What The??

Hi, I currently own a 98 15hp Mariner and lately when warmed up and in forward gear and at a very low rev the engine occasionally coughs/knocks, drops in revs for a second then picks back up in a puff of smoke this doesn't happen very often other than that it idles smoothly and runs very well at high revs. At times on the water it sounds as if the leg has hit something but the engine never completely stalls. I have changed the plugs and the old ones showed no signs of fouling. I did today notice what looked like fuel separation in the tank (a thick oily jelly in the bottom) and this maybe the cause of my problems and if so wouldn't the engine be running rough all round?? I have read in other posts that the hitting sound when under way maybe caused from a problem with the gearbox but i checked the condition of the gear oil and the magnetic plug for filings and everything looks great as well. So I'm stumped any ideas would be much appreciated... cheers Dazza

Re: What The??

The stuff in the tank should be dumped and new fuel put in then run for a bit to see if that take care of the problem if it don't richen the low speed about 1/7 to 1/4 turn

Re: What The??

yeah out with old and in with the new fuel that is !!

Richen the low speed 1/7 to 1/4 turn?? do u mean mixture screw??

Re: What The??

Yes

Re: What The??

Well I replaced the fuel and cleaned out the fuel filter. Turned the mixture screw in to richen it up. Still no good problem still remains.

Any other ideas guy's???? Stuffed reed??

Re: What The??

"bump"

Re: What The??

idle mixture screw should be turned CCW to richen

What you are discribing sounds like a lean idle cough

if the idle screw adjustment does not cure the problem it could be that the air bleed may be slightly dirty and restricted, it could be time just to disassemble the carb to totally clean all passages completely.