You have a Morgan 41? What size is your engine and how big is your alternator? I imagine that your engine is somewhere around 50 horse? A 120 amp alternator is barely going to put a load on the engine. Over time, you run the risk of the exhaust elbow “coking up” with un burnt hydrocarbons because there isn’t sufficient pressure to blow them out. They build up over time, restricting the exhaust flow, resulting in higher pressures and temperatures. Ultimately causing elbow cracking or burn-through. Diesels are happiest running WOT. Is your alternator an externally regulated one?
Engines, especially older engines, do not like to idle. The engine does not get hot enough to burn off impurities in the oil. The fuel injection is not designed to be very accurate at idle, so the fuel burn is not complete and the exhaust will be sooty. This leads to build up in the exhaust system.
In short, diesels like to be run at cruising RPM and not idle speed. IMHO, if you need to run the engine to charge batts, put the boat in gear. That will put more load on the engine.
I guess I didn't mention that we are live-aboard cruisers. 10 watts is akin to spitting in the ocean. We've got computer, microwave, coffeemaker, TV, etc. all the comforts of home.
Priscilla, > >
I like your answer best (for my purposes, at least, it keeps me out of trouble with Suzi)
Westerbeke 55B (about 4 years old 853 hours) with 170amp alternator, set to 100 amp output max with Link 2000r. We run at about 1400 rpm when charging batts - it runs about the same temp (~180) when we are moving the boat as when just charging batteries.
Got it used - 2000 watt for only $500. I am the Frugal Mariner, you know!
So am I O.K. here? Can I run the diesel or should I go with Mr. Noisy?
Barry, me too were educated on this, including specialists observating same advice. Steve, I had red this article before, wich corroborate to people like Nigel Calder. What I couldn't explain is in a heavy traffic city like here, people spend (an average) 3 hours per day in traffic, mostly iddling the engines, but diesel cars/van/truck are still very reputable for longevity and reliability. I can understand the efficiency math (running a big beast to power tinny 500W to your DC system), where oversized generators are wasting more fuel per Watt, if compared to smaller unities) but cannot understand why marine diesels wear faster if iddling, copared to automtive diesels iddling. Should marine learn a thing or two from automotive industry ?