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Old 11-21-2016, 06:25 PM   #1
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Diagnosis (as in NY Times Mag)

I’m a fan of the New York Times column “Diagnosis”. The author posts mysterious medical symptoms online and invites anyone, doctors or laypeople, to make the diagnosis. When the column comes out, the first people to send in the correct diagnosis get credited. We’re anchored near highly regarded Ross Marine on the Sono River just south of Charleston, SC where we will be docking tomorrow and a mechanic will come aboard. First person to post here the diagnosis he makes will get an imaginary tee shirt.

Back in Albany, a few weeks ago, I went to start our starboard Perkins 6.354 and it would barely turn over. It acted like an engine with a very weak battery except that there was plenty of power according to the volt meters and the way the other engine lit right off with the two starting batteries connected. When the starter was engaged, the alarm light would dim to near invisibility. I went up to pick the two mechanic’s brains. One said it sounded like hydrolock from a leaking injector. The other said to check all the electrical connections because low voltage due to resistance in one could cause the starter motor to draw excessive current. I went back to the boat, opened up the engine hatch so I could watch the flywheel while starting, and tried again. The engine started right up. Later that day, I discovered that the terminals for one of the starting batteries were loose. The PO just set them on and forgot to tighten them. That was clearly the problem because a number of other electrical gremlins disappeared and the both engines started fine thereafter. These engine, BTW, despite their age start, as quickly as brand new engines – until a couple days ago.

The port engine is still fine. The starboard, contra-rotating engine (which also burns a lot more oil for some reason), wouldn’t start two mornings ago.

I had the two stating batteries (which are also house service on this old boat until I make some changes) hooked together with the “both” switch. It was early so 12V cabin lights were on. The engine barely turned over, like a car with a nearly dead battery. The cabin lights dimmed nearly to invisible and the alarm light on the panel went out. I checked the battery voltage, both were 13 volts. The other engine started normally. I fired up the generator and switched on the battery charger. Engaging the starter produced the same result. I opened up the machinery hatch and watched. The engine made two full revolutions slowly before I decided to stop straining the electrical system. No sign of hesitation at a specific point that might indicated a cylinder with fuel semi-hydro locking it.

Because of my previous experience, I decided to try again about half an hour later. This time the engine started easily and normally.

I decided that, because a waiting period after the problem seemed to work, I would test start the engine first thing in the morning so it could sit for a while during breakfast for another try. This morning, I did that and it started right up normally. We had breakfast and I went to start it to get the anchor up about half an hour later and it was back to acting like the starter engagement was creating a direct short. I watched the voltage meter and it dropped to 4-5 volts while the engine tried to start, turning about 1 RPM. I decided to proceed to Georgetown under one engine and find a mechanic.

Once out in the river, I tried the engine again and it started right up. We therefore proceeded here. After I shut down, I tried restarting the engine and it acts normally. We’ll see what happens in the morning. There is a good chance, of course, that I won’t be able to duplicate the problem for the mechanic. However, we must and will get to the bottom of it. Who wants to take a stab at getting the cyper tee shirt?
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Old 11-21-2016, 06:34 PM   #2
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I would start at the battery and again check all the connection for the starboard engine. Be sure to check at the batteries, the battery switches, and at the starter.
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Old 11-21-2016, 06:49 PM   #3
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Bum starter.
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Old 11-21-2016, 07:01 PM   #4
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Occam's razor-- it's usually the simplest thing.
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Old 11-21-2016, 07:15 PM   #5
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I'd have a digital volt-ohm meter out checking for voltage drop in cables and connections between the battery and the starter when it won't spin. That would give you something to work with...
No drop of voltage in the cables and decent battery voltage would indicate that the starter is suspect.
I used to get really annoyed when one of my employees "guessed" about a starting issue. It isn't all that difficult to diagnose.
There are lots of videos on YouTube on the subject if you need help.
Search for voltage drop test for starting issues.
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Old 11-21-2016, 07:25 PM   #6
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I'd have a digital volt-ohm meter out checking for voltage drop in cables and connections between the battery and the starter when it won't spin.
Not spinning is one thing. Can a voltage drop really cause a starter to suck all the current out of the whole DC system sufficiently to make the lights go out?
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Old 11-21-2016, 07:28 PM   #7
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Usually things that erratic are electrical.

