Ask Sail: Soot or Something Else?

There is a soot-like buildup on the face of the alternator on my diesel engine. I have not noticed any fumes or exhaust leakage in the engine compartment.
Author:
Publish date:

SOOT, OR SOMETHING ELSE?

There is a soot-like buildup on the face of the alternator on my diesel engine. I have not noticed any fumes or exhaust leakage in the engine compartment. What are your thoughts or comments on what it might be?
Mike Asbury, Dandridge, TN

Nigel Calder is an author and expert on boat systems and diesel engines

Nigel Calder is an author and expert on boat systems and diesel engines

Nigel Calder Replies

This is most likely very fine belt dust from accelerated belt wear. There are three likely causes: the belt is a little loose and is slipping under load (mostly right after the engine starts when the alternator goes to full power); the pulleys are worn so the belt is bottoming out in the pulley grooves (belt loads should be transmitted through the sides of a belt, not through its base); or the pulleys are misaligned. If your pulleys are rusty, this will also accelerate wear. The most likely cause is that the belt is a little loose and is slipping when the alternator is at high levels of output. This will cause the belt to get hot and become hard and “glazed” over time. If you look closely you will see hairline cracks running from the center of the belt toward its perimeter. Quite often, a slipping belt will also squeal, sometimes just momentarily after the engine is cranked. When checking belt tension you should not be able to depress the longest stretch of belt more than 3/8 to 1/2in with quite a bit of finger pressure.

Related

shutterstock_543237994

The Slow Route to Cabo

Each November, cruising boats start leaving California for “a winter of fun in the sun down Mexico way.” And having spent the summer and autumn on a leisurely passage down the West Coast on board Distant Drummer, our Liberty 458 sloop, my husband, Neil, and I were now in San ...read more

MHS-GMR_3549

New Multihulls 2018

Farrier F-22 New Zealander Ian Farrier ushered in a new genre of sailing with his folding-ama trailerable trimarans, the best-known of which are the Corsair designs. Farrier’s last project before he passed away last year was this sweet little tri. Available in three versions, ...read more

shutterstock_373701682

Cruising: Island Comeback

The U.S. Virgins Islands have surged back from the devastation of the 2017 hurricanes, with new infrastructure plans that will benefit charterers and cruisers alike. After hurricanes Irma and Maria roared through the Leeward Islands in September 2017, it was impossible to ...read more

albintoilet

Gear: Albin Pump Marine Toilet

Head Start Is there room for a new marine toilet? Albin Pump Marine thinks so, having just introduced its line of Swedish-built heads—ranging from compact to full-size models—to the American market. The toilets feature vitreous porcelain bowls and either wooden or thermoplastic ...read more

07n_45R2699

Multihull Sailor: Classic Cats

If you’re looking for a decent sub-40ft cruising cat, you have few choices when it comes to new-boat offerings. It is a well-known fact that the multihull market has taken off in a way very few could have predicted. Despite Hurricane Irma’s recent destruction of a large part of ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell. Got a tip? Send it to sailmail@sailmagazine.com Thanks a bunch  This scene is very calm and seamanlike. No frantic rope throwing or shouting. As he passes the line to the gent on the dock, the crew on the boat says, quietly and clearly, “Would you ...read more