OMC Cobra 5.0 intermittently bogging down

[vv1500]

Hi I am having trouble with my omc 5.0 cobra. The boat has been running fine but just recently it has been acting up. With the throttle wide open it acts as though something is holding it back. It acts like it wants to go but then bogs down and won?t go over 2k RPMs. Earlier today it was doing this and then backfired and then ran fine for the rest of that trip. My wife said it sounded like it just needed to burp. It seems to run fine in neutral. I thought maybe that I got some bad gas or that the carb intact was clogged so I ran some intact cleaner through it and a bottle of dry gas. After that it seemed to run ok for about 5 minutes and then the problem came back.

The problem is really hard to describe but any help would be greatly appreciated.

Thanks

 

[bruceb58]

Re: OMC Cobra 5.0 intermittently bogging down

How old is the gas?

Have you replaced all the fuel filters?

When was the last time you did a full tune up?

Check the timing to make sure you get full advance at max RPM.

It is possible that you may need to get your carb rebuilt.

 

[vv1500]

Re: OMC Cobra 5.0 intermittently bogging down

Thanks for the info.

The gas is only a few weeks old although I did run some dry gas and intact cleaner through it just to make sure.

I changed the fuel filter and sprayed the carb with gumout today. That seemed to have helped. The boat ran better the rest of the day. I have new plugs but could only remove a couple of them because my spark plug wrench didn't fit. The 2 plugs I removed looked to be in decent shape.

I pretty sure though the engine is still not reaching it's full potential. I am only getting up to about 3400 - 3600 rpms.

 

[vv1500]

Re: OMC Cobra 5.0 intermittently bogging down

Ok so today I was out on the water and the boat ran fine for a little while but then started having the same bogging problem again. I tried the gumout in the carb trick again and that didn't work this time. I am planning to rebuild the carb the next time I can get up here. What info do I need to buy the proper rebuild kit?

Thanks again.

 

[dhondarider]

Re: OMC Cobra 5.0 intermittently bogging down

my 5.7 is doing exactly the same thing as this. did you fig it out. i know its been a while

 

[SpartyOn]

Re: OMC Cobra 5.0 intermittently bogging down

my 5.7 is doing exactly the same thing as this. did you fig it out. i know its been a while

I have a 1995 5.0 omc doing the same thing. I had a new carb put on it by a marina. It ran for a a few times out only to start acting up again. If anyone can help please do so. Thanks

 

[BB180DAVE]

Re: OMC Cobra 5.0 intermittently bogging down

I've always thought I was a good DIY person. This one has stumped me also. My 5.0 has acted the same way 2 yrs. Runs fine for a short while then boggs down. Idle is ok. Thought it was the carb, replaced it later rebuilt it, replaced fuel filter. This year had new wires, plugs, module ($150 part), coil, distr cap, rotor, eval run on dyno-test by mechanic 7/30, all checking out. Yesterday July 31, my first day out this season! Engine purrrrrs, runs great through all rpm ranges and loads. Took a nice long ride. About 45 min. in Deja-vu. Had to pump throttle to get on plane and keep above 3000 rpm to keep it from stalling. Looking for some genius out there.

 

[drrm123]

Re: OMC Cobra 5.0 intermittently bogging down

I'd try cleaning electrical wires connectors with scuff pad. starting at the starter solenoid, coil battery and under the dash. check fuse contacts also. remove clean and reinstall making sure you have good connection. check to see if any wires feel hotter than normal after running engine. after that the next option would be to check compression and general condition of engine if you didnt find electrical wiring trouble. Next check valve adjustment.

 

[Rocky_Road]

Re: OMC Cobra 5.0 intermittently bogging down

I've always thought I was a good DIY person. This one has stumped me also. My 5.0 has acted the same way 2 yrs. Runs fine for a short while then boggs down. Idle is ok. Thought it was the carb, replaced it later rebuilt it, replaced fuel filter. This year had new wires, plugs, module ($150 part), coil, distr cap, rotor, eval run on dyno-test by mechanic 7/30, all checking out. Yesterday July 31, my first day out this season! Engine purrrrrs, runs great through all rpm ranges and loads. Took a nice long ride. About 45 min. in Deja-vu. Had to pump throttle to get on plane and keep above 3000 rpm to keep it from stalling. Looking for some genius out there.

I would make sure that your gas tank vent is not plugged (wasps in my neck of the woods, love to build their nest in the vent outlet). A clogged vent will run fine initially...until your tank has created an unwanted vacuum. Easy way to see if your tank vent is the culprit, is to loosen (crack) your gas cap...and do a test run!

 

[BB180DAVE]

Re: OMC Cobra 5.0 intermittently bogging down

Thanks for the suggestions gentlemen. Today we have rain at Mississippi R. MM224. I'll persue Tomorrow.