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idle low speed misfire making me crazy

N

nemer

Contributing Member
1979 175 mariner. I have cleaned the carbs put in new needles and seats in, set the floats 1/16, I set the timming. The motor will idle fine sometimes for a complete runs throught the throttle. As much as an hour of runtime. Then the next time I use the boat it starts to misfire at idle. Then sometimes at a round four thousand rmps it will act like it needs fuel so I hit the gas and it jumps right back up. It does none fo the following on a consistant basis. Could it be the floats? I tried to buy replacemant plastic ones, but they didn't fit. Any ideas? Man I just want to fish!
 
If this is a QUICK skip, then it's electronic (ignition related). A slow skip--more like a sag-- then it's carburation. I suspect a bad coil(s). Seen a few of them lately.

Jeff
 
It happens every 2 to 3 seconds. It is not a backfire it sounds like air exhaust. One time I gave it shots of quick start into #3 and it smotthed out. So I put a new coil on 3 and took the carb back apart and the float was a little off. I just went through the timming and sync steps again. I will take it to the river tomorrow and let you know. It never misses a beat in the drive way until it starts it in the river. Then when I run it in the driveway it will miss fire. When I pulled the fuel line today brown fuel came out. I squeezed the ball a few times until it turned back to blue. I am going to run this tank out and flush the tank too. Very strange because it is an aluminum tank.
 
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