motor wiring meltdown

J

Jimbo

New member
I just uploaded 5 pix of what you don't want happening to your engine.
We were heading up to our cabin, in the rain, with our slant back on.
As we pulled into our dock, the engine stalled and "low voltage 9.6" came up on the chartplotter.
I tried but the engine wouldn't even turn over.
I went out and pulled the slant back open to see smoke pouring out of the engine cowl.
I shut the battery switches off and checked for any actual fire.
I managed to get the kicker started and get into the dock.
I then pulled the cowl off and had a look.
As you can see, major wire meltdown around the starter and alternator.
Now, what I had done different than normal when running of the boat.
I put a 1750 watt invertor in 2 years ago, never used it much but came up with a great idea to run a little ceramic heater in the cabin during the fall and winter while under way. I set it on 750 watt when we left the marina, Sher actually took a coat off during the trip, which in Jan. was amazing.
The invertor is connected to just my 2 house batteries with a off/1 Perko switch at the batteries.
For the electricians in the house, a roll of 2/0 welding cable got delivered to one of our job sites along with rest of our order a few years ago so I used that to wire the inverter. Voltage drop due to wire size was not the issue.

When we got home, I charged up the house batteries and then did a load check and have found one battery dies as soon as a load is put on it.
My mechanic thinks the bad battery, along with the heater load, caused the meltdown.
We have ordered new wiring harness's but won't know until we get some voltage onto the motor to know whether or not we cooked the main processor.
Ahh the joys.......
Any thoughts??????
One last comment, the trip up to the cabin running the 115 takes about 35 mins.
Trip back to the marina on 15 HP kicker....2.5 hours.
Tnx, Jimbo
 
My guess is a short. Yes the load is more than the alternator (or equivilant) can put out--and this may cause some heat in the wiring--but you are looking at 30 or so amps (don't know the charging rate of your new motor)--but what you are showing in the photos is like a dead short in the 12 volt system. If the motor ran to get you to the dock--the processor is probably OK.

This does bring up a very good point--and it involves the reason to have the voltage sensitative relays. If one battery goes bad, then it will be isolated if you have VSRs.

The other point--is that I see folks running toasters, coffee pots, heaters etc off inverters and relitatively small battery sets. This can be a recipe for diseaster. Yes I have an inverter--and I use it for 5 minutes of microwave use--that is about it. I have had bigger boats where I ran a household Refrigerator--and currently an RV with huge battery banks and I run TV and sterio for a few hours. But these were engineered systems--with fan coolers on the inverters, over and under voltage relays etc. So I wonder if sometimes we tend to under engineer our systems because we can and it is convient? (I could be just as guilty with a lower level inverter in my Tom Cat--but I know its limits.) Not implying that this incident was due to the inverter and heater, because it may not be--and I don't think so looking at the wiring photos--but I don't have all of the story as how the motor was hooked up to the batteries and inverter.

I would trace out the circuits and check for a short to be sure that you don't hook up a harness and have it happen again (also a short would blow the battery)
 
I see your power cabling wasn't marine grade conductors. I wonder if the resistance didn't build up over time due to corrosion and finally went over the edge with the increased load. It would be interesting to know how long it took to reach the condition in your pictures. Was it fast due to a short or was it slower due to load and corroded wire or lugs? Maybe the corroded wire or lugs heated up and partially melted the insulation on a section of the wire which then went to ground and shorted out.
 
If the starter gear stayed engaged while the motor was running, the starter becomes a generator and can result in this meltdown. Be sure to lube the starter shaft/gear occasionally.
Roger
 
Holy short circuit Batman! :cry

You are extremely lucky that a fire didn't ensue! Let us know how the repair goes, looks like it's pretty extensive. Good thing it happened at the beginning of the season and not in the middle!

Glad you are all OK.

Charlie
 
Thank goodness you had no fumes nearby!

My old fashioned, conservative take on inverters and high amp 12 Volt usage is that a boater is usually better off to learn to live on the water with less electricity.

I have a tiny Cobb grill that can cook or heat for hours on 8-10 briquettes, and other means of heat and cooking such as butane, LP gass (small) etc., and a 110V / 12 V plate cooler that I run off dock power to save the ice and live with ice only while cruising.

A person can get along just fine drinking ambient temperature water and ppl do not need soda pop to live. I know Pat and some others have a specially modified drink pyramid for survival, though...

I hope the damage did not get deep into expensive engine parts for you!

Thanks for posting,

John
 
Forrest's comment is very important and woth emphasizing for some of the newer boaters. The most common cause of fires on boats is corrosion at the 110/220 plug going into the boat. This has corrosion, arcs, carbon builds up and resistance increases. With increased resistance, there is more current flow and then more heat until the insullation is melted. Obviously this instance is a 12 volt circuit--but the same principles apply.

In the boat these fittngs can be at battery terminals, where there is a high flow to begin with.

It will be interesting to see what is found out as the cause.
 
forrest
Not sure what you mean when you say marine grade wiring.
The only cables that actually broke drown and shorted were the positive and negative cables leaving the actual motor which were in a moulded jacket with the ignition wiring
Other cables that I had ty wrapped to these got hot enough to start to melt the outer insulation but they didn't actually breakdown.
Once I got the boat home I isolated those 2 wires and and was able to use my onboard charger to charge up my batteries before doing a load test.

rogerar
My mechanic and I talked about the starter turning into a generator issue but he said that before the starter could generate enough amperage to do any damage, it would self destruct internally.
He has had this happen on a couple of starters that he has had to replace.

Talking about anything flammable being around, if you look at the picture with the melted boot, the grey line you see is my fuel line... they were all nicely ty wrapped together. Wonder what the flame test max is for these types of hoses

Appreciate all the comments
Tnx, Jimbo
 
It's not easy to see, but it looks like the ground cable has the most damage, and that damage is near the connection to the block. If that connection was loose, and heated up, the aluminum block would heat up in that area, further loosening the connection.

Outboard motor alternators are not designed to supply continuous maximum output. They are designed to run a normal load such as radios, lights, etc., and to recharge the battery. Subjecting the alternator to a high load over time could cause overheating of connections. A bad battery could cause the same thing.

When I was repairing OB motors, I found many with a loose connection where the battery cable attaches to the starter solenoid. As a part of servicing the motor I checked the tightness of that connection. Also check the ground cable connection on the block. The other most common place to find a loose connection is at the battery. Wing nuts should be replaced with regular nuts, and tightened with a wrench. The wrench MUST be too short to reach both battery terminals at the same time. The wrench should then be stored where handy so that in an emergency, the battery cable can be disconnected. THROW AWAY THE WING NUTS.

Larry H
Retired outboard mechanic.
 
Back
Top