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Dominick
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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I have a 2006 Mercury 25 EFI and accidentally reversed the

Customer Question

I have a 2006 Mercury 25 EFI and accidentally reversed the battary leads . First symtom was no power to the engine / would not crank. I found a blown fuse in the yellow fuse block on the top starboard side of the engine. Replaced the fuse and the engine started instantly, I shut the engine off quickly ( as the boat was trailered ). Tried 48 hours later to start the boat, excessive cranking, found to be no spark at all 3 spark plugs. any suggestions?
Submitted: 7 months ago.
Category: Boat
Expert:  Charles replied 7 months ago.
Hello Jake, my name is***** will assist you.Do you have the serial number of the engine handy?
Customer: replied 7 months ago.
Hi Charles OR127491
Expert:  Charles replied 7 months ago.
Hello again Jake,first thing we need to look at is the fuse to make sure that it is still good, and then the kill switch. Cycle the switch a few times and then try to start the engine again to see if it will go.Let me know what you find out.
Customer: replied 7 months ago.
Charles, the fuse was blown in the yellow fuse block, already replaced it... Engine cranks but no spark. Engine is not equipped with a kill switch
Expert:  Charles replied 7 months ago.
Is this a remote set up or tiller?
Customer: replied 7 months ago.
Remote set up.
Expert:  Charles replied 7 months ago.
Do you not have a dead man switch near the helm on this set up?if not, there should be one on the front of the engine.
Customer: replied 7 months ago.
Nothing at the helm nothing, nothing at the engine. I followed the wiring diagram and the wires marked kill switch just terminate and are caped off... The only thing on the front of the engine is an oil warning light
Expert:  Charles replied 7 months ago.
Ok great. How did you test the engine for spark?Are you sure that you are getting fuel pressure?
Customer: replied 7 months ago.
I tested the old school way by grounding the spark plug to the engine block, doubted myself and borrowed an in line tester that goes from spark plug wire to plug and had a light... No spark. Tank is full, primming bulb stiff, fuel leak when I disconnected the quick connect to engine...
Expert:  Charles replied 7 months ago.
On your control box, is there not a switch on it that is red?Can you upload a pic of it here?
Customer: replied 7 months ago.
By control box you are referring to the throttle control ? If so, then no nothing there. Just a throttle with trim control
Expert:  Charles replied 7 months ago.
Any pics that you could post here?What boat do you have the engine on?
Customer: replied 7 months ago.
I'm not home to get the picture. When I get home what do you want the picture of specifically ? I've been around boats for the last 20 years, there's definitely not a kill switch at the helm. I think this is related to the ECU or ECM ( the box with the diagnostic port on it )on the engine, or other electronic related parts. Do you have some experience with this ?
Expert:  Charles replied 7 months ago.
I have a great deal of experience with this engine. I am a certified Mercury Outboard tech and work on them in real life. It is just odd that it fired for you, then after you stopped it, it would not restart. Do you have a multimeter also?
Customer: replied 7 months ago.
I have a multimeter
Expert:  Charles replied 7 months ago.
Ok, set it to a scale around 400V AC, unplug one of the coils. insert the red meter lead to the harness plug and the black meter lead to a good ground. Have a helper crank over the engine and see if you get a voltage reading.
Customer: replied 7 months ago.
I can give this a try, it might be as late as Monday , I'm traveling for work. Is that ok?
Expert:  Charles replied 7 months ago.
Yes, that is fine. There are no time limits here.

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