/year or any serial #s The KIng Cobra could have been ANY of the 5.8s they put out in the 80's
They used the KIng Cobra stickers on a lot of the Cobras even a 2.3.
Unless you knew what he had?? I posted what it might be.

 

[bruceb58]

Re: OMC King Cobra Running rough

Duckstar didn't list the motor/year or any serial #s The KIng Cobra could have been ANY of the 5.8s they put out in the 80's
They used the KIng Cobra stickers on a lot of the Cobras even a 2.3.
Unless you knew what he had?? I posted what it might be.

This is the reason Duckstar needs to start his own thread. Too confusing when second people start posting.