5.7 OMC Cobra 1988..Another Carb Prob..

[rizy1976]

Hi guys, after going through an ordeal I finally managed to get my newly acquired boat to run..\<br />Some history.. got boat.. bad engine bearing.. got replaced... then carb issues, wont idle and very jerky ride on slow speed.. got that fixed by cleaning backfire flame arrester and using SeaFoam..<br />Now the situation is that boat idles very rich stay at around 1500 rpm thus difficulty in engaging from neutral to forward and back.. neutral to backward and back..<br />From my investigation seems like I can not get away without tearing apart the carb... plus ESA might need to be replaced as not reduction in rpm on button pressed...<br />Help.. ideas.. suggestion.... <br />How to get hands on the carb issues.. it seems like a 4bbrl rochester.. they say its a tough one for the beginer? Show I try doing it myself?<br />Would just playing with idleing and putting new ESA might work or atleast worth trying?<br />I've got the saloc manual shows carb job as "Moderate" to "Difficult" difficulty level.<br />Please suggest.. thanks

 

[rojoc]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

NO 1, get the omc service manuals. A MUST! Oline, ebay or other sites. NO 2, if you persist in trying to shift at 1500 rpm you will kill the outdrive! Big bucks! The engine should idle at 600-650. Good luck

 

[rojoc]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

NO 1, get the omc service manuals. A MUST! Oline, ebay or other sites. NO 2, if you persist in trying to shift at 1500 rpm you will kill the outdrive! Big bucks! The engine should idle at 600-650. Good luck

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

rojoc, I do have OMC service manual which looks like a more tech oriented manual. But I have both in hand and also some detailed diagrams and setting document for rochester 4bbrl carb. <br /><br />Now abt the rpm situation. I know rebuilding carb is the best solution but im still hesitant.. looks hard when I look at my carb.. still motivating myself or thinking of finding someone who could do it for me.. <br /><br />What if the guy who worked on the engine stepped up the idleing speed when he was getting facing prob with bad gas in tank and no idleing... Adjusting idle might bring down the rpm to around 800 or so.. Any thoughts on that?

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

Also, I would like to add that Ive tested the rpm on muffs so I guess it would be higher than normal? What is the word for you gurus.. would trying to adjust idle hurt any before tearing apart the carb... <br />Please advise how to adjust the idle on 4bbrl rochester.. <br />Also if I do need to replace ESA whats the cheapest place I could find one?<br />Thanks

 

[bruceb58]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

Originally posted by Rox:<br /> <br />Also if I do need to replace ESA whats the cheapest place I could find one?<br />Thanks

http://www.fasteddiesmarineparts.com/

 

[fendersfender]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

at 1500rpm i doubt that the esa would make a noticeable difference in rpm....esa is designed to work at low rpm's......i think anybody would have problems trying to shift at 1500...as stated before...idle should be set to 650.....I recommend rebuilding carb, or, if your not sure, have it rebiult and start there....after carb is done, set idle mixture and idle speed and see what you have....dont spend the money on an esa module, my opinion is that the idle speed is your problem

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

Scott, would it be a bad idea to first try to adjust idle mixture and idle speed myself before carb rebuild. May be it helps any! What do I have to loose if it didnt work ill try to rebuild carb myself n even if that fails than take the hard hit and pay someone to build it..<br />My guess is that the carb setting was messed up with when engine had problems. Now engine prob is fixed I might be able to get better results by just trying to adjust carb setting back.. Please advise.. <br />You are right about the ESA that might not be bad I realized it myself after reading some other posts.. <br />Thanks guys

 

[KaGee]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

If you can't get the thing to idle below 1500 it's time for you to stop trying snake oil and actually start to solve the problems.<br /><br />You still have a carb issue. Get it replaced or rebuilt. When was the engine last tuned up with new points, rotor, cap and plugs?<br /><br />650 -700 is proper idle speed. If engine will not idle down that low, troubleshoot, isolate the problem and fix it. As said above, trying to shift @ 1500 will tear up the clutch dog and require a minimum of a new clutch dog and gear set at a parts only cost of over $600.

 

[KaGee]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

OMG, after re-reading, starting to sound like Don. Sorry, I apologize.