Other than a total guess...just a few simple tests will show whether it is a hydrrolocking issue front water or fuel...or electrical.

A mech at Ross helped me with a water hydrrolocking 5 years ago and Ross allowed me to help for less than a couple hundred bucks.
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Old 11-21-2016, 07:42 PM   #8
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Not spinning is one thing. Can a voltage drop really cause a starter to suck all the current out of the whole DC system sufficiently to make the lights go out?
It depends. My point is only that you shouldn't simply guess. Once you have eliminated cables, connections and battery terminals you have to look hard at the starter or a condition like hydraulic lock that is making the starters job impossible.
Guessing leads to unnecessary expenses as often as not.
I've seen more than a few starters and alternators changed when the issue was a loose or dirty terminal...and it is so easy to avoid.
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Old 11-21-2016, 08:01 PM   #9
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Greetings,
Mr. RL. Mr. dh and the second mechanic make a valid point whereby all connections should be inspected for tightness AND corrosion. Personally, if you haven't already done so, I would remove the connections, clean them well (you can use a small wire brush or sandpaper, as appropriate), give them a coating of dielectric grease and make sure they are appropriately snug/tight. I would include both the high current (heavy battery/starter wire) and the low current (relatively) wires which would be the lighter gauge (smaller diameter wires) connected to the solenoid all the way to the starter switch. Might also be your starter switch.
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Old 11-21-2016, 08:19 PM   #10
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I agree that it's likely electrical. My guess is either the starter brushes are worn / hanging or the contacts in the starter solenoid are shot. If you have checked all electrical connections, did you check the crimps and are the conductors exposed, possibly corroded.

That was all one guess, right?

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Old 11-21-2016, 08:46 PM   #11
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Most likely electrical.

Take a good look at the grounds.

And measure the voltage at the batteries when you are having difficulty starting. You need to see how low the voltage drops under load. Not just what the voltage is as they sit there with no load on them.
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Old 11-21-2016, 08:55 PM   #12
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Don't forget to check the ground connection on the engine.
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Old 11-21-2016, 09:35 PM   #13
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Greetings,
Mr. HN. I saw what you did there. Tried to sneak in under the radar huh? Too late! Welcome aboard and good suggestion.
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Old 11-21-2016, 09:45 PM   #14
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Greetings,
Mr. HN. I saw what you did there. Tried to sneak in under the radar huh? Too late! Welcome aboard and good suggestion.

Good catch!

Welcome Hal.
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Old 11-21-2016, 10:17 PM   #15
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Don't forget to check the ground connection on the engine.




Took the words out of my mouth
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Old 11-22-2016, 12:19 AM   #16
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A properly executed voltage drop test on both the positive and negative sides has been very helpful in diagnosing electrical problems in my career as a mechanic. That's where I would start.
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Old 11-22-2016, 12:35 AM   #17
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Well since all the logical advice has been offered I can only tell you what my old salty dad would have said. "It has an intermittent in it, sometimes it works and sometimes it don't". LOL!
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Old 11-22-2016, 06:46 AM   #18
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Bum starter.
On our ex-trawler, we had a single Perkins 6.354 and it came with a spare starter. With twin 6.354's, the argument for a spare starter is even more compelling.

Don't disagree with the others on checking out all the wiring and connections but I would also check the stop/start solenoid (might be just a stop solenoid). Could it have been stuck in the kill engine position?

Oh, and don't forget to check your bank account. Be sure the checkbook is loaded. Hey, I can't be wrong with that diagnosis!
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Old 11-22-2016, 07:08 AM   #19
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Ignition solenoid.
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Old 11-22-2016, 07:54 AM   #20
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Quote:
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It was early so 12V cabin lights were on. The engine barely turned over, like a car with a nearly dead battery. The cabin lights dimmed nearly to invisible and the alarm light on the panel went out. I checked the battery voltage, both were 13 volts. The other engine started normally. I fired up the generator and switched on the battery charger. Engaging the starter produced the same result.
The above suggests the batteries were at 13V in the morning with no source of external charge. Unlikely, and that doesn't tell us anything about the batteries real state or their ability to support a somewhat heavy load.

I'd want to know the age of the batteries and their condition via SG and possibly a load test, not voltage.
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