Howdy group,
All the yachtsmen I know who run a diesel use only 'diesel fuel', which
is light and expensive. However, in the merchant navy we use bunker
fuel whenever we're going to be running the engine for a long time,
without varying RPM.

It's thicker than molasses at room temperature, but when suitably
heated, it runs enough to be used in a diesel engine. It also costs a
fraction of regular 'diesel fuel' (aka "Champagne"). The engine is
started with light diesel fuel until it's running hot enough, then the
fuel mixture is gradually changed over to bunker. If the ship comes to
manoeuvering conditions, then the mixture is switched back to light
fuel. They always go back to light fuel before shutting off the engine,
too, to 'clean' the insides for the next start-up.

Now I'm wondering why we don't do this in cruising yachts, where the
engine is running constantly for days, especially considering the fuel
prices of late. All one would need is a heated holding tank and a way
of adjusting the fuel mixture. Then again, I'm not a marine engineer.
Am I missing something?

Regards,
-Max