Generator size

What size diesel generator is needed to power a 32' trawler with reverse cycle heat / ac, electric stove, lights and other basics while anchored? Has anyone heard of Nexgen they make a 4K genset. I am working on figuring out how much the boat will cost above sale price before making an offer. Thanks Unclematt

You need to know what the sum of the loads are that you would be running all at the same time. We would need to know how you plan on using the boat and what creature comforts you desire. Suggest you get a copy of Calder's "Boat Owners Mechanical and Electrical Manual". I know a few people with Nexgens that seem happy. Look also at Phasor for "budget" gensets.

For a 32’ boat a 4KW genset seems fair. Keep in mind that you may need to do some load management. We have a 9KW on out 41’ and it is too big IMO. You do want to load the genset enough to get it up to temp. I would prefer a 6 or 7 KW in our boat but it came with the 9.

Unclematt said:

What size diesel generator is needed to power a 32' trawler with reverse cycle heat / ac, electric stove, lights and other basics while anchored? Has anyone heard of Nexgen they make a 4K genset. I am working on figuring out how much the boat will cost above sale price before making an offer. Thanks Unclematt

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I agree with what caltexflanc said.

I don't think a 4 Kw generator is big enough for an ac/reverse cycle heat and electric stove.

The AC start load is high and in combination with the stove or hot water heater running will pop the breaker unless you manage the loads.

My sense is that generator needs are based on the systems of the boat, not the boat's length.

Depending on how many AC units you plan to run, a boat with 2 units will likely be happier