Bob,
Before anyone can answer that question for you, I think you need to do an energy audit. The 4 GC batteries and 70A alternator (which I assume also has a multi-stage regulator) are a good start, but if you are planing to add a bunch of items that eat up the amps, you should find out what you have, how many amps they consume, and how you will replenish the amps. In very rough terms, 1A at 110VAC uses 10A at 12VDC. The PO was right. Inverters are real hard on batteries. With your alternator, I think you should assume each 40-50AH you use will take about an hour of engine time to replenish, and running a diesel engine for long periods with a very light load (just the alternator) is not good for it. Some of the items you mentioned can be really energy hogs. If you only use an energy hog for a few minutes (ie a microwave), it's no big deal. If you brew a couple of pots of coffee and watch TV for a few hours, you'll have dead/low batteries in a short time. Can you/should you do without them? Your boat, your choice. Another alternative might be to purchase a small portable generator, and forget the inverter. Many other owners love their Honda 1k and 2k generators.

How long do you suspect we'd need to run the engine per day to keep up with a Raymarine RL70RC ? It says 10W for b&w and 20W for color.

Darin,
For something like that measured in watts (10w or 20w), you really don't have much to worry about. 20 watts is about 1.7 amps (20watts/12volts=1.7amps). Run your RL70RC for 10 hours, and you've consumed 17 amp-hours (AH). Assuming the same alternator as Bob has, it would only take 15-20 minutes of engine time to bring the batteries back up. As a comparison, running a medium sized microwave thru an inverter for about 10 minutes would consume the same amount of juice from your batteries as the RL70RC does in 10 hours. (I hope my math is correct...I just did it in my head!)

Bob - I have the same setup of batteries and alternator. I added a 1000W invertor to run a 19" LCD display as well as occaisional microwave and coffee maker use. The coffee maker uses 10AH from the house bank, a worthy expenditure to keep the spouse happy. If you don't already have one, you might invest in a battery monitor, like a Link 10, to track your usage and remaining capacity. Microwaves need true sine wave power, so don't think you can get away with something low end.

Craig

Try this: [url]http://forums.catalina.sailboatowners.com/showthread.php?t=108970[/url]

Caprice has a 1000W inverter/charger, four golf cart batteries and a series 27 marine starting battery. We almost never anchor out for more than a day or two at a time without runnng the engine to get out of an anchorage. We have no problem that I know of making coffee every morning and cooking one meal each day with the microwave. The rest of the time we cook on the propane stove. We also burn two lights in the evening, watch TV and often run a 12 volt fan for a few hours. We are happy with this arrangement.

We do not heat water or run an A/C while on the hook. I suggest using a percolator on the propane stove if you anchor out more than a day or two without running the engine.

Bob:

There has been a lot of good info given here in the few post. One has to look at what one wants to achieve in the end and how much comfort. Along with that is going to come some pain. As in you need to know how everything works as adding a inverter does complicate things.

I have read and read trying to figure out what we needed. Making mistakes along the way as well. So careful planning is a must I feel in laying everything out.

I have in the last month added a prosine 2000 watt inverter, and a kiss wind generator. This adds to the solar we added a few years ago. As it is in prep for leaving to go south next year to the Bahama's. But as others have said on here you have to look at your power consumption. We have basically went over the entire boat and changed our whole power program. The link 10 or 20 is a must I feel if your going to go that far.

So we will see how it all works out this summer as it will be a good test for all the systems.