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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10979
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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It was running perfect, died at wot ,now wont start, it has

Customer Question

it was running perfect , died at wot ,now wont start
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: it has fuel and spark
JA: Is there anything else the Marine Mechanic should be aware of?
Customer: it turns over but seems to not have compression , so i figure it jumped timming but was told thats not possible on the 3.0 mercruiser?
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

The gears would have to break for the engine to jump timing.

Are you sure it is fuel and not water?

Have you done a compression test yet?

Customer: replied 1 year ago.
I have not done a compression test but can tell with my finger on spark plug hole there's hardly any pressure, and the rotor is turning , I do have spark to all plugs, and no it's gas in coming out of the carb, turning over the engine sounds like no fire
Expert:  Tan replied 1 year ago.

The odds of loosing compression on all cylinders is very slim. Now I have seen the distributor shaft brake on these engines. Pull # 1 spark plug out hold you finger in the hole crank engine over till it blows your finger out of the plug hole. Now look at the harmonic balancer is the timing mark on the balancer line up with zero on the timing mark?

Then remove the disatributor cap is the rotor pointing to the # 1 spark plug?

Customer: replied 1 year ago.
Timing mark on zero , piston is at top dead center rotor is pointing at wire to cyl 1
Expert:  Tan replied 1 year ago.

Ok check voltage at the ignition coil key on. What is your voltage reading? How strong is the spark?

Customer: replied 1 year ago.
Customer: replied 1 year ago.
Spark didn't seem very strong but again turns over with almost no drag or attempt at cranking
Expert:  Tan replied 1 year ago.

Ok now crank engine and check voltage at the coil. What is your voltage reading?

Is this electronic ignition or points?

Customer: replied 1 year ago.
Electronic has a modual under cap
Customer: replied 1 year ago.
I can't crank it and read voltage
Expert:  Tan replied 1 year ago.

Ok All you need is a jumper wire and jump from the battery cable connection to the yellow/red wire on start solenoid with key on. We need to do a compression test.

Customer: replied 1 year ago.
Spark I noticed was barley lighting up my timing light
Expert:  Tan replied 1 year ago.

That's why we need to check voltage at the coil when cranking. Do this can you get a jumper wire and run the wire from the battery cable connection on the starter to the positive side of the ignition coil. Now crank engine does it want to start?

Customer: replied 1 year ago.
Cranking voltage is 10.68, I have the coil off now but has to be unplugged to test voltage to it , and boat has been cranked and cranked sounds like no fire , but battery may be getting low
Expert:  Tan replied 1 year ago.

Ok we need somewhere around 12 volts to have good spark. For the engine to just quit I'm thinking an ignition issue. The spark should jump a 1/2 gap when held from the top of the coil when cranking and it should be a bright blue color.

Customer: replied 1 year ago.
Spark will ark across a 1/2 gap but is yellow orange not really blue
Expert:  Tan replied 1 year ago.

THat kind of spark will not fire under compression. We need to get 12 volts to the ignition coil. Does you volt gauge show that the engine was charging when the engine was running?

We could have a voltage issue due to alternator failure.

Customer: replied 11 months ago.
Valve broke in cyl 3 tore up piston knocked hole in it!!
Expert:  Tan replied 11 months ago.

See that would have shown up in the compression test I ask if you had done in my first reply.

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