Alternator belt dust or unburnt diesel fuel?

[Finalee]

Try a heavy duty Dayco belt that's green. See if it all turns green.

[Courageous]

Thanks for all of your comments, the belt probably has 200 or so hours running time. I did tighten it this spring as a part of getting the boat ready to launch. I believe the alternator is 80 amp. Most of the dust is in the front of the engine compartment and it takes a fair bit of effort to wipe it down especially on the fiberglass motor mounts.

I will check out the link out for the Envirokit.

Thanks again

Cheers

[Rumrace]

I agree with Squanderbucks 100%.
Crankcase blow bye. You can get valve guide blow bye Piston ring blow bye but neither would put carbon in the air just the exhaust. Crank case over pressurized will expel soot.

[kapnd]

Not all “blowby” is necessarily a product of ring or valve guide leaks. Many motors will expel oil vapors when overfilled, or when running in rough conditions, or the boat is riding in an unusually bow high or low attitude.
Overfilling the oil sump is a common mistake that makes engine rooms dirty.

[bouncycastle]

Often aged battery demands more amps from alternator and loose or misaligned belt or worse rust on pully wheels will shread a belt in few hours running and cover engine room in black dust .Been there got the T shirt . A two mm misalignment and rust on pullies on old engine and larger than normal 80 amp alternator rather than Yanmar 35 or 55 amp did this to me very quickly .I sorted it and belt has run more than 100 hours so far .
if electric demands are high such as night time with Radar and radio light etc the alternator can drag a lot on single V type belt. For that abuse double V belts or better still flat serpentine belts are the solution
The standard Yanmar 55 amp alternator is often a joke to use on most cruising sail boats that remain at sea for days on anchor or sailing .The alternator is suited for motor boats doing day saiiling of a few hours with motor on all the time and battery hooked into shore supply from marina .
Any other use than than that marine type alternator hop ups big bucks and serpentine belts combined with solar power and large battery banks become the big bucks norm

About 23 amps of power or 250 watts from alternator equals one HP of engine power to give this 250 watts

A cruising boat that sails all day with the typical 2 lead acid battery domestic type deep cycle of 100 amps each depleted will need a typical marine alternator type of 100 amps a few hours of engine running to put in 200 amps at half gas like 2000 rpm or s lot more hours at low gas of 1000 rpm and forever to recharge at tick over of 800 RPM

The better tyoe 100 amp marine alternators at 2000 rpm will make typically 50 amps changing for first hour to two hours and charging rate will drop down as battery charges up and alternator heats up and drops charging rates
The single V Belt will have 2 HP of drag on it for some time and will probably shread up fairly guickly from this use as belt heats up . The single V belt can really only take the drag of 10 amps for short times less than one hour.
The stone age alternator that Yanmar uses typically 35 pr 55 amp drop to less than 5 amps charging after 15 minutes and takes forever to recharge a empty domestic battery bank . This protects single V belt from shreading from belt drag but wears out belt from long engine hour use to recharge battery.

For battery recharging the use of the diesel inboard is not clever for live aboard boats but can work for weekender sailors going from Marina to marine in short cruising hops .

More use full info can be to say type of alternator you have and is it single belt and size of starter battery and domestic battery and are they on solar or shore power and are batteries very old or exposed to extreme cold or worse extreme heat.

hope that can help

[bil56]

@bouncycastle
great, I couldn't have said it better!

[Courageous]

thanks again for your comments, I really appreciate it.

Cheers
Wayne

[capblasters]

I can think of one other cause - debris from worn engine mounts. It would accompanied by changes in vibration felt in the hull. Engine mounts usually last 1200 hours - check the service manual.

[JBsurfin]

Originally Posted by Courageous

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

I say belt dust, on my Perkins its a quick indicator to replace when I see the build up start. Make sure you have the proper belt and tension to cut down wear.

[MJH]

Originally Posted by Courageous

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

I suspect it is belt dust. A Google search shows that engine model having a standard belt versus a serpentine belt which are better performers. An upgrade to serpentine is possible and I recommend it.

[nofacey]

Most likely belt dust, especially if there is a ring of it that lines up with belt. Usually more prominent where the belt turns a sharp corner. Change belt, check alignment, roughness on pulleys.

Or it could be crankcase blow by, more common with higher hour engines. Check that crankcase vent is in one piece & connected to air intake……and if you haven’t changed the oil recently, get to it. Oily Deposit more concentrated around the ends of the crankcase vent line.

Or, it could be a slightly loose exhaust manifold - deposit concentrated at exhaust connection to block. Try snuggling up the manifold bolts.
- Have seen this particularly where a manifold bolt has broken.

[skipgundlach]

My vote is for belt dust.

That said, the belts in my boat's residue pattern were like toner cartridge stuff.

If you don't vacuum it up, you'll smear it, and make life much more difficult.

That said, Tilex spray does a very nice job of picking it up while you're cleaning whatever surface was affected, using paper towels.

It took me some time to figure out that I could vacuum most of it without the smears; doing so before it's no longer just dust, especially in small, not/flat places, will keep the area much cleaner.

From conversation I impute that it's a serpentine belt, which is different than mine, a vee.

For other readers, if you have steel/iron pulleys, and don't use the engine regularly, they'll rust. After a long layup, removing that rust before firing up will do a great deal to minimize rust.

For our main pulley, I used a file set to cut in the rotation direction, and dressed that pulley by briefly running the engine (our RW pump was belt driven, so I limited the time of running until the engine was warm to the touch). The FW pulley, and the alternator pulley, I turned by hand in order to do the filing.

WRT blowby, we have a filter set up with a hose to the valve cover stem; the filter induces a small vacuum (be careful not to exceed the back pressure or you could starve your seals), which causes any blowby to be consumed as fuel (diesel, of course, example).

YMMV, of course!

[SohoSail]

Same engine as you.

"For other readers, if you have steel/iron pulleys, and don't use the engine regularly, they'll rust. After a long layup, removing that rust before firing up will do a great deal to minimize dust."

This was my issue mostly, and the belt dust was clearly in a location that it came off the belt. I check belt tension frequently and tidied up my pulleys and dust disappeared. Also went to Gates XL HD belts, green ones, much better.

[Rumrace]

Belt dressing sprays a goo on belts which protects and reduces belt dust. Belts often distribute oil and dirt and are not the source. Many sailboats don’t have proper air circulation poor intakes and get run like generators rather than lawn mowers.
There are zero reasons to have a dirty car engine and no reason but an oil leak on a boat for the engine room to collect any dirt. Only time a belt puts out a lot of rubber is when it’s shot or a worn pulley is tearing it up. Belt dressing extends pulley lift also