Problems with 5.0 L OMC cobra

[agibson]

I just bought a 1993 Glasstream with a 5.0 L, 2 brl OMC cobra. The boat starts fine, runs smooth and revs nicely. As soon as it gets to operating temprature it begins to miss and back fire and finally stalls out. I have checked all connections changed the fuel filter, checked the distributer cap. If I let the engine set over night, it starts up and runs great again until it gets warm. The previous owner just had the ingition module in the distribitor replaced and the coil. Can anyone help me out ????

 

[Bondo]

Re: Problems with 5.0 L OMC cobra

Ayuh,....

When it Quits,........

Check it to see if it's Lacking Fuel,.... Or Fire.........

 

[agibson]

Re: Problems with 5.0 L OMC cobra

When I exercise the thottle it is spraying fuel into the carb

 

[Bondo]

Re: Problems with 5.0 L OMC cobra

Ayuh,... OK....

Then grab your multimeter,+ See Where the power Stops.......

 

[whywhyzed]

Re: Problems with 5.0 L OMC cobra

....

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Mine is electronic Ignition, it does not use a coil with the resistor

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Well same thing today, went out this morning. Boat started right up, ran very nice temp got to 160 ran for about another 5-7 minutes then started missing and finely just stalled out. If I try to restart it it gets worse and worse. If I wait several hours it will start and run great, then do the same thing again.

 

[Haut Medoc]

Re: Problems with 5.0 L OMC cobra

Heat sink to the ignition module?.....
You need to get the multi meter & find where you are losing electrical power when the situation occurs.....
One other possibility is water in cylinders.......
When were the mans/risers changed last?....
Pull some plugs & spin the engine when this occurs......
Sitting for awhile will allow water to seep past the rings.....
How is the condition of the oil/oil level?.....​

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Not sure about heat sink on the module in the distributer, I didn't install it. You may have a point about the manifolds and risers though, I do notice a bit of white smoke after she starts and seems to get worse the longer it runs, could the water be backing up and going into the exhaust valves and trying to burn until there is just to much to burn ? The oil looks fine no milky look at all.

Thanks

 

[JustJason]

Re: Problems with 5.0 L OMC cobra

run it and shut it off... give it a few days then pull the plugs... are they rusty?
Where are you located and what is your outside temprature... could this simply be vapor lock?
When you say backfire... is it popping through the carb or out of the drive?

It's an omc.... sell it and don't look back.

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Well you are probally right, I have always had Mercuisers, but bought this because my wife wanted a bowrider and I wanted at V-8, went ot start it this evening and would not turn over, so charging batterys and will see what she does in AM

Thanks to all of you for you responses. have not found out problem yet, but sure I will,,, all you guys offer a great service, with boat repair at $110.00 a hour here, who can even afford to own a boat anymore

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Still have not found the problem, checked the Ingintion system with meter dissasembled the carb and both looked fine, removed the risers and also found no problem

 

[THE BEEF]

Re: Problems with 5.0 L OMC cobra

What kind of float is used on the carb? Brass or plastic.
Plastic ones can saturate and cause flooding. When it starts cutting out is there a lot of black smoke or a strong smell of unburnt gas?
Beef

 

[whywhyzed]

Re: Problems with 5.0 L OMC cobra

....

 

[agibson]

Re: Problems with 5.0 L OMC cobra

No there is no gas smell, a small amout of white smoke when it starts to miss. Seems to be getting fuel just fine, took carb apart yesterday and inspected the inside, every thing looked fine. Started right up afterwards and ran for 10 minutes then started to miss again and finally stalled out.

 

[jfcar]

Re: Problems with 5.0 L OMC cobra

Do a compression check on motor, could be bad head gasket.

 

[mcleaves]

Re: Problems with 5.0 L OMC cobra

Steam out the exhaust and getting worse the longer he runs seems like a smoking gun to me..

I also had the heat sink problem on the ignition module on my old '84 Nissan Maxima. Took FOREVER to track down. As long as th module was cool it was fine. After a long run or on a warmer day it would miss and stall. let her sit and start back up.

But I'd be looking into that steam first. The modules rarely go.

M

 

[a70eliminator]

Re: Problems with 5.0 L OMC cobra

Hmmm.. lets see, she warms up to say 160, at this the point the T-stat is open and water is flowing through the heads then it spits and sputters and evetually quits, i'm not going to say it.

 

[agibson]

Re: Problems with 5.0 L OMC cobra

Well found a bunch of wires under the dash melted together, redid them. The wires were the grounds on the tach melted to other wires. I am almost convinced that it may have damaged the ignition module. Even when the boat gets cooler ( I started it today temp at 120 and still did it after 5 min.) If I wait several hours it will start and run fine for about 20 minutes. If I try to start it again right away it gets worse. All ready swapped out the coil so I ruled that out. This module was replaced just before I bought the boat and the old owner took it for a quick ride and it was fine, when I looked at it to buy it, it ran fine. This started the day after I bought it.

 

[a70eliminator]

Re: Problems with 5.0 L OMC cobra

Well found a bunch of wires under the dash melted together, redid them. The wires were the grounds on the tach melted to other wires. I am almost convinced that it may have damaged the ignition module. Even when the boat gets cooler ( I started it today temp at 120 and still did it after 5 min.) If I wait several hours it will start and run fine for about 20 minutes. If I try to start it again right away it gets worse. All ready swapped out the coil so I ruled that out. This module was replaced just before I bought the boat and the old owner took it for a quick ride and it was fine, when I looked at it to buy it, it ran fine. This started the day after I bought it.

Key word "Quick"
Ok Ok I'll say it "head gasket"