Electricity while running?

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
L

lowcountry

Veteran Member
Joined
Nov 1, 2016
Messages
40
Location
United States
Vessel Name
Endeavour
Vessel Make
'87 Island Gypsy
I know this is a total newb question and I've been hesitant to ask, but here goes...

We're planning on purchasing a 35' - 40' aft cabin style diesel for a summer cruise up and down the intracoastal. We're planning on mostly traveling and anchoring during the week and staying in marinas(shore power) during the weekend.

While our engine is running, will it also be able to run the boat's electric system? ie, our refrigerator, a/c, and outlets?

Or, does the diesel generator also need to be running while underway? Can the generator run while underway? Is it ok for the generator to run 24/5?

Thanks!
 
Generally, your generator would supply house power while away from the dock, but you can wire in an inverter to run a few things off the battery while underway. We had a small household fridge that could be switched over to the inverter while we were out. Your house lights will also likely be wired into your battery, so those should work while out. Things like A/C, water heaters, etc will likely need the generator.
 
Engine supplies 12V to systems such as many refrigerators, lights, charges batteries...


The Generator is usually required for Air Conditioning or heating and things plugged into wall outlets, and battery chargers that feed batteries not hooked into a system where the engine alternators charge and power things.
 
lowcountry said:
While our engine is running, will it also be able to run the boat's electric system? ie, our refrigerator, a/c, and outlets?

DC system yes, AC system (120/240 VAC) not normally unless you have an inverter or if the refer is dual voltage 12VDC/120VAC. If you really need air cond when your moving, then you will need the genny.

Or, does the diesel generator also need to be running while underway?

Usually dont need the genny underway unless running air cond.

Can the generator run while underway?

Yes

 Is it ok for the generator to run 24/5?

Yes as long as its properly loaded and maintained. Gets expensive though when you figure in fuel, maintenance, and eventual replacement costs.

Thanks!
Click to expand...
 
Thank you for the quick answers. This is what I figured/hoped.

Basically, at anchor, we'll just need to run the generator if we want a/c and outlets.

Thanks!
 
Last edited:
lowcountry said:
Thank you for the quick answers. This is what I figured/hoped.

Basically, at anchor, we'll just need to run the generator if we want a/c and outlets.

Thanks!
Click to expand...

Not necessarily. It depends on how you boat is equipped. Many have AC oven/stoves.

And many have little or no real house battery capacity that would allow you to anchor out for anything more than a night without running the gen or engine to recharge the house battery bank.
 
I have Magnum MS-PAE inverters. They supply 120/240 with a single inverter. All ac power can go thru them and when switching off shore power or generator, inverter takes over the load. When shore/generator power returns, inverter charges batteries. I run an alternator on one main that keeps up with inveters so no generator needed when running mains. I easily run double door reefer, chest freezer, lights, computers, etc. on inverter power. Up to 4 inverters can be linked for 16kw. I have 2 for 8kw.
All my lights, except nav, are 120v ac. I don't like the dc light choices.
 
Well before you purchase a vessel suggest you educate yourself on this subject by doing some reading and boat touring. For reading buy Nigel Calder's boat electrical system book and Google Steve D'Antonio for numerous articles.

For boat touring look at later model Ocean Alexanders, Nordhavns or DeFevers which should all have these three things you'll want:

Genset
House Bank
Inverter

Each of the above three have their own debate points regarding brand, size and age. Keep in mind a good RV will have the same three ingredients so the technology and equipment is well proven with a large audience.

Good luck and take your time.
 
I also have an inverter. Ran everything except A/C from the batteries. Even ran the microwave. Granted this was just playing around with her for a while. I like the idea that my fridge goes d/c automatically. I have almost completed changing out all lighting to LED to reduce the battery use.
 
lowcountry said:
Basically, at anchor, we'll just need to run the generator if we want a/c and outlets.
Click to expand...

Hot water is another that often requires genset time, although there are alternatives to solving that.

For a summer cruise in ICW territory, you may well (quickly) find you prefer running the AC (or ACs) while underway. Especially if you and/or some of your crew (and/or pets) may be "indoors" during much of the trip. Cabins can get pretty darned toasty, otherwise, and it can make a decent difference when you arrive at a marina and already have interior living space all cooled down.

Since you're still shopping, check out threads on cooking (propane vs, electric, etc.) to inform yourself about pros and cons of each. If you decide on electric cooking, or if your boat choice ends up coming with that even if you're ambivalent, you'll likely have to run the genset during meal prep times. (FWIW, that's not a disadvantage for us, since we also use that time to charge the batteries and heat water.)


Check for threads on fridge alternatives too. Some run AC/DC units, some have AC only and need an inverter, etc. and you'll want to be sure you understand the pros/cons of each.

-Chris
 
We have twin alternators and with an inverter we can easily run all onboard sytems while underway, including the microwave. We do however have a propane range and no air conditioning. As stated in earlier posts, AC and likely an electric range would require that the genny be running to use these. You will really need to understand the boats systems and capabilities before purchase.
 
A very common question. I addressed it in one of the blog posts from our last trip. It gives a very basic overview of our typical electrical usage while travelling. As they say, YMMV. But I think our experience is pretty typical.
 
These are all great responses. Very exciting about learning all this!
 
Donna said:
I like the idea that my fridge goes d/c automatically. .
Click to expand...
Ditto on the ac/dc refrigerator....now, if my ice maker was also ac/dc, I wouldn't have to use the genny at all! (While running, that is.) :blush:
 
One other note on the water heater. Most boats are plumbed to heat the water while underway from the main engine. So if you take your shower soon after your days travel, no need to start the generator for hot water.
 
