Engine circuit breaker tripping

[tgebler]

I have 454 Mercruiser engines with fuel injection. The starboard engine would not start and I learned of the engine circuit breaker which is located right below the distributor. I pushed it once and the engine started, Since then, the engine stops running, I push the breaker and it starts.

Any idea why it keeps tripping? Thanks.

[km1125]

When does it happen? How often has it happened so far?

Could just be a bad breaker. I think my first step would be to swap it with the other engine and see if the problem moves to that one.

[Viper]

You could have a wiring issue but it's not uncommon for those breakers to fail.

[tgebler]

I should have noted that this issue began after I replaced the battery for the starboard engine. Initially the engine started as normal after the battery swap but then stopped after a short trip. I had to reset the breaker twice to get back to the dock. The Admiral was not happy!

[Viper]

I trust the replacement battery was new and fully charged? Check you connections to ensure they are clean and tight.

[km1125]

Yep. Go back to the scene of the crime and doublecheck everything you touched (and even some you didn't intentionally touch, but might have in the process!).

[tgebler]

Update. I replaced the engine breaker and it appeared to fix the problem. Tried to start the engine yesterday but I am having the same problem again. I did not try to push the new breaker to start the engine. I am assuming I have a short somewhere. Where do I start?

[bud37]

Update. I replaced the engine breaker and it appeared to fix the problem. Tried to start the engine yesterday but I am having the same problem again. I did not try to push the new breaker to start the engine. I am assuming I have a short somewhere. Where do I start?

So when you say tried to start, does that mean the engine turned over but refused to start and at some point popped the breaker back out ??

Or was the engine just dead as if it were still in gear when you tried to start it ? If so check the neutral switch circuit.

Unfortunately if that breaker is going off at odd times you may have a short, in that case you will have to go thru all the wiring with a bright light and fingers to check for any bad grounding, worn thru insulation making contact with the engine, especially the start circuits...... , etc etc.

Really tough to guess when not there with eyes on. Good luck, I hope you find the problem soon.

[tgebler]

So, I looked for a short which is tripping the breaker but I am not sure what exactly I am looking for. Can someone tell me EXACTLY how to perform this task.

By the way, I notice my engine room light also do not work even after the bulbs were changed? Any relation between these two issues other than they are electrical?

Thanks for any thoughts you may have.

[km1125]

Doubt the lights in the engine room are related. They'd be on a completely different circuit.

As to what's tripping the breaker, that can be a real challenge, especially on an intermittent issue. First is a good visual check of the connectors and wiring to see if anything is intermittently grounding due to proximity (connector getting too close to something) or some compromised insulation on a wire that's allowing it to short to a ground nearby.

If it's more predictable, like it happens at specific times (like right when you turn the key on) then you can be more methodical to narrowing it down. One thing you can do to help identify this is by determining exactly WHEN it trips. Periodically test the breaker to see if it's tripped BEFORE you try and start the motors and at different times in your sequence of usage. If you can narrow down WHEN it trip to certain times, then you can start looking at what is actually being powered at that time.