50 AMP circuit breaker popping - Maxum Boat Owners Club

cuzins101 · 08-12-2013, 01:30 PM

1994 SR 1800 4.3L LX Mercruiser
The circuit breaker mounted on the engine is popping during start-up. The first time (2 weeks ago) I reset it and everything worked fine. This week I had to hold the CB in while starting the engine. The question is this, is the CB bad or is this an indication of a more serious issue? I have lost my confidence in the boat and don't want to strand the family for a third time!

pascavone · 08-12-2013, 01:58 PM

are you starting on one battery or both? only one battery per the mercruiser manual.

sounds like a short, so pull all the fuses out under the dash, and disconnect all the extra wires to the batteries, and then try to start the boat.

keep, installing the fuses, and running the boat until you have the breaker pop again to pin point the circuit.

ss3964spd · 08-12-2013, 02:58 PM

I don't think it's a short.

My guesses would be that either the breaker itself has gone bad - it happens, or the starter is drawing more AMPs than it normally should and is thus tripping the breaker (if the latter then the breaker is doing exactly what it should be doing). I would start by first replacing the breaker and checking/cleaning all battery cable connections, and if that doesn't do it then pull the starter and have it tested or replaced.

Dan

cuzins101 · 08-12-2013, 04:33 PM

It only has the one battery.
I just replaced the starter earlier in the year with the proper starter, but will check the draw with a meter.
I also just realized that the nav and anchor lights stopped working as well. So it looks like I have a day chasing wires ahead of me!

mmwjr · 08-12-2013, 05:34 PM

I agree with Dan here. Once running does the breaker trip? If not then not an issue with running power i.e. pulling helm fuses won't isolate issue. I don't recommend holding the breaker in because if there really is a fault it may result in melting the wiring.

BTY how are you planning to check the current draw of the starter? It pulls 100's of amps so a handheld meter will fry. Requires a meter rated for that much power.

cuzins101 · 08-12-2013, 06:03 PM

Mike- never looked into it so had no idea...

Once the engine is running, there doesn't seem to be any issues. If the starter was overdrawing, would it pop the CB every time I tried to start it? It seems to start at the house just fine when I Pre-trip test the boat.

edit- THANKS for the help!

mmwjr · 08-12-2013, 11:21 PM

If it was the starter I would expect it to happen every time. But (and I am stretching here) if the starter is cool at your house it may draw less current but still hot when you launch the boat.

Best I can offer is to replace the breaker and let us know what happens.

mike1 · 08-19-2013, 08:08 PM

Your problem is described as intermittent - this most likely means a fault somewhere in the circuit. Best advice is to seek professional service. Don't take chances if you don't know what you are doing. Doing so can turn a minor problem into a major one. Furthermore, don't circumvent the job of the breaker by trying to prevent its operation. It's tripping for a reason. Again, seek professional service!

cuzins101 · 08-26-2013, 03:39 PM

I replaced the circuit breaker this weekend and the engine started normally. The real test will be when I can get it back in the water for the day. The CB that I removed did not feel near as smooth and the new one when the reset button is pushed. I'll let you know the end result after "sea trials"...

cuzins101 · 09-03-2013, 02:00 PM

Sea trial failed and had to be towed in. Started fine at the house and ramp, started several times while pulling the tube. Once a wet tube and bodies came aboard the engine would not start. Dead in the water for over an hour! Got the boat back to the house and it started the first time

ss3964spd · 09-03-2013, 02:52 PM

Define "would not start". Do you mean the engine would not "crank" or "turn over"? Or do you mean the engine would crank/turn over but would not start running?

pascavone · 09-03-2013, 03:21 PM

the original circuit breaker was working correctly, as you do have a short.

It was telling you that, and your tossed it in the trash.

So, you have a short, or battery cable bare and rubbing on the engine block.

Again, disconnect every wire off the battery and pull all the fuses under the dash, and then go for a boat ride.

Run the engine only, wiring.

Keep installing back until you can repeat the problem.

cuzins101 · 09-11-2013, 01:29 PM

The CB is no longer popping after it was replaced. Going to go through the wiring and check for rubbing and loose connections and disconnect the fuse block (as recommended). I also checked the idle RPM's and plan to check the ignition timing and exhaust flappers.
I believe that either I have a short that only happens in the water or there is a back pressure issue. I did find a excessive dry-rot in the exhaust bellows...

mmwjr · 09-11-2013, 04:12 PM

Please define the current symptoms. Does the engine crank (turn over), spit/sputter, try to start, ...? Is it running at all?

It was running before and all you did was change the breaker, correct?

Back pressure makes no sense unless the dry bellows has collapsed shut, never see that happen usually tear off.

cuzins101 · 09-12-2013, 05:33 PM

Let's start from scratch...
Current symptoms: Starts on land with the muffs, while pumping the throttle. Brought to operating temp and restarted several times.
While in the water at the ramp starts.
After being anchored up (out drive either down or in trailer) the engine will turn over but not start. One time in the water it did eventually start, and ran fine all the way back to the ramp (about 20 min).

pascavone · 09-12-2013, 05:59 PM

I've have to take 80amp fusible link for $800 Alex.....

On top of your starter positive lug, is a 80amp fusible link. It's job is to hold back amp if you make the mistake of running on boat batteries.

It's power your engine and boat harness.

If it is pissed off, when it get hot, it breaks the circuit, to save you and your boat, until it melts.

So, bend your head upside down and backwards, to see what your looks like.

It's about $24 item, but this is the first fuses inline for power to your craft.

cuzins101 · 09-12-2013, 06:56 PM

I just replaced the starter and there was not one of these on it...
So, there is not one on it now. I take it, there should be one?

There is only one battery as well.

BTW, THANKS FOR ALL THE HELP SO FAR!

ss3964spd · 09-12-2013, 07:06 PM

If it turns over, but won't start, it isn't the fusable link - even if there was one.

Are you saying it won't start when on the water shortly after you shut it down, or it won't start on the water 30 minutes to an hour or more after you shut it down?

I think you're going to have to diagnose this on the water to truly replicate the conditions. It can only be one of two things; no spark or no fuel. When it decides to not start you'll have to veryify which of those two are not present. My guess at this point is spark. What ignition system is installed?

cuzins101 · 09-12-2013, 07:49 PM

I can smell the fuel with the engine bay open, and have witnessed the fuel spraying into the carb when trying to start.

Guessing the standard ignition system; distributor.

pascavone · 09-12-2013, 08:04 PM

I think your problem is heat related, not anything to do with the water the boat sitting in.

the positive battery lead turn the engine over, the wire on the fuse is only to feed power to the harnesses.

much like a car horn... (in the old days), they were directly powered off the battery.

also, the only other thing directly powered is the trim pump, as you can trailer up, with the battery switches off.