1997 DA - What is this and why did it catch on fire?

[clubcairn]

Hello from the Bush River, MD, new owner of a 1997 330 Sundancer. 1200hrs 7.4L mercruisers (carbs), FWC, 630 V drives, survey and sea trial went very well. On stands for winter.

Been working on a few things in the bilge and noticed this burned wiring harness/loom/connector looking thing - what is it? looks like it melted long ago and did not cause the fire extinguisher (only 12" from it) to go off. Adjacent wiring melted too such as the starter wire.

The boat runs perfect, all gauges reading properly except fuel level. I believe only one light shines when testing the system monitor panel. Is this part of the system monitor?

The last pictures show its location on the port engine and how the starboard engine has one as well but it is not burned.

Thank you!

Thank you!

 

[Nater Potater]

I'm thinking someone really dodged a bullet at some point. I would be for carefully peeling back until you reached clean wire and spicing in some new sections. Fortunately, you have a good harness to model it after. It's possible this was caused by an electrical overload, so be aware that the damage may go farther than what you see here.

 

[bahamabreisus]

I am really surprised that was not caught in the survey. That's old damage, so was present at survey.

 

[Saverio]

almost looks like it was caused by heat. like maybe leaning against the exhaust.
That big plug you see is called a cannon plug. it the connection for the main harness to the engine.

 

[clubcairn]

Bahama, I agree. I’m getting to be fairly disappointed in the survey. Especially in the bilge. I think he was used to larger boats and didn’t really take my 330 seriously. He was done ($1200) in 3 hours.



Saverio, I was wondering that too - maybe the exhaust was run dry at some point and melted it. Although the starter wire is a bit far away. Just to clarify - when you say engine harness do you mean going to the engine sensors/ignition module? This being a carb motor does not seem to have too much going on for electrics.

I will unplug it and see if the connections are damaged and I’ll replace the starter cable.

is it true that these engines have 2 of every sensor ? I believed I’m seeing an oil pressure sender on each side of the block. And the left side one’s wire is burned too.

Hmmmm

 

[clubcairn]

I think this is the ignition system I have. Wow it looks like that cannon plug connects to a lot of things. I’ll see if I can locate a replacement harness.

just wish I knew what caused this

 

[Golfman25]

almost looks like it was caused by heat. like maybe leaning against the exhaust.
That big plug you see is called a cannon plug. it the connection for the main harness to the engine.

I’ll second the heat cause from the riser that is right there. Has that been changed? While it’s your boat now, maybe the previous owner can clear up the mystery.

 

[Lazy Daze]

That definitely looks like a "melt" from something else. Regardless, check the condition of the wires inside.

"Two sensors"... sort of. For example, yes, there are two things monitoring oil pressure - but one is a sensor and drives the alarm while the other is a sender and drives the gauge.

 

[Saverio]

that plug is used if you want to pull the motor. you dont have to cut anything or remove anything you just unplug it

 

[clubcairn]

Ok understood. I will take pictures of the inside of the plug when I’m back at the boat. With any luck I can just replace the loose wires and leave the cannon plug .

I imagine the exhaust manifolds can get as hot as automotive ones when there isn’t coolant/water flowing through them. Probably didn’t take long to melt things laying across it. Weird the other side shows no signs of anything melting

 

[Lazy Daze]

We're obviously grabbing at straws here trying to guess what happened, but a logical explanation could have been a blocked water intake (or strainer) or a failed impeller. Either of those would only affect one engine and cause it to get hot with no/little water flow.

The high temp alarm would have sounded well before it would haven gotten THAT hot to cause the damage so I think it would have had to run for a decent amount of time to cause that damage, though. Meaning, it may have been (remember, just guessing here) run with the alarm sounded for some time and/or the alarm wasn't (is it now?) working. Of course, the dash gauge would also indicate high temp.

"Alarm working" quick check... You should get an alarm when you first turn on the ignition (no need to start the engine) because at that point you won't have oil pressure.

 

[hughespat57]

I downloaded those photos on my PC so I could zoom in.
Very first thing to do is disconnect the battery to that engine. You start moving those crisp wires around and you could cause even more problems.
The fire system will not trigger until the heads reach over 175F for a period of time.

I'm not going to go with an exhaust/manifold over heat, many of these wires are to far away.

Looks like it started to burn low and spread up the loom and wrap burned off, the small wires look ok but all the tape burned off.

On the good engine there is a large gauge yellow wire? On the bad engine there is a yellow wire that looks smaller and burned off?

I would thoroughly check the engine ground cables and connections to the battery. When grounds go bad every other smaller negative wire will try to carry the cranking amps and quickly over heat. Did it start easily when it was sea trialed?

