mercury 9.8 starting problems

[jim_in_day]

Hi everyone! Well, we have been working on the 9.8 for a while now, installed new coils to get spark, We.ve been thru the carb 3 times now, with a fine tooth comb, cleaner, cleaner, air, kit. We rebuilt the fuel pump. It will not start until you either pour fuel down the carb throat, or manually advance the throttle to about half throttle and hold it there while you pull your arm off. Once it starts, it will restart on the first pull. Let it get cold (ie sit for a day or so) you have to start the procedure all over again. It responds to adjusting the idle air/fuel mixture screw, and when we get the sweet spot it seems to idle just fine for a while, then the low speed idle seems to quit working. The customer is getting tired of it not working, but we just cannot make it cold start reliably. What is the secret? This is a CD ignition not points motor serial number 5640028

 

[Laddies]

Re: mercury 9.8 starting problems

It's for sure you have a lean problem on the low speed, I know you have cleaned the carb and am not trying to upset you any more than you are but I have a few ideas, 1 is the plastic venturi in the carb, 2 have you removed the high speed nozzle and the brass plug on top of the carb and cleaned the low speed pickup tube, while your at it pull the soft plug and clean the low speed fuel hole under it. If none of this helps is the inlet needle one with a spring on it, if not change it and set the float about 1/32 above the max height that mercury recommends which would be 7/32" instead of 1/4" we have had to do this on a couple engines, we also found that some chokes are 2 piece and had to solder them so the would not open when cranking the engine and last but not less the lock on the choke cable not working properly.

 

[jim_in_day]

Re: mercury 9.8 starting problems

Thanks a bunch. I just got done tearing down the carb (again) and found that the inlet needle didn't have a spring on it (like the parts diagram calls for) so that was wrong. Also the plastic venturi was broken, one of the arms that centers it was missing, but it appeared to be positioned correctly, but I will be replacing it anyway. All the passageways were clean, (I removed and inspected per your suggestions) and the choke blade is a one piece design, so that was ok. We will probably also replace the float, as it looks a little ragged.(besides we are in there now. Somebody else was in this carb before us, so we are cleaning up someone else's mess.