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Old 18-05-2022, 11:03   #1
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Alternator belt dust or unburnt diesel fuel?

Greeting forum users,

I'm finding a lot of black dust or soot in the engine compartment of my Catalina 42 (engine Yanmar 4JH3E). I've been told two stories; as the belt gets older it releases dust. Or the fuel filters need replacement &/or there is an air gap in the Raycor filter causing the engine to work harder and unused/unburnt fuel is turned into soot.

The boat will be launch for summer use later this month so I can't tell how the engine will perform just yet. I don't recall any sluggish issues last fall but my memory tends to be shorter than usual these days.

Can someone help me understand this issue better? (I will change the filters as a matter of due course).

Cheers
Wayne
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Old 18-05-2022, 11:12   #2
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Re: Alternator belt dust or unburnt diesel fuel?

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Originally Posted by Courageous View Post
Greeting forum users,

I'm finding a lot of black dust or soot in the engine compartment of my Catalina 42 (engine Yanmar 4JH3E) Or the fuel filters need replacement &/or there is an air gap in the Raycor filter causing the engine to work harder and unused/unburnt fuel is turned into soot.

OK, let's call BUNK to that one. Even if the engine were producing smoke (OK, call it soot) it would be coming out the exhaust, not depositing at the front of the engine.
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Old 18-05-2022, 11:26   #3
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Re: Alternator belt dust or unburnt diesel fuel?

belt dust. What amp alternator do you have?
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Old 18-05-2022, 11:29   #4
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Re: Alternator belt dust or unburnt diesel fuel?

I have same engine. It is almost certain to be belt dust.
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Old 18-05-2022, 12:16   #5
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Re: Alternator belt dust or unburnt diesel fuel?

yes, ok, belt dust.
probably naturally worn belt,
or wear accelerated by oxidation of the pulley groove,
or a slight misalignment of the pulley ...

how old is this belt?
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Old 18-05-2022, 15:00   #6
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Re: Alternator belt dust or unburnt diesel fuel?

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Originally Posted by Courageous View Post
...
...
1. as the belt gets older it releases dust.



2. Or the fuel filters need replacement &/or there is an air gap in the Raycor filter causing the engine to work harder and unused/unburnt fuel is turned into soot.

Wayne,


1. Could be. Why not just change the belt and assure that it is aligned properly.


2. Nonsense. Any air the fuel system would stop the engine.


Change the belt.


Good luck, nice boat.
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Old 18-05-2022, 16:43   #7
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Re: Alternator belt dust or unburnt diesel fuel?

Belt soot is a rare villain. Belt dressing spray is wonderful stuff to maintain belts.
Soot I’d suspect exhaust and be concerned.
I have a similar engine but I changed belts pulleys and installed a Bosch liquid cooled alternator. The broad belt is more stable than v belts. They all cook up with age
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Old 18-05-2022, 16:51   #8
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Re: Alternator belt dust or unburnt diesel fuel?

Take a look at the oil heat exchanger to see if there are any oil leaks. It could cook and soot here. Cooking engine oil or burnt fuel.
I have a CO2 detector for just such an event.
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Old 19-05-2022, 01:10   #9
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Re: Alternator belt dust or unburnt diesel fuel?

Quote:
Originally Posted by Rumrace View Post
Belt soot is a rare villain...
IMO, belt wear, producing soot, is a common villain.
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Old 19-05-2022, 02:01   #10
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Re: Alternator belt dust or unburnt diesel fuel?

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IMO, belt wear, producing soot, is a common villain.
A what age a serpintine belt on a boat is considered old and need replacing?
Cannot find that info anywhere…
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Old 19-05-2022, 03:37   #11
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Re: Alternator belt dust or unburnt diesel fuel?

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Originally Posted by CaptainRivet View Post
A what age a serpintine belt on a boat is considered old and need replacing?
Cannot find that info anywhere…
The ‘expected’ life of a serpentine belt may be anywhere from 4 years, to an entire decade, before you’ll need to replace your belt, depending upon engine hours [1,500 - 3,000 Hours], whether/not you have a self-tensioning device, and belt material/construction.

Belts made from ethylene propylene diene monomer (EPDM) tend to hold up much longer than those made from neoprene, a material used by older serpentine belt designs. Even when it’s not in use, the serpentine belt is still exposed to the atmosphere, and is degrading [mechanical wear, extreme heat, and contamination from oil and coolant, etc].

Wear on a single component is rarer, and more than likely a worn/misaligned mounting bracket, tensioner, idler or pulley, will cause [or contribute to] excessive belt wear, in addition to age.

The best strategy to gauge wear, is to inspect the belt for damage, and for proper tensioning at every oil change.

A failing or improperly tensioned serpentine belt usually exhibits some warning signs, prior to complete failure, including:
• The battery isn’t charging properly, or a battery or alternator warning is illuminated
• Engine overheats [water pump]
• Belt squeals, chirps or makes other noises [often this occurs during the first few seconds, after the engine is started, then the squealing may go away, or if it’s wetted by fluid leaks] [A quick, repeated chirp from the belt is usually more indicative of a belt pulley wheel that's misaligned (look for frayed edges on the belt as well)]
• Belt is shiny [glazed - especially at the edges], frayed, has chunks of rubber missing, has cracks between the belt teeth, or becomes ‘hardened’
• Belt gives off rubber dust

Make sure to inspect both sides of the belt, not just the smooth surface on top.

Naturally, the removal and replacement of any items, that a belt travels over, means the belt itself must also be removed first, in order gain access. So, when it's time to service/install a new water pump, or alternator, this is an ideal time to inspect applicable belts and pulleys, and replace as warranted.
Serious engine repairs, that require teardown [cylinder head gasket replacement, or front engine seals, etc] are also a common-sense opportunity to install new accessory belts, upon reassembly.
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Old 19-05-2022, 17:20   #12
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Re: Alternator REWINDING TO UP AMP OUTPUT

I was curious if one was to have a current 80 amp alternator re-winded to a higher amperage? Is this possible at all?
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Old 19-05-2022, 17:44   #13
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Re: Alternator belt dust or unburnt diesel fuel?

Any time you replace the belt or adjust the belt tension, you must replace the lock washer under the head of the bolt used to adjust tension or after a few hours of engine run time, the belt will loosen and create black rubber dust.
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Old 19-05-2022, 20:08   #14
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Re: Alternator belt dust or unburnt diesel fuel?

Serpentine belts get tiny cracks when glazed. Belt dressing spray extends their life, stop squeaks, lubricates the belt and pulleys.
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Old 20-05-2022, 04:27   #15
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Re: Alternator belt dust or unburnt diesel fuel?

I think you guys are missing another source and being misled by thinking there is one cause for the "black soot".
It is true that alternator belts produce a fair amount of fine black dust - mostly around the front part of the engine and surrounding area. It is not greasy or staining and wipes up fairly easily.

If you are seeing this all over the engine room then it is likely crankcase blow by. Here is a link to an article about it and a kit for correcting the issue. I have Cummins engines in my boat and do indeed have the appropriate model of this installed.

EnviroKit: https://www.sbmar.com/product/enviro...r-yanmar-4lha/

Blow by is not dust it is fine oil/fuel droplets atomized by the action of the pistons ans rings and escape the vent on the engine block. You can test the black by wiping it with your hand or rang and it will smear and not come up with a vacuum.

The trick is to collect it before it escapes and settles all over the engine room. It will combine with the alternator belt dust and make a greasy dust that will only partiall vacuum up.
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