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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10894
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a very faint spark at plugs. I put a new power pack

Customer Question

I have a very faint spark at plugs . I put a new power pack and a coil on and still light spark also new ignition switch . will not start.
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
I had some local look at problem had it running in 30 min , I picked it up got home wont start ,, went back he messed with wires for power pack started ,, went home started ,, went to go fishing wont start and has not since . That's when I put ign sw and power pack and coil new and that is where I am at now
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

The only thing left that willl cause weak spark is the stator. You have eliminated the power pack and the ignition coil leaving the timer base and the stator. We can rule out timer base as you have spark it's just weak. Just by process of elimination the stator is the only thin g that it can be. Now if we have an issue with the stop circuit it could have an affect on quality of spark. This we can eliminate by disconnecting the black/yellow wire from the power pack. If spark is still weak then the stator is bad.

Could I get the complete engine model number to get you the part number for the stator.

Post back with questions.

Customer: replied 1 year ago.
I have unplugged all harnesses from engine and the black and yellow wire . I use a hand held remote starter switch to turn engine over with . I have to cup the spark light tester to see that there is a faint spark , there is fuel on plugs also every time I check them .
Expert:  Tan replied 1 year ago.

Then the stator is bad. Replace the stator. The stator isn't putting out enough voltage to fire the spark plugs under compression.

Customer: replied 1 year ago.
I have installed new stator and still no fire .....Anything else to check ?
Expert:  Tan replied 1 year ago.

You said you replaced the power pack was it a new power pack or used?

Disconnect the blk/yel and check for spark.

Customer: replied 1 year ago.
new power pack . coil was used but good ?? I replaced old coil to engine and still no fire . stator ohm test brn to brn/yellow 0
or to or/bl 399 wh to blu and wh to gr 27 ea
Customer: replied 1 year ago.
the old stator tested those # ***** new
Expert:  Tan replied 1 year ago.

Well the old stator was definetely bad. Disconnect the black/yellow from power pack and check spark.

The timer base is in spec 15-50 wht to blu and wht to green 27 ohms. The stator is new and the power pack is new. That leaves a short to ground.

Expert:  Tan replied 1 year ago.

Are you sure the pins are installed in the plugs all the way? If the pins aren't in enough to make contact you won't have spark.

Customer: replied 1 year ago.
I have tried without black/yellow same issue .I have also checked pins .I will check on grounds . get back to you . thx
Expert:  Tan replied 1 year ago.

Ok all the components being new is strange. The only thing I can think of is weak magnets in the flywheel.

Customer: replied 1 year ago.
magnets seam strong to me on fly wheel. all pins are making contact . could not find any bad grounds . how does system work ?? when flywheel spins it sends fire to power pact then to coil ??? I need to see where it starts and stops ,,what tests should I do ??
Expert:  Tan replied 1 year ago.

The system works when the flywheel spins past the stator producing voltage that goes to the power pack then the timer base tells the pack to fire each coil intern firing the spark plugs. The main power comes from the stator. The test you need to porform will require a peak reading volt meter or a DVA adapter.

Here is the adapter you need to test.

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