No spark but engines cranking. Need help

DazeOff

Went to start the engine this AM and it started with no problem. Ran for about 10 seconds, sputtered and shut off. Restarted for a few seconds and that was it. I thought maybe my fuel gauge was a little off and I ran out of fuel. Put in a few gallons, tried starting and there was nothing. I have a carburated, mercruiser 5.7 350. Checked the carb and it was pumping fuel into the chamber when the throttle was pumped so I know it was getting fuel. I checked to see if I was getting a spark but there was nothing. Looks like I'm not getting anything out of the ignition coil which is what I'm hoping is the problem. The question I have is this. Even if the coil is bad, should't it register on a volt meter when I turn the ignition on and touch the positive side of the coil terminal? If it should show 12 volts (not showing anything now) even if the coil is bad, what else could be blocking the juice? Any troubleshooting tips would be recommended. 

Thx in advance

99270fv

try hooking a jumper wire from the positive side of battery to the positive term on the coil, and then check for spark

reneechris14

What about the 50amp circuit breaker on the back off the motor

Wildboating

I would check the circuit breaker and fuses first.   Then you need to check the crank position sensor.  If the ECM does not see it it will not send voltage to the coil.

DazeOff

@reneechris14 is thathe the one that is square and looks like piece of plastic? How would I test that?

DazeOff

@reneechris14 the red reset button on the breaker is fine, not popped requiring the reset. What about the 90 amp fuse by the starter? Would that stop the starter from cranking or cut the connection to the coil?

duane.mosley

kill switch gone bad interrupting voltage to coil?

reneechris14

I would think the easiest test would be 12v on the back of the alternator. I believe that wire runs from the battery to the starter to the alternator. How can you check the neutral safety switch and kill switch. But you did say it cranks over.

DazeOff

@duane.mosley Are you referring to the kill switch on the shifter? Anyway to bypass that to test?

DazeOff

@reneechris14 Yes, it cranks so the starter is working.

Stodge

If you can access the back of that switch you can test the switch with a ohm meter.  

Cableguy Greg

That sounds like the kill switch to me. Turn it off and on a few times then try starting it again.

rasbury

I have, I think 3 times, accidently bumped that darn switch and freaked out until I turned it back on....by pass it and see if that is it. Have to start from the front and work your way back anyway I suppose...

duane.mosley

that kill switch allows the starter to crank but kills the spark to the coil. i would imagine there is an access panel below the shifter handle so you can access the wires behind the side wall. i have a 250 and we were all over my boat one day trying to figure out why it was cranking fine, but no spark. i knocked the thing lose. just a thought and sure would be sweet if that was your only issue. that's a cheap fix!
 good luck

Wildboating

Go to the ignition control module, it sends spark to the coil.  You should have 12v on the purple wire.  If not work backwards.  

steeledp

When everyone says kill switch for you mean the safety switch in the throttle ?? I’ve been having to wiggle the throttle levers slot to get my boat to allow key to start enigines. At times. Now my starboard engine will turn over but not start !! Any suggestions How do I access that switch in the throttle handles 342 2006

212rowboat

Does your warning buzzer sound at key on (as it always should with thunderbolt ignition due to no oil pressure being present before engine start)?... if it DOES NOT, the issue is with your key switch, and yes, key switches go bad.  

You may not be energizing your coil, which relies on the ignition module when it is passed through from the helm (key switch) bridging the juice.  

That little 90a fuse block that is attached to your starter is also suspect... the stud that holds it on should also hold the starter cable-to-battery and is your engines main power source... the little block feeds ALL your harness power... engine will turn with it being blown but there won't be power otherwise to the engine.  You CAN bypass it by placing the harness wires under the main cable, but i wouldn't rec running it like that constantly.