Stubborn '75 7.5hp Mercury

[jon75127]

Can't get it started. Disassembled and cleaned carb and fuel pump. Have good spark and compression. Plugs are wet...fuel getting to cylynders. You can tell it really wants to start, it just can't. Spray carb cleaner into carb, it starts and dies. Pull rope again and it starts and runs for a short time. Pull the rope again and again...nothing. Pull the plugs again, and they are wet from fuel.

Is there something in the electronic box that locks out for some reason? Any ideas??

 

[billybones]

Re: Stubborn '75 7.5hp Mercury

does your choke work? Mine when cold even on a 90 dgree day needs full choke. 3 pulls Starts and dies. then Half choke starts 3rd pull runs a minute and then you push in choke and it runs fine rest of the day on 1 pull. before I did a link and sync though I had to put it past the start position. My throttle was off from what the handle said it was. Not enough for start. weird how that gets off position at all. HTH.

 

[tashasdaddy]

Re: Stubborn '75 7.5hp Mercury

have you checked spark with a spark tester, and compression what are the numbers.

 

[Chinewalker]

Re: Stubborn '75 7.5hp Mercury

I agree with Billy - check your choke. The linkages on Mercs are notorious for loosening over time to the point where the choke doesn't choke - it just kind of loosely gags the carb a bit. You need the full choke. Being that it starts on carb cleaner (which you should NOT do - use a spray bottle with mixed fuel!!) it sounds like a fuel issue... Do you get fuel dribbling out the throat of the carb after choking it? It's either not drawing fuel or not getting fuel. Not drawing might mean stuck reeds or bad crankcase seals. Not getting could be a plugged fuel line, stuck fuel pump flapper valves, incorrectly installed fuel pump gaskets, plugged carb passages or pinched fuel line.

- Scott

 

[jon75127]

Re: Stubborn '75 7.5hp Mercury

I did notice the choke is spring loaded and will not choke 100%. It springs open to about 80% choked at best, moving the knob with it...no adjustment.
Gas does run out of the throat of the carb. Did spray gas mix into the throat, but would only start on carb cleaner.

 

[Chinewalker]

Re: Stubborn '75 7.5hp Mercury

There is a bit of adjustment available. The small plastic piece on top of the carb that anchors the choke bowden wire to the carb has an oblonged hole in it. It can be adjusted for max choke closing...

- Scott