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Old 02-25-2015, 08:28 PM   #1
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ac power at sea

When underway on a 2 engine trawler shouldn't there be some ac power available?
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Old 02-25-2015, 08:31 PM   #2
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If you want it but not absolutely necessary...
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Old 02-25-2015, 08:31 PM   #3
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If you have an inverter or a generator, then yes.
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Old 02-25-2015, 08:32 PM   #4
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We run our generator practically every where we go, but it's not a necessity.
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Old 02-25-2015, 08:40 PM   #5
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The capacity of the engine's alternator might be sufficient to operate air conditioning while the engine is operating. Certainly, with an inverter, the alternator's output can be the source of alternate current.


Do have an inverter but not a genset, but then, I don't have air conditioning nor an electric galley. Use AC for AC outlets (power a drill, charge a cell phone, etc.), air compressor, and rarely, water heater (also heated from engine).
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Old 02-25-2015, 08:41 PM   #6
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My Inverter /charger ( 3000 W/24 V/70 Amp) supplies all the power I need and I only have a 25 amp charger on the Gardner.
I also have a 5 KVA cruise alternator that supplies 240 V/ AC when at cruise RPM .
1250 RPM/50 Hz
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Old 02-25-2015, 08:57 PM   #7
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My Inverter /charger ( 3000 W/24 V/70 Amp) supplies all the power I need and I only have a 25 amp charger on the Gardner. ...
Pathetic.


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Old 02-25-2015, 09:13 PM   #8
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Always tried not to use the genny at sea.Part of the frugality of saving resources "Just in case" However i've used solar well on my last 2 boats. I have 2x120hp lehmans on my Cheoy Lee. I only use the alternators for the engine batteries, saving loss of HP from the engines. I lose about 5hp driving my stabilzer pump of the port engine. I removed my bimini when I bought the boat, and built a hard bimini, followed by 4x 235watt solar panels. These supply up 80 amps at the right time of the day and run as per the demand. It enables me to run all 110volt fridges, galley etc. and all 12volt services throughout the boat all day. They have already paid for themselves. We only run the genny at night for the A/con or a major oven etc in the galley. We tend to use the 110volt inverter etc for the daytime cooking etc.All in all the fuel savings are significant particulary here in the Caribbean,where fuels $5 a US gall.
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Old 02-26-2015, 12:46 AM   #9
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have a 14 kw Onan that we run when on the hook that gives us 50 amps but seems we should also have some ac power when we are underway from the twin perkins. What am I missing?
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Old 02-26-2015, 01:05 AM   #10
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unless you have a 110v ac alternator on one of the engines or an inverter and battery system you have to run the onan if you want ac power
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Old 02-26-2015, 06:20 AM   #11
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have a 14 kw Onan that we run when on the hook that gives us 50 amps but seems we should also have some ac power when we are underway from the twin perkins. What am I missing?
Most newer boats have an inverter or an inverter/charger that converts 12v DC to 110v AC. If you have an inverter, it either isn't working or AC isn't turned on at the panels or there is a wiring problem.

110v AC alternators on engines in boats are rare but you could check your engines to see what the alternator ratings are if you have more than one alternator. Most likely they are 12v.

You do have the option of running your Onan while underway and some boats run their gennys all the time.
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Old 02-26-2015, 07:15 AM   #12
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If the boat will be operating big hours under way, 2 solutions come to mind.

A pair of large bus alternators m 24V 300A or even the 12V 250A units would power large enough inverters (4KW) for air cond , washing machine dish washer and the rest.
A lightning side strike could wipe them all out.

For a new build I would suggest simply going to a hydraulic system.

This would power, steering ,bow /stern thruster, stability fins, windlass , boat hoist , fire pump/deck wash and large bilge pump. Hyd engine start is possible.

A 6KW hyd driven gen head would provide modest AC power underway , the noisemaler//get home would be hyd , so power is not lost when not underway

Most of these can be repaired worldwide with few parts , seals, specific to one mfg .
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Old 02-26-2015, 08:42 AM   #13
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My experience is, if you have a jenny, it needs to be on most of the time while at sea. Under a medium to heavy load. If I don't do this, the generator cannot be expected to operate well when I really need it.
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Old 02-26-2015, 09:02 AM   #14
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Originally Posted by henryj2 View Post
When underway on a 2 engine trawler shouldn't there be some ac power available?
No, not unless you have an inverter and it's on or a cruise generator or a regular generator, etc. The number of engines (2) has nothing to do with providing AC power. (Maybe I don't understand the problem...)
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Old 02-26-2015, 09:19 AM   #15
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Even in FL we did not find it necessary to run A/C there fore no genny for our usual day trips. Running the genny to cool the cabin might have been necessary if we had more than two of us on a trip and in hot weather a cool cabin is nice when you get to port and finish tying up.


Was always nice to air out the boat while under way.
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Old 02-26-2015, 10:45 AM   #16
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I have a 8KW Onan Genny, so AC power isn't a problem here. But I do remember seeing an engine mounted AC generator that also had a clutch. You could turn it on with a switch and like magic you had AC power for the boat while running the engines. It was on a boat we looked at when we were shopping for a boat.
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Old 02-26-2015, 11:03 AM   #17
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My experience is, if you have a jenny, it needs to be on most of the time while at sea.
Not necessarily. Our genset has about 1/4 the hours of the mains.

A well thought our electrical system utilizing an inverter and storage batteries is quite common to keep genset use to a minimum. On engine alternators at 12/24 volt can normally get the house banks charged up during a day's cruise.

Increased time at anchor vs cruising, water makers, Subzero freezers, lots of guests taking daily showers, TVs nonstop, electric heat or AC and washer/dryer can require genset run time to increase. But, a well tended genset is pretty cheap to run and can be very quiet.
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Old 02-26-2015, 11:10 AM   #18
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Not necessarily. Our genset has about 1/4 the hours of the mains.

A well thought our electrical system utilizing an inverter and storage batteries is quite common to keep genset use to a minimum. On engine alternators at 12/24 volt can normally get the house banks charged up during a day's cruise.

Increased time at anchor vs cruising, water makers, Subzero freezers, lots of guests taking daily showers, TVs nonstop, electric heat or AC and washer/dryer can require genset run time to increase. But, a well tended genset is pretty cheap to run and can be very quiet.
I agree...about 1/4 the mains time is good for the genset....

Many probably have less than 1 hr per month though on a genset and lightly loaded at that.....

I have a friend with a sailboat that runs his main about 8 hrs a month...I tell him he shuld turn on the genset and run it just as much...he looks at me like that genset is going to be left to his greatgrandkids and shouldn't be run at all. I tell him it may not last his lifetime if he doesn't run it.

Everyone has to evaluate their boating style and task the genset accordingly for max life.
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Old 02-26-2015, 11:11 AM   #19
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As Sunchaser put it, at sea cruising we don't need the generator except to run the stove.

We have a 3KW inverter/charger and a reasonable house battery bank. A day of cruising charges the batteries using a 150 amp alternator.

The generator comes into play when we are at anchor as a way to replenish the batteries.
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Old 02-26-2015, 12:06 PM   #20
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This is really a personal taste type question, I've seen some people fire up the gen right before leaving so "everything" stays on. For some boats with limited ventilation (think sport-fisherman) its almost a necessity.

I personally do not run with it on, mostly since I don't need it and 2 I cannot hear it running which is not something I like.
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