80hp Merc-IDLES fine, Won't Run

[vmuse]

1979 80 HP Mercury 4 cyl outboard<br />She runs great in the yard. Out on the water, starts right up, idles fine, but when you push the throttle down it bogs down and stalls. If you pull back on the throttle, it may not stall. IF you push the throttle down and hold in the choke until the rpms get up to speed, then release the choke, the motor runs fine until you back off on the throttle.<br />It is not the fuel filter - it's clean. The fuel line and ball are fine.<br />We are planning on ordering a carb kit, as the gaskets show wear.<br />Has anyone seen this before and do you think it is the gaskets? I read a post from someone having a similar problem - said they rebuilt the carb, and still had the same problem.<br />THANKS

 

[Trent]

Re: 80hp Merc-IDLES fine, Won't Run

Yep........Seen this hundreds of times!! Your going in the right direction. Time to CLEAN the carbs and install kits!!!!!!!!

 

[SteveI]

Re: 80hp Merc-IDLES fine, Won't Run

Trent, I have the same problem with my Merc. I rebuilt the carbs and that didn't fix it. I have adjusted the timing, checked out the coils etc. Still no fix. Someone suggested some plastic bleed inserts may have been spit out. I can't find any reference to them in Clymers. Can you fill me in on the subject? Where do you find them? I am a DIY'er. How do I go about replacing them? Any insight / help you can provide on this would be great.

 

[Kenny Bush]

Re: 80hp Merc-IDLES fine, Won't Run

Vmuse, if your timing is on the money, and the cylinder pressure are within 15% of each other, then you have a fuel problem. I would proceed on the carb kits but I am thinking by the sound it that you have a reed valve problem. It could be that some of reeds are relaxing open. I have found in past cases where motors with throttle response problems(after eliminating timing and synchronizing) especially after deaccelleration tend to be reeds. If the reeds stay open greater than .020 you lose a great deal of the case pressures (+ and -) in each chamber that affect fuel flow. I would kit the carbs for sure......while there off, inspect your reeds for this condition. Sounds like your engine runs fine idle or wide open. If the engine gains and deaccellerates ok when you move throttle very slow starting and stopping, then most likely its the reeds. The motor basically cannot hold its suction at a steady rate due to leekage......<br />Anyway hope this helps............

 

[SteveI]

Re: 80hp Merc-IDLES fine, Won't Run

Thanks for the input...... <br />I have had the carbs off and looked at the reeds. None appeared to be relaxed causing a gap however, I could only see the very front ones. How do you inspect them all? Does one need to crack the case?<br />Would a problem with the reeds cause it to run rich. Another symptom is that it smokes and you can smell gas at low rpm's. When I try to lean it out, it starvs out when I throttle down heavy. The plugs fowl fairly quickly. I have cleaned them and still experience the same problem. This has been a very confusing problem to me however, I am sure it can be solved. I'm ready for the next step. What do you think?