FOG said:
Most boats are plumbed to heat the water while underway from the main engine. So if you take your shower soon after your days travel, no need to start the generator for hot water.
Click to expand...
Good point! In my case, I have warm water about 24 hours after shut down.:blush:
 
lowcountry, in your learning, you will see "AC" used as a short form for both air conditioning, and alternating current. It can get pretty muddy when both are being discussed at the same time.

RB
 
FOG said:
One other note on the water heater. Most boats are plumbed to heat the water while underway from the main engine. So if you take your shower soon after your days travel, no need to start the generator for hot water.
Click to expand...

My water stays hot for hours after the engine is shut down.

Many marine refrigerators run on 120 volts AC when it's available and switch to battery power automatically. This is what you want.

If your boat has a propane stove, your electrical needs can be met with an inverter and a bank of four batteries (plus the engine starting battery). This does not include air conditioning though.
 
With few exceptions, my boat is factory wired for AC electricity and I only have a few things that are on the DC load.

We star the generator before we start the main engines and the genny runs until we are plugged into the marina. At around 1GPH diesel consumption per hour it will such down some fuel but going to bed when the room is 65 degrees is well worth it!
 
lowcountry said:
I know this is a total newb question and I've been hesitant to ask, but here goes...

We're planning on purchasing a 35' - 40' aft cabin style diesel for a summer cruise up and down the intracoastal. We're planning on mostly traveling and anchoring during the week and staying in marinas(shore power) during the weekend.

While our engine is running, will it also be able to run the boat's electric system? ie, our refrigerator, a/c, and outlets?

Or, does the diesel generator also need to be running while underway? Can the generator run while underway? Is it ok for the generator to run 24/5?

Thanks!
Click to expand...
Yes the generator can be ran 24/7. As the others said, it depends on how your boat is set up. All my appliances are 120 so the generator goes on before the mains come on and runs until I reconnect to shore power how ever long that may be. I have ran 6-71 Detroit Generators for 6 weeks straight without taking them off line on tug boats. They like to run. The current ship I am on we have been running the generators for 6 months straight and won't be shut down until our yard period in December. For those who may be wondering we change the oil every 2800 hours. Yes 2800, I do not understand why some here say every 100 hours or each season for oil changes.
 
The starting point for any of this is cruising grounds and type of cruising. 90% of the time we're going to be running air conditioning or heat, so if not hooked up to the dock, we'll be running a generator regardless. We cruise mostly in areas that would be uncomfortable without air and occasionally in areas where heat is needed. We live in Fort Lauderdale. Now for those in the PNW the equation is considerably different.
 
FOG said:
Most boats are plumbed to heat the water while underway from the main engine.
Click to expand...


I think maybe more correct to say "many" boats... given that there are pros and cons to that...

-Chris
 
knotheadcharters said:
For those who may be wondering we change the oil every 2800 hours. Yes 2800, I do not understand why some here say every 100 hours or each season for oil changes.
Click to expand...

Maybe they are afraid that the oil will accumulate moisture?

I run the heck out of my genny and never think twice.
 
Generators have their place. Solar equipped boats have substantially reduced generator usage/needs. You may want to add this to your study collection.
 
knotheadcharters said:
For those who may be wondering we change the oil every 2800 hours. Yes 2800, I do not understand why some here say every 100 hours or each season for oil changes.
Click to expand...

That generator is nothing like the Onan, Kohler, Northern Lights, etc. found on cruising trawlers. Northern Lights recommends changing the oil every 200 hours. If you waited 2,800 hrs to change the oil on one of those, it would look like sludge due to oxidation, soot accumulation and loss of additives.

But I do agree about not changing oil each season if you run less than 200 hours in a seasn. That might have been valid in the days of high sulfur diesel which can leave acids sitting in the oil over the winter. But not with today's low and ultra low sulfur diesel.

David
 
If our boat is unplugged from the dock, one of our generators is always running. I shut the generator and all systems down when we go to shore while anchored though.

We have two generators, so my morning ritual is to check fluids and status of the generator that isn't running and then fire it up and switch generators. This helps me catch any mechanical issues before they are a real problem. We put approximately 600 hours on each generator (1200 hours total) over each summer while cruising the Bahamas. Oil changes every 200 hours.

Our prime directive is comfort and things should be the same if we are plugged in to the grid or disconnected from it.
 
knotheadcharters said:
.............. For those who may be wondering we change the oil every 2800 hours. Yes 2800, I do not understand why some here say every 100 hours or each season for oil changes.
Click to expand...

Well, considering how much it would cost to replace a diesel engine, many of us choose to follow the manufacturer's instructions.

If you know more about the engine's needs than the folks who designed it, then it may make sense to set your own maintenance schedule.
 
With a largecbattery band and modest power management I only run the genny 2 hours a day. 1 in the am and 1 in the pm.
 
Last edited by a moderator:
You must log in or register to reply here.

Similar threads

J
Running on board generator
2
Replies
31
Views
2K
psneeld
psneeld
M
House electrical
Replies
21
Views
2K
dutch-barge
D
M
Owning a 40 foot trawler with no generator?
Replies
25
Views
2K
Cold Duck
Cold Duck
C
Generator runs fine but no AC current flow?
Replies
10
Views
900
Steve1.0
Steve1.0
M
gen set not running a/c but everyhting else
Replies
15
Views
812
C lectric
C lectric

Latest posts

Back
Top Bottom