Alternator Short Near Fire

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…Melted Alternator wires…

There is nothing as frightening as an electrical fire onboard a boat at sea while underway! Nothing. This happened to us as we were heading to the Bahama Banks from Crab Cay via Grand Cay. Luckily, we have a procedure taught to us by Tom Tursi of The Maryland School of Sailing and Seamanship.  We check our engine room and bilges upon first starting and then check them every hour, yes, every hour, while we are running. This procedure just saved us from a full out electrical fire onboard.

When doing our first engine room check underway, by looking into the engine space, we saw sparks arcing from the back of the alternator! WHAT? SPARKS? OH NO. SHUT DOWN THE ENGINE NOW! This stopped the outflow of the amps being produced by the 120 amp alternator, but it did not stop the sparks and amps flowing FROM the 600 amp hour battery bank.

The positive post on the alternator was failing and it was shorting to the alternator case. This arcing and sparking was generating enough heat to melt the wiring harness and the wires attached to the alternator at the positive post.

To stop the electrical current flow, I had to drop the battery 1-2-All switch panel and then disconnect the positive wire connected to the alternator. Once this was disconnected, the alternator circuit was now open and the current and shorting stopped! WHEW, SAFE at last, NO FIRE. Close to a fire, but Tom Tursi engine room checks saved our boat once again! Now at this point, Sunday morning, we have no more alternator so we continued on with Wind and Solar for our electrical needs. Little did we know, it would be 5+ days without an alternator until we resolved this problem.

We sailed on and reached the Bahama Banks where we anchored all by ourselves in the middle of no where. The night was to be relatively calm with 10 knots of winds, but as usual, the winds came up to 20 knots and we spent our worst night on a boat we have ever had in 25 years! Cabinet doors were flying open, the boat was rolling side to side, deck to deck, and the bow was going up and down so much the anchor pulpit would hit the water. The anchor bridle was tugging at the bridle so hard, I thought it might break or rip the deck cleats out. We had 150 feet of chain out and our 55 lb ROCNA anchor and our windlass is broken. So, there was no way we could recover the anchor in these conditions by hand at night. It was too dangerous. We talked about it but decided we would need to wait until daybreak. The sun finally came up and we hauled the anchor in by hand and set sail for Fort Pierce, 62 nm miles away.

We arrived Fort Pierce by 1700 and headed directly to the anchorage where we popped a bottle of bubbly (it was Cava sailed from Spain by good friends, Ed and Sue) and celebrated our successful trip. That night, we crashed at 2000 and did not wake until 0700! Now, it was time to replace this alternator. We ordered a new Balmar, available the next day, and we walked the 1.5 miles to West Marine to pick it up. While there, I made all new wires and and a new wiring harness.

Of course, during this three day on-anchor repair job, it took us three trips to West Marine and one UBER car ($28 round trip) to NAPA for parts to complete the installation. The job seemed to take a lot more effort than expected because the new alternator has the positive post on the wrong side of the alternator. Guess what? When first installed, this positive post grounded out against the engine block, so it would have had a shorting problem as well. I needed to solve this!

After several calls to Balmar, we removed engine room insulation to give the alternator more pivot room and then we went to NAPA for three belts, one 1/2″ longer, one 1″ longer and one 1 1/2″ longer. The longer alternator belt allowed us to pivot the alternator more outboard, getting the positive post away from the engine block. The one inch belt would have been best, but it put the alternator case against the engine room box, so we had to use the extra 1/2″ belt. This only gives about 3/8″ clearance of the positive post off the engine block. If these two touch, we will have a short and the same problem all over again! Very frustrating situation. I need to add a rubber boot over this positive post for protection from this potential problem. Balmar needs to move this positive post to centerline or outboard.

Here is a photo of the new alternator with the post nearly touching the block as installed now.

When inspecting the old alternator, I originally thought the short happened due to the insulator breaking down under the positive wire connection. Later I discovered the break down was inside the alternator case and the positive post was shorting out against the case at the connection. Here you can see the old alternator positive post and all the erosion from the arcing. Overall, we are very lucky we caught this early, before we had a full out electrical fire. Thank you, Tom Tursi and the Maryland School for teaching us safety procedures at sea.

Here are a few more photos…..

We wheeled the new alternator home in a cooler

The Balmar Marine Alternator, 60 Series, 100 amp

Easy connections, but #1, the positive post, becomes a new problem!
This post is inboard and touches the engine block!

The mounting feet are different widths. I needed new bolts and new spacers.
Another dinghy trip to shore and another walk.

The beautiful mural at the Ace hardware store, Fort Pierce, Florida

Working out the new wiring and connecting the new alternator.

Installed….but we have a new problem. The positive post hits the block!
So, we bought a 1/2′ longer alternator belt and pivoted the alternator outboard.

This is the positive post and how close it is to the engine block!

New wiring to the Balmar regulator in the battery box.

This waterspout was an indication of the troubles to come!

Lucky for us, the sailing was great and our Gulf Stream crossing was calm. 15-20 knots beam reach

In conclusion, DO HOURLY ENGINE ROOM CHECKS and simply know your engine room. You will look in there 1,000 times and nothing will be wrong, but, when something is wrong, you will catch it early, before it becomes a big problem. This could have been a huge problem or even a disaster in only another hour or two!
They say, CRUISING is FIXING your boat in remote locations! How true, and this is NOT the way I want to recall cruising…..THIS IS the way I think of CRUISING…..ahhhhhhh!
Team Island Spirit enjoying a sail in the Abacos in beautiful Blue Water. Beautiful and it is why we do this!

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0 Replies to “Alternator Short Near Fire”

  1. Glad things worked out safely in the end. That is what counts.

    I had the same issue with my Balmar 160 A alternator. That close clearance really concerned me. I glued a piece of rubber weather striping on the engine block right next to where the post was and put a boot on the post.

  2. Hayden, you are absolutely correct that one can never be too careful when out in a sailboat, much less when offshore or making a long crossing. I was always, though a set hourly schedule would have been even better, opening up the engine compartment and checking on the Yanmar in my IP 35. I'd just see how things were looking, but I also had an infrared thermometer (what if the idiot light and buzzer failed?) and would check on the engine temp as well as the fan belt and all the hoses and connections. Would have preferred an engine water temp gauge. Glad all turned out OK for you guys.

  3. My combination of knowledge of electronics (learned through Amateur Radio) and boating leaves me able to say only three words:





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