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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11079
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 2012 3.5 that ran great the last time I used it

Customer Question

I have a 2012 3.5 that ran great the last time I used it about three weeks ago. Today I can not get it to start and it's dumping fuel. It seems like a no spark problem. I took the plug out and cleaned and dried change. It's still dumping glass out the line coming out of the top of the carb to the bottom of the housing. Any chance it's the dead man switch ? What do ya's never dumped gas before either. Thank you....Chris Gallagher
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello Chris. Mt name is Tan.

With the carburetor dumping fuel the engine will seem like it has no spark. The cylinders are flooding with fuel and the spark plug will not fire.

The inlet needle is stuck open either from debris or it is just stuck. The carb will have to be removed disassembled, cleaned and reassembled.

To know if you have a spark issue you will need a spark gap tester to verify spark. The spark must jump a 7/16" gap on a spark gap tester.

I would start with removal and cleaning of the carb first. You might fix the carb and not have an issue.

Does this make sense?

Customer: replied 1 year ago.
I can try. We are in a anchorage and won't be home for a week and I'm screwed without it so I will try.
Customer: replied 1 year ago.
I don't have a spark tester on board
Expert:  Tan replied 1 year ago.

The carburetor should never dump fuel even if you had no spark. So it isd most likely that the cylinder is so full of fuel the engine won't crank. It isn't likely you have lost spark.

I'm sure the carb issue is the problem and can be resolved just by cleaning the carb. If you have access to parts I would buy an inlet needle/float valve.

Just to check for spark you can remove the spark plug and ground it to the engine block and crank engine. Or remove the spark plug wire and stick a screwdriver in the plug boot and hold screwdriver away from engine ground about 7/16" crank engine.

Post back with questions.

Customer: replied 1 year ago.
I do not have access to Parts but I'll try cleaning it...thanks
Expert:  Tan replied 1 year ago.

Since the engine was running recently it is most likely just some debris in the needle holding the valve open.