Mercury 18XD issues

[dwfizer]

I have a mercury 18xd with a push button starter, that has run flawlessly since I have owned it. It sat all winter. I took it to the lake to test it out this past weekend and although it took some time to get it started, it finally did. When I gave it some gas it started to take off like it normally would then I realized that I had the throttle handle at far as it would go toward full throttle. The boat was just plowing through the water - no where close to up on top. Then about 3 minutes later - still with handle turned to full throttle - the thing takes off and ran like it has in years past. Thinking back, it could have been only hitting on one cylinder then the spark may have ignited on the second cylinder, maybe? I am not sure how to trouble shoot that spark problem. The other problem I have is that it often times stops running when i put it in neutral. It basically will not run in neutral. It just dies. I do not run ethanol, rather all my gas is non-ethanol 91. I am beginning to think this is a fuel system problem... I think I am going to replace my fuel line and bulb then if this problem doesnt go away, I'll take the carb off and rebuild it. I'd love some advice for this somewhat complicated problem.
BTW thank you in advance

 

[racerone]

Not related to your issue, but have you installed a new water pump impeller in the last 5 years.----If not it needs one.-----Do a spark test.------Good spark will jump a gap of 3/8" ( 1 cm ) on a test device.----Report what you find.

 

[dwfizer]

Not related to your issue, but have you installed a new water pump impeller in the last 5 years.----If not it needs one.-----Do a spark test.------Good spark will jump a gap of 3/8" ( 1 cm ) on a test device.----Report what you find.

thank you for your help! I have not installed a water pump impeller and not exactly sure how to do that... but if it has to do how much water is coming through the pee hole - I checked it when it was running and there could not be more water peeing out of the hole.
Nonetheless - you were right on with the spark test - the top spark plug was full of fire with none going to the bottom plug. there seems to be an ignition problem! The positive thing here is that the engine turned over and started to run with the bottom plug out!
the question I have is what are the likely problems? bad plug wire? does the plug wire unplug from the blueish piece with the two leads coming off it?

 

[dwfizer]

thank you for your help! I have not installed a water pump impeller and not exactly sure how to do that... but if it has to do how much water is coming through the pee hole - I checked it when it was running and there could not be more water peeing out of the hole.
Nonetheless - you were right on with the spark test - the top spark plug was full of fire with none going to the bottom plug. there seems to be an ignition problem! The positive thing here is that the engine turned over and started to run with the bottom plug out!
the question I have is what are the likely problems? bad plug wire? does the plug wire unplug from the blueish piece with the two leads coming off it?

ok - I have replaced both coils, plug wires and spark plugs and still have no spark to the bottom spark plug. I don't know where to look next. Any help on this owuld be great. I can tell you that before i took it out of the water it would run on one cylinder until it warmed up then the second would kick in and it would run fine. please offer any assistance on this.

 

[dwfizer]

So why no replies? Are you guys just as stumped as I am?

 

[racerone]

If you are into just replacing parts you might as well change the switch box.

 

[flyingscott]

Your switch box is probably bad and probably always was.

 

[dwfizer]

If you are into just replacing parts you might as well change the switch box.

Not really into randomly changing parts - I AM really into fixing the problem. I’d love to figure out the root cause of the problem! Thoughts?