Thread: help with 6hp merc

I have problems with my 1986 mercury 6hp serial A0963511. Hard to describe the problem, it starts great, idles a little on the high side, but starts popping after just a few seconds. It like I said makes a pretty loud pop noise, every few seconds (4-10) and seems to slow down, like its shuts off but right away runs again, every time it pops it blows a stream of smoke out the exhaust. I am afraid to take it out on the lake, or rev it up in the barrel. I had to put a stator on the first of last year and two years before that also, it ran ok after that, but haven’t used it much. If I had this problem on a car I would be looking at the ignition, but where on a boat motor? I do have a spark tester and seems to have a good spark all of the time. The compression is 90# in both cylinders, but tester is suspect, as I had a bad bottom valve stem and only the one I could get to work was the stem in the release valve. Evidently they take a special valve stem for compression testers. I checked the timing and it is about 2 degrees advanced from the 6 degrees recommended at idle, the idling would not slow enough to put the mark on the 6 degrees. Appears to me you can’t really change the timing anyway, factory set? Carburetor was serviced 4 years ago, but they did a lousy job. Brought it back and wouldn’t start. I found they lost and didn’t replace the spring under the choke primer. I just looked at the carb. and blew it out, it was very clean. I did put it together without new gaskets, only putting vaseline on them. This was yesterday after the problem had started. I sure can’t figure how to check the float height, and the (new) plugs seem to be pretty wet. The gas is new, and correct mix. I have changed the tanks and have a new hose assembly. With a clear hose I was getting quite a lot of bubbles in the gas line, so hooked direct from the gas tank to the carburetor bypassing the fittings and the fuel filter. No improvement in the popping. Any suggestions will be appreciated. Thanks

Sounds like it is running lean ,richen the mix or could be reed valve or gasket behind reeds

If it is running lean and that is what it sound like, you need to get it fixed. A lean running motor will overheat and pistons will start melting soon afterwards. Try adjusting the jets. If they are the fixed type, the carbs will have to be disassembled, thoroughly cleaned, and reassembled with new gaskets, needle and seat.

My guess is a broken reed......

Yea definately sounds like its loading up and running lean. I dont have much experience in Mercury so I dont know if it has a slow speed idle mixture. Probably needs the carb rebuilt by someone experienced and should be good to go. Its a simple fix most likely so take it to someone experienced.

Thanks for all of the good advise and ideas. Seems like the general consensus is a lean condition. I pulled the carb again today & checked the reed valves, they were fine. It will not run any better when I open up the idle needle, so pulled the carb and will order a carb kit and try again one more time and then to the shop. Again thanks
Luck