I have a 2001 Mercury 90hp with a hard start. At first start up the motor runs great no issues and idles fine. Now i do have to slam it into gear quickly to keep it running on take off, but other then that It will run me up and down the lake until I turn the motor off to fish. When I try to restart the motor, the motor would take 2 to 3 minutes to restart again. I have throw every part I could at this motor, from fuel bulb, fuel pump, coils and wires, new fuel lines, cleaned crabs several times, themastat, choke and spark plugs. The only three items I have not replaced are the flywheel, stator and trigger, which I believe are OK because the motor runs great at startup. Does anyone have any idea what this could be. The only thing I can think of is adjustment of the air idle screw on the carbs or shift cables.
I had a 2002 90. I didn't boat very often and when out for the first time after a long dry spell, It's thirsty. Bulb has to be hard and battery needs to be topped off. Key needs to moved to the ON position and pushed in for about 30 seconds prior to activating the starter to get some fuel to drain (choke function) into the carbs Venturi from the "fuel enhancement" solenoid circuit. After that 30 seconds, while the key is still pushed in, roll the key over to start. If the engine lights off but struggles, the key will be in the ON position, the engine is fixing to die, just push the key in and hold it for more fuel prime....the engine should respond and come back to "fast idle" RPM because you still have the "fast idle" lever up. After 30 seconds of that, you are still in N gear, reduce the fast idle lever to the OFF position and engine should idle smoothly....if not give it another squirt of fuel by pushing in the key.
Once started the first time it lights right off (for that particular outing) and has warmed up a bit...time depends on ambient temp., the shifter position change from N to F or R should be accepted and the engine remains running.
Side note: After running to a fishing spot, if I only stop for a few minutes, it starts immediately when ready to leave doing nothing but rolling the key to Start. If I sat for 15 minutes or so, It needed the fast idle lever raised at least and if longer or if that didn't get it started, then in addition to the fast idle lever on the remote all the way up, a push in on the key while cranking to get some "fuel enrichment" function flowing should bring it immediately on line.
The service manual for that engine says RPMs at idle need to be 675 +/_ 50. It continues to add that the idle setting, (set by the spark advance lever adjusting screw) is slow enough to allow for shifting without grinding the lower unit gears, yet fast enough for the engine to not quit running.
With the information you posted, I'd say your idle RPM is set too low/slow. If that doesn't cure the problem, its a good place to start troubleshooting.
One other thing is that the "low speed" carb (spring loaded) screws on the side of the carbs need to be set lean but not too lean. They need to be set so that the boat (just) takes throttle effortlessly when clearing the "no wake buoys" and you "firewall" the throttle to get on plane......not partial throttle during the plane-out. Subsequently, after being on plane, then cutting the throttle back to your desired speed if you are interested in a "cruising" speed.