Looks like heat/flame came from bellow

 

[clubcairn]

Lazy, apologies, I meant other side as in the other manifold on that same engine.

No alarms before starting. Does the sound come from the system monitor panel?

Hughes, thank you for that analysis! I will trace where that yellow wire goes.

I will try to get a better viewing angle farther down below maybe we will see what started this.

Surprisingly, all my grounds appear very clean and free of corrosion, but I will remove them and clean with wire brush.

Started very quickly/eagerly even while cold on sea trial.

I appreciate all this insight. Even though it is running well I will not overlook this.

 

[hughespat57]

one final observation
The fuel pump is on this side of the engine near the pulley end (stern)
This line should be the fuel line.
It looks like it was recently repaired, very clean compared to the other parts.

A fuel fire would account for the from down low and all the damage appears to be from the outside of the cables.

I would be demanding a refund from that surveyor...

 

[clubcairn]

That is a brass adapter fitting going into either a pressure or temp sensor on the transmission cooler. Absolutely can see how you would think that it is fuel line though. The fuel line goes across the bell housing a little higher up. I really appreciate your insight.

Going to call my surveyor…

 

[QT1]

Hello from the Bush River, MD, new owner of a 1997 330 Sundancer. 1200hrs 7.4L mercruisers (carbs), FWC, 630 V drives, survey and sea trial went very well. On stands for winter.

Been working on a few things in the bilge and noticed this burned wiring harness/loom/connector looking thing - what is it? looks like it melted long ago and did not cause the fire extinguisher (only 12" from it) to go off. Adjacent wiring melted too such as the starter wire.

The boat runs perfect, all gauges reading properly except fuel level. I believe only one light shines when testing the system monitor panel. Is this part of the system monitor?

The last pictures show its location on the port engine and how the starboard engine has one as well but it is not burned.

Thank you!

View attachment 137848 View attachment 137849View attachment 137850 View attachment 137851 View attachment 137852 View attachment 137853 View attachment 137854

Thank you!

Where are you located on the Bush River?

 

[clubcairn]

Where are you located on the Bush River?

PM sent

 

[clubcairn]

I was over at the boat today (sorry forgot to take more pictures) and I looked farther down for what might have caused this fire. It definitely happened from pretty far down.

I saw the oil pan is rusty on the side where the fire happened which is very near the shaft seal. Is it possible the shaft seal got hot enough from friction to melt things in the area - possibly igniting the paint on the oil pan? I have heard these shaft seals are dripless but I admit I really don't understand them entirely. Is this being the cause completely impossible?

The only completely bare wire I found is going to the secondary oil pressure sensor. It seems all the other wiring still has jacketing so I will likely just be taping/shrink tubing everything up. The fiberglass stringer looks a little discolored and there seems to be some small spots of just bare fiberglass - not sure if this is a concern. I am sure pictures would be needed to tell. All hard though, no soft areas.

I checked out the fuel line that runs through were the fire happened and it seems to be ok. No fuel smell.

Also, my surveyor refuses any refund stating "if you wanted the engines surveyed you should have gotten an engine surveyor" Nice.

 

[Golfman25]

I was over at the boat today (sorry forgot to take more pictures) and I looked farther down for what might have caused this fire. It definitely happened from pretty far down.

I saw the oil pan is rusty on the side where the fire happened which is very near the shaft seal. Is it possible the shaft seal got hot enough from friction to melt things in the area - possibly igniting the paint on the oil pan? I have heard these shaft seals are dripless but I admit I really don't understand them entirely. Is this being the cause completely impossible?

The only completely bare wire I found is going to the secondary oil pressure sensor. It seems all the other wiring still has jacketing so I will likely just be taping/shrink tubing everything up. The fiberglass stringer looks a little discolored and there seems to be some small spots of just bare fiberglass - not sure if this is a concern. I am sure pictures would be needed to tell. All hard though, no soft areas.

I checked out the fuel line that runs through were the fire happened and it seems to be ok. No fuel smell.

Also, my surveyor refuses any refund stating "if you wanted the engines surveyed you should have gotten an engine surveyor" Nice.

But for the fact that's not an engine survey to pick up signs of a fire of some type, ok.

If it was your shaft seal, it would leak like nobody's business unless it was fixed.

 

[clubcairn]

But for the fact that's not an engine survey to pick up signs of a fire of some type, ok.

I'm sorry, I am not really understanding you here.

Ok so it probably was not the shaft seal. Neither of them leaked on the sea trial.

Side note - I am almost sure of this but do the shaft seal water hoses come from the extra port on the transmission coolers on the FWC 330s? I am replacing the coolers and will be swapping the old fittings over.