3.0 OMC stalls after it runs for a while

[m48strat]

Problem: After my 3.0 OMC runs for a while it stalls out. At first we thought it was a coil problem. So, I took a spare coil and replaced it when it stalled, and still wouldn't start. We replaced the fuel pump amd this seemed to solve the problem. We had the boat out twice after this fix. the first time we ran for about an hour and no problem. The second time we took it out, I was out for over three hours, had no problems. The next day we took her out and she ran fine for about an hour, as we were headed back to the dock at about 3500 rpm she stalls. We got her started again and limped back to the dock. When I got her home, I put on the muffs I couldn't get her to start and idle unless I had the rpms over 3500. At low idle she she starts missing and choking and then stalls

 

[marunr]

Re: 3.0 OMC stalls after it runs for a while

Is your shift interrupt switch working correctly? It should be riding in the center of the V shape, not on top. On mine, if the overstoke switch engages you can still run the boat but it won't stay running because it isn't designed to work that way...hence it may stall after a time. If it is out of adjustment you will need to read this.<br /> http://www.funkopolis.com:8080/~stuart/cobra/

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Yes, the switch was in the center of the V on the cam. The last time I tried to start the engine, the switch was in the middle of the actuator and I tried making the switch to make sure it wasn't stuck. The engine now starts, but while idleing in low rpms it acts like it's missing and wants to stall. When I give it more gas it, around 3500 rpm, it smoothes out

 

[Boatist]

Re: 3.0 OMC stalls after it runs for a while

Sounds like a spark problem to me. I would check the points and make sure they are clean and gap is about .019. Dwell should be 31 to 34 degrees. When it is failing put a timing light on and check timing for number one but also make sure getting spark on the other 3 wires. If the dwell is off then clean and adjust points. Still off change points and condenser and adjust again. If no spark on one or more cylinders then check rotor and cap. Make sure have 9 to 10 volts on the plus side of the coil.<br /><br />Could also be water in the fuel or choke problem.<br /><br />Check compression to see if have a stuck lifter or head gasket.

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Thanks Boatist, but, points, rotor, cap, and plugs are all new, put in at beginning of season. What's making this so frustrating, is, the problem is so intermittent. When the boat runs, it runs great, then all of a sudden it will start acting up. The carburator was apart and adjusted also, but I'm beginning to think that's where the problem may be

 

[lowshovel1]

Re: 3.0 OMC stalls after it runs for a while

sounds like the float is sticking and flooding on ya.----assuming it's carb?

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

thanks for the imput lowshovel1. Going to check the carb this afternoon when I get done work. I hate it when work gets in the way of working on my boat. Assuming it is the float, would the remedy be to rebuild the carb? And would a sticking float cause it to stall at low rpms?

 

[marunr]

Re: 3.0 OMC stalls after it runs for a while

If the float level is too high it will flood out during idle. You can probably see the gas flooding in to the throat of the carb. Is there a lot of black smoke? <br /><br />Last year I had a similar problem and it turned out to be a faulty condenser. I never considered it since it was new. After a tune-up, the boat ran great for a few days and then I encountered the problem...a terrible miss at idle which would smooth out at higher rpm. (Actually it didn't, it just sounded smoother.) Do you still have your old points and condenser? I had thrown mine away, but from now on I'm saving them until I know everything is ok.

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Interesting marunr, nobody has suggested the condensor. Is there any way of checking the condesor short of replacing it. A mechanic friend of mine and I are going to work on it this afternoon. i'll let you know if we find anything

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Update: Last night we checked all the ignition parts. Everythings checked out alright. We're getting plenty of spark, so we ruled out the condensor. Next we checked the carbuator, it seemed to be dumping fuel, so we pulled it and sent it out to be rebuilt. May take a day or two to get it back.

 

[bigdaddyofhouse]

Re: 3.0 OMC stalls after it runs for a while

It sounds to me like you have some trash in your fuel line.<br /> You said that it ran fine after replacing the fuel pump, but after a few hours running it started ---king up again. I would try blowing back on the fuel lines (from the pump) with pump removed, and see what happens.

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Thanks bigdaddy, at this point I'm trying all suggestions. What's really a *****, it only acts up when I'm out on the water.

 

[Aquadzac Captain]

Re: 3.0 OMC stalls after it runs for a while

If you are out in the water and it runs great for a bit then you idle down to troll speed and the motor begins to stall or hard start you may have "VAPOR LOCK". This is when the fuel lines get too hot and the fuel reaches boiling point and vapors into the carb rather then inject gas wet. Thus the motor dies or hard to start at idle. That is until it cools down and then the cycle starts all over. Very rare but can happen. My exposed rubber fuel lines are soo close to the manifold, inline fuel filter touches water hoses, that they are getting a brunt of some heat. Not to mention heat goes into the mechanical fuel pump and filter from the block adding to the fuel heat increase. Right now I am doing a bunch of temp tests before and after a run to see how hot the dog house is and how hot the fuel lines are becoming before and after a run. Next I plan to move all my lines, go elec pump and take the lines away from the motor and have them protected with braid. Its a plan but yet I dont know if it will fix my problem but I have checked every thing and by looking at the design it could be the culprit. Oh one more thing, I have no scoop to push air into my lower dog house (motor housing) thus the ventelation in my motor well is getting way hot. I shoul have been using my blower all along. More to come on one of my posts soon.

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Thanks for the info aqua, that's something I'll have to look into. Right now I'm waiting for the carb to be rebuilt. Should be done today. I'll post the results after we get it installed and test her out.

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Update: We just put the carburator back on and it started up and ran fine through a range of rpms. The mechanic who rebuilt it for me said he did find some gunk in the carb. the real test will come this weekend when we put in the water and put some hours on it. Thanks to all who replied to my post. For a newbee boater like myself, this has been a real learning experience, and I appreciate the help and advice I've gotten from this forum.

 

[Aquadzac Captain]

Re: 3.0 OMC stalls after it runs for a while

Vapor Lock review: Inboard houseing closed now blower got only up to 108 degrees F in 92 degree heat. L pipe aluminum going into my Eldebrock that is attached to a rubber fuel line AREA got up to 131.5 degrees F. The question is that enough to Vapor Lock fuel ??

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Update: took boat out this weekend and she ran fine. Seems we found the problems. Combination, fuel pump and carburator.

 

[EstelleRob]

Re: 3.0 OMC stalls after it runs for a while

We have a 1989 Fourwinns with an OMC 3.0L Cobra inboard motor. The boat ran great last year without any problems. Now when it runs for about 3 to 4 hours it just acts up an stalls. We cannot get it started again. The mechanic has replaced the fuel pump, filter and water pump, we took it out yesterday and it stalled again after about 3 1/2 hours. The mechanic replaced the fuel pump twice but the problem is still not fixed. Any suggestions??

 

[m48strat]

Re: 3.0 OMC stalls after it runs for a while

Your problem sounds a lot like mine. As it turned out my problem was a combination fuel pump and caberator. Sice the carb was rebuilt, the boat runs fine.