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mercmastertech, Service Manager, Master technician
Category: Boat
Satisfied Customers: 249
Experience:  Service Manager, Master Mercruiser, Master OMC Cobra and Certified Volvo Penta Technician
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I removed my battery from MerCruiser 3.0 earlier today, to

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I removed my battery from MerCruiser 3.0 earlier today, to give it a good charge. I just reinstalled in, here in lies my dilema. I connected the negative to positive, and positive to negative and when I saw the sparks fly, and realized the stupid, dumb thing that I just did, I undid my mistake, and connected the battery correctly.

My problem is that it won't turn over, no click, nothing.. I can't reset the 50A circuit breaker, the red push button switch won't stay reset. So, I removed the circuit breaker and both lines going in/out of the circuit breaker. I connected these two lines together to troubleshoot my situation to see if the starter motor would fire up. It did not.

So, can you help with what I may have fried? The starter solenoid? Or is there another fuse that I may have overlooked?

All other electrical works fine, lights, horn, bilge pump, trim, etc.

1997 Bayliner Capri 1850LS Bowrider, MerCruiser 3.0L 135HP, Alpha One I/O.

Thanks again,
Steve Brandon

Hello Steve,


No worries, this happens more often than you might think.


If you look at your starter, you will likely see a square 90 amp fuse mounted to the starter solenoid (some 3.0L engines used a square 55 amp fuse). Check for voltage on both sides of this 90 amp fuse, if you do not have battery voltage on both sides of the fuse, then the fuse is blown and will need to be replaced (it is usually the first thing to blow if a battery is hooked up backwards).

Here is a reference picture of the 90 amp fuse at the starter (item #8)....




If the 50 amp breaker will not reset after replacing the 90 amp fuse (assuming the 90 amp fuse is blown), it may be damaged and you'll likely have to replace the breaker as well.

I will also attach a general wiring diagram of a 3.0L engine for reference should you need it....





If I have helped with your question, please click "accept", thank you.


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