Think I need new House Batteries for my Mark II

[Noah]

Mick- Curious about the advantage of "pulling out the Honda after three days" instead of running the boat's engine to charge while on the hook?

[Mick Laver]

Hi Noah
Diesels really shouldn't be run for extended periods without a load. I'm sure there are others here that can give a more full explanation. The Honda is also a lot quieter and less likely to annoy the "neighbors."

[Noah]

Mick- curious; you said "...about three days before we drag out the Honda." What is your reasoning to use the Honda instead runninig the diesel?

[lazybone]

I'm sorta guesstimating..  A 90-100amp 12v alternator requires about 5-6 hp.
That's not free-wheeling for a small diesel.

[Clay Greene]

One alternative you might consider is that Trojan also makes a 12v golf cart battery that is a true deep-cycle battery.  We weren't really looking for the amp hour increase you would get from going with the four T-105s because we have regular access to shore power.  The two 12v batteries were less expensive than the four T-105s (equivalent in price to the 4Ds they replaced), fit easily in our battery compartment, and all of our existing wiring worked with the exception of one jump cable.   

By the way, we also installed a Balmar Smart Gauge, which I really like.  Simple and it seems to works well.

Anyway, food for thought.   

[Noah]

I'm sorta guesstimating..  A 90-100amp 12v alternator requires about 5-6 hp.
That's not free-wheeling for a small diesel.

Not sure what you mean here...?

[Mick Laver]

Noah
Sorry for the delayed reply, but I have a good excuse: a two-day transit from Catalina (Two Harbors-Oceanside, Oceanside-SD). Great weather, lousy wind. But what's that they say about a bad day sailing vs. a good day at work?

In answer to your question, quoting from the Book of Calder (Mech. and Elec. Manual): "All too many diesels in sailboats are run repeatedly for short periods of time, during which they do not warm up properly, or they are run for long hours at light loads (generally for battery charging and/or refrigeration at anchor). Both of these are liable to dramatically shorten life expectancy and increase maintenance." One of the reasons (quoting another source) is that " Light and no load operation promotes "souping", which is excessive oil escaping past piston rings into combustion chamber."

Others (including Mainesail) have pooh-poohed this viewpoint, citing the experience of long-term cruisers and people who run fleets of diesel equipment on land. There's a good discussion at https://svsmitty.wordpress.com/2013/09/25/running-a-diesel-at-idle/

This seems to be one of those "Your boat your choice" issues. For me, I have the Honda, it's quiet, and it sips fuel. I don't mind dragging it out every three days, but there are certainly times when just firing up the engine for an hour or so might be more convenient.