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

KaGee, I agree with you. But what im asking is that is it possible that carb is not as bad as just the setting. Engine has not been tuned up for a long time. I acquired the boat and found it it had engine bearing probs. I was after that since. Now ive got that fixed n trying to look into tuning issues. Everyone here is suggesting me to go for the carb right away without telling me to first try the tune up and then if that does not help go for carb.<br />Im also suggesting that the guy who fixed up the bearing might have messed up the carb setting as boat was not idleing at all and stalling on nuetral because of the bad gas it had in there.<br />Now ive got rid of bad gas and changed old oil and filters and was thinking that a carb tune-up might solve the prob. If not then I would head up for carb rebuild. Please suggest me on this guys.<br />If you gurus think there is no worth trying tune up and carb adjustment then I would definatly head on for carb rebuild. <br />Sorry for my questions this is my first experinece with boats ever and Im learning a lot.<br />Thanks once again for support.

 

[rojoc]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

I think you might start by disconnecting the linkage from the carburetor and see if the engine will idle down wth the linkage off. Run the engine and see if this makes a difference. There should be an adjustment at the very end of the cable. Chapter 4 of omc cobra manual has a few pages on adjustments. Good luck

 

[ahein]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

Rox,<br />If I'm following you correctly, you're saying that the mechanic that replaced the engine's bearings may have turned up the idle adjustment to 1500 rpm because he couldn't keep the engine running at the proper idle rpm. This situation apparently was due to bad fuel. You have since replaced the gas with fresh fuel and changed the filters (what about the screen in the fuel line at the carb body?).<br /><br />May seem like a silly question, but have you tried turning the idle stop screw on the carburator linkage to bring the rpm's down to 650-700? There is a small, spring-tensioned screw on the linkage that is adjusted to set the throttle cable position when in neutral. Turning it counter-clockwise will reduce your rpms and vice versa. You may not need a carb rebuild at all! If you can get your rpms to drop to 650-700 without stalling the engine, then try some seafoam to clean things up and rermove any deposits, varnish, gum, etc in the carburator. The other thing you need to do is check your timing after you get your rpms down. If the mechanic set your timing while idling at 1500 rpm, it will be wrong when idling at the proper speed. Timing should be set after the engine is properly warmed up and in gear (be careful).<br /><br />My point is, try the basic things first to solve your problem before trying to tackle a carburator rebuild.

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

ahein, Thanks for you suggestion. I will try to do that today runing on muffs. I do strongly belive that trying basic things are worth the effort. <br />As you mentioned about SeaFoam I put one pint in the gas tank along with fresh oil. I was reluctant to put it directly into the carb. Is it ok to spray some SeaFoam in carb while engine running. Please explain lil further how you mean to clean carb with SeaFoam. While engine running to stopped. Clean it with some soft brush using SeaFoam?<br />Thanks for you help.

 

[rizy1976]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

Update on progress. While im still preparing to do a carb job, reading documents and postings. I decided to try to do some ajustment as I understood from readings. I did manage to pull the rpm down to 850 by ajusting idleing needle. I hope it goes down further when taken to water. I'll take the baby to water this weekend and observe performance. Although I do plan to do a carb job sometime later after getting some more understanding of carb working and parts.<br />Ill keep ya guys posted as I progress. <br />Thanks

 

[Gary H NC]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

If you have never rebuilt a carb that four barrell may be a challenge.<br />Again,you should unhook the throttle cable at the carb and get the idle down..then adjust throttle cable a turn or two and re-connect it...<br />If you got it to idle at 850 you should get it down a little more once in the water..

 

[lilmandavis]

Re: 5.7 OMC Cobra 1988..Another Carb Prob..

no matter how much cleaner you dump on that carb, it will never get to where it needs to be. all the little holes inside need to be wired out and blown with compressed air. if your butterflies are dirty the cleaner will only clean them and the outside. if you just had your engine rebuilt, why not spend another hundred and rebuild the carb. last gear set i bought was 1400 for my cobra. if boating was cheap and easy, everyone would have one! i think that if i had a fresh engine i would make sure that the componets on it are up to par. not half azz