Blown Electronics on 4Winns/OMC Cobra:

[Offrddrver]

Boat: 1992 Four Winns, OMC Cobra, 5.0 Ford motor.
ISSUE: At random the main 50 AMP contact trips, causing blown electronics.

Secondary issue: When the 50 AMP contact trips I usually lose an electronic component. Example: 1st Fish finder, 2nd High speed depth finder, 3rd stereo amplifier, 4th stereo deck. Nothing left to blow at this point.

Confusing part: In ALL CASES the component factory provided fuses were installed, and in ALL CASES the factory component fuses DID NOT blow even though the component DIED!

Testing: All CLYMER and SELOC electronic tests have been completed per the manuals and all of the tests are passing.

One thought is that there is a short in the alternator ONLY AFTER it is on an extended run (heat related), but I have no real way to find this. I brought the alternator to two shops that can Test Marine alternators, and both said the alternator was GOOD.

Has anyone experienced this in the past? If so, please give me your 2c or repair that fixed the issue.
Does anyone know boat electronics well enough to take an EDUCATED guess at troubleshooting this issue?
Please don't reply if you are just guessing and typing at the same time. Not trying to be rude, but I want a real troubleshooting path not hip shot!

Thanks in advance,

Offrddrver

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

How is the alternator wired? Is it wired to the starter lug? Is everything that died wired after the 50Amp breaker or do they still receive power even though the breaker blows? What is the voltage of the alternator output before and after the breaker blows? Do you have one battery or do you have things wired seperately on a house battery?

The reason I am asking these questions is I am wondering if the alternator somehow is wired so that when the 50Amp breaker goes, the alternator stops having a load on it and goes overvoltage on you.

I am definitely not sure why you are blowing the 50A breaker in the first place. Not enough info to even attempt to guess on that one.

Check any wiring that travels near the exhaust pipes. Although they are water cooled, they can get quite hot and melt through insulation.

 

[RickJ6956]

Re: Blown Electronics on 4Winns/OMC Cobra:

Trace every wire associated with the ground. A loose ground can cause all kinds of strange issues, including ESD (static electricity).

A couple hundred thousand volts of ESD won't blow a device's fuse because the current isn't high enough. But it will certainly take out the electronics.

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

Trace every wire associated with the ground. A loose ground can cause all kinds of strange issues, including ESD (static electricity).

You don't get ESD from a loose ground. Since the OP is a semi engineer, he is also going to realize that.

 

[RickJ6956]

Re: Blown Electronics on 4Winns/OMC Cobra:

You don't get ESD from a loose ground.

You make it sound like a disease. Ground strap and anti-static mat manufacturers all over the world are not going to be happy to hear that.

I won't argue with you, though. The OP can check the grounds ... or not.

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

You make it sound like a disease. Ground strap and anti-static mat manufacturers all over the world are not going to be happy to hear that.

I won't argue with you, though. The OP can check the grounds ... or not.

That's fine for grounding you. You need it. But unlike you the device isn't walking across carpet and rubbing against polyester to develop a high voltage surface charge. The are other reasons as well. If this was an issue, every stereo and radio sitting on a shelf in a store is in major danger of ESD which isn't the case. See many of these sitting in electrostatic bags?

 

[Offrddrver]

Re: Blown Electronics on 4Winns/OMC Cobra:

Bruce58,

Just to note....the entire wire system on this boat is factory, so hopefully that is a good thing as I have not seen posts for issues with this year or model of boat.

Prior to the ALT check, no electronics have been removed, other than the blown ones. So all wires were factory attached. There are no noted loose lugs that I can find yet.

Wiring: Bat to 1st 50A CB IN, Out splits to Start assist Sol and to the 2nd 50A CB IN, Out splits to Main harness and to ALT POS post. ALT GROUND is direct to back of block where it splits to BAT, Main Harn, ESA Mod, Trim, etc... ALT AC out direct to Choke. ALT EX Jumps to ALT S, connects/splits to Main harness, ESA mod, Coil +, & assist solenoid.

No, the start assist solenoid is between the 1st 50A CB and the starter, so the ALT and STARTER are not connected direct.

When the 2nd 50A CB trips it is lights out on the entire boat other than the trim. The TRIM circuit is the only circuit on 50A CB1.

I have dual batteries, but on a heavy duty three way switch. Either battery can run the entire circuit, but I've always run on BAT 1 and used BAT 2 as the backup. In short, I never run with the switch in the "BOTH" setting. Either 1 or 2 only.

I want to say the ALT is putting out ~14 volts or slightly more, but I will have to measure again next time I'm out. I don't really recall for sure. The company that tested the ALT has a great rep in the PHX area and he said the output/charge is all within spec for this unit.

I agree on your load theory as the boat/electronics are ALL GOOD one split second, the CB trips, and the next split second a component is DEAD! The boat motor still runs until I ease up on the throttle. When the RPM drops off the boat goes 100% quiet. At that point I know the CB tripped without even looking at it.
This happens totally at random. Other note, no two devices died at the same time. Just couldn't narrow it down in time to save other components.

All main power cables and wire harness are clear of the headers, and the harness on the top of the motor is in a "lifting" bracket I suspect to avoid the heat. I keep looking for other pinch points, or bare wires, but no luck yet.

I did pull the main harness plug and put a light squeeze on all female wire ends and reconnected. So far no additional CB trips, but no real long days on the lake yet either.

I did get a new battery as one was low volts and a little low on fluid/acid.

I'll keep looking.

Offrddrver (Off Road Driver)

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

I drew out the circuit and it is really apparent that when the second CB blows, there is no longer a battery load on the alternator and the output of the alternator is now only feeding the harness which may explain the blown devices.

My suggestion is to find a factory wiring diagram to find out if the output of the alternator is really in the correct place. Sure seems like it should be tied to the input of CB1 which in turn is tied directly to the battery.

I know this doesn't address the reason the CB blows in the first place but it is one of your 2 problems.

 

[Offrddrver]

Re: Blown Electronics on 4Winns/OMC Cobra:

I agree and had the same thoughts on the battery and CB setup.

However, it is the factory setup for 1992 5.0L & 5.8L Ford engine w/cobra drive.

I notice in the manual it show the 1993 battery goes to the started then the assist solenoid, then back to the starter, but the CB setup would still cut out all battery load from the alternator. (Not to get off track, as mine is the same as the 1992 schematic.)

Without the battery in the circuit, IF CB2 blows, I suspect the regulator on the alternator ramps to max voltage to try and compensate for the 0.0volts from the disconnected battery. However, the regulator was noted good, so it should have a REGULATED max.

I supose I could replace the regulator for starts, but like you said, it is a shot in the dark on why the CB2 trips in the first place. It is so random that I don't know how I would ever solve this problem.

In any case, thanks for the thoughts, feedback. Sorry it took so long to reply again, just a hell week at work, so this hit the back burner.

Have a good one, I'll post more if I find something. Always searching.

Regards,

Offrddrver

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

However, the regulator was noted good, so it should have a REGULATED max.

They don't. They can spike up. They have a sense voltage they are looking for so will spike up without a load.

 

[msargius]

Re: Blown Electronics on 4Winns/OMC Cobra:

No two electronics die in the same time, because only one need to absorb the power surge that is happening. I also beleive that this happen before the circuit breaker is breaking. Because of the capacitors and internal batteries there is a delay for the electronics to switch off. That is why you might think that the electronics blew after the circuit breaker. My guess is you are getting somehow a very high surge that trips the circuit breaker. Sometimes faulty circuit breaker can trip for no apparent reasons and need to be changed. You can also check the load on the circuit breaker using electrician style Amp reader...you clamp around the positive wire of whatever you trying to read... I would do the test at the circuit breaker, during a full power everything on... It will tell you the complete load that is passing by it.

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

Because of the capacitors and internal batteries there is a delay for the electronics to switch off.

Please explain to me what electronic devices have internal batteries in them and why that would make any difference? Also, don't you think that capacitors would actually help suppress a large voltage surge. As an electrical engineer, I would love to hear your answers.

 

[msargius]

Re: Blown Electronics on 4Winns/OMC Cobra:

Please explain to me what electronic devices have internal batteries in them and why that would make any difference? Also, don't you think that capacitors would actually help suppress a large voltage surge. As an electrical engineer, I would love to hear your answers.

If capacitors on equipment are sufficeint to supress large voltage surges, we will not need to use surge protection for computers , tvs, etc... Working in computer rooms for long time .. I have seen computers fried by surges.

Some equipments do have internal batteries...I am not sure about the marine ones...

what I was explaining why sometimes we see a delay when switching off equipment and that can be indicated sometimes by the slow dimming effect on the light panel on them. If his circuit breaker tripped than why the high current is still advancing to his equipment to damage it?

I will still not compete with an electrical engineer

 

[Juniinc]

Re: Blown Electronics on 4Winns/OMC Cobra:

a couple of things happening here,,,
either your starter is drawing way too much power,,, u do have a 50amp fuse before the starter? rite.
I would try to crank the starter / feel how hot they get(wire/starter).
maybe its a randomly short with ground, possibly some wires rubbing whenever it wants to,,,starter solenoid can be shorted internally.

 

[bruceb58]

Re: Blown Electronics on 4Winns/OMC Cobra:

u do have a 50amp fuse before the starter? rite.

There is never a fuse inline with a starter.