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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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A 351 inmar is having trouble firing(spark). When a SUV

Customer Question

a 351 inmar is having trouble firing(spark). When a SUV added power through jumper cables it fired. Put a new battery in, not the solution. Put a new coil in, seemed to be the solution, launched boat, engine stuttered consistently at all levels of throttle, soon snubbed out and would not fire again. Now what? Sure would appreciate some guidance from someone who knows about these sort of things. Boat is a 1988 supra direct drive.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

We need to check voltage at the ignition coil when cranking the engine. What is the voltage reading. You want to check on the positive side of the ignition coil key on and cranking.

Customer: replied 1 year ago.
Sorry Tan, I do not have a voltage reader. I can get one though. Any info on what different voltage readings would mean?
Expert:  Tan replied 1 year ago.

The voltage will need to be around 10+ volts cranking and 12 key on electronic ignition. If you have points ignition you must have 7-10 volts key on and 10 volts cranking.

If voltage is low on either test we have a voltage delivery issue. This can be many things. We will need to check the voltage at the key switch red wire key on and cranking.

Post back with your readings.

Customer: replied 1 year ago.
Thank you Tan, took a reading with a voltage meter, very low, hardly reads anything with key on or as engine is turning over. there has been a few times where the engine will not turn over, just one click instead...
Expert:  Tan replied 1 year ago.

Ok this is a sign of a bad connection or bad cables at the battery when the solenoid only clicks. If the engine cranks now get a piece of wire and run from the positive side of the battery to the positive side of the ignition coil now does engine start and run?