2012 242 alternating misfire

[Skin6061]

My 2012 242 started misfiring on startup. So this is kinda odd. Been using the boat all summer and no problems. Toom the boat out started up and ran just fine off the trailer and head to the first beach. Leave from the go.to the marina have lunch and when we leave no issues. Go to the last beach and hangout a bit and when we leave only one engine fires up. Get the second engine to fire but one engine sounds like it's misfiring. Shut both engines off. Turn off all batteries and wait ten min to clear codes and reset ecu. Now this is where it gets weird. Fire the port side no problems. Fire the starboard side it fires no problem but the port side start misfire. Shut off port and troll at idle to boat ramp. Wait a few min fire the port side and then the starboard develops a misfire. This goes one another two times alternating misfire. Checked voltage on the guage with the running motor and it was at 13.1 volts. Tried one more time and the motor fired and the other one did not misfire and everything was back to normal. I assumed I had a voltage drop when firing the a motor that caused the other motor to misfire. I was thinking a dead cell in the starting battery. But with the guage showing 13.1 volts Im thinking I may be missing something.

I have three batteries one start battery one house battery and one battery for my amp. All on there own switch and I use a battery maintainer between lake trips.

Has anyone ever experienced something like this before and can guide me to what may be the cause of my problems?

 

[Babin Farms]

Have you load tested the starting battery or checked the connections? I know from experience that a weak battery/bad connections will cause some weird things to happen.

 

[Julian]

My 2012 242 started misfiring on startup. So this is kinda odd. Been using the boat all summer and no problems. Toom the boat out started up and ran just fine off the trailer and head to the first beach. Leave from the go.to the marina have lunch and when we leave no issues. Go to the last beach and hangout a bit and when we leave only one engine fires up. Get the second engine to fire but one engine sounds like it's misfiring. Shut both engines off. Turn off all batteries and wait ten min to clear codes and reset ecu. Now this is where it gets weird. Fire the port side no problems. Fire the starboard side it fires no problem but the port side start misfire. Shut off port and troll at idle to boat ramp. Wait a few min fire the port side and then the starboard develops a misfire. This goes one another two times alternating misfire. Checked voltage on the guage with the running motor and it was at 13.1 volts. Tried one more time and the motor fired and the other one did not misfire and everything was back to normal. I assumed I had a voltage drop when firing the a motor that caused the other motor to misfire. I was thinking a dead cell in the starting battery. But with the guage showing 13.1 volts Im thinking I may be missing something.

I have three batteries one start battery one house battery and one battery for my amp. All on there own switch and I use a battery maintainer between lake trips.

Has anyone ever experienced something like this before and can guide me to what may be the cause of my problems?

First thing I do when this happens is check electrical connections, 2nd thing is to replace the spark plugs (unless they were JUST replaced). How old are the spark plugs?

 

[Skin6061]

First thing I do when this happens is check electrical connections, 2nd thing is to replace the spark plugs (unless they were JUST replaced). How old are the spark plugs?

Spark plugs were replaced during oil change and after last season. Did not have the proper tools with me to check while on the water. I did check electrical connections at the battery to see if anything was loose but found nothing. Planning to take tools with me this weekend and give the boat a though check over and see if I can pin point the issue.

Does anyone know how the fuel system works. Does each engine have its own fuel pump in the tank or do they share one fuel pump?

And does anyone know what voltage I should be getting off the stator at the battery while the engines are at idle. I know my car is suppose to be around 14 volts but it has a alternator where the engines do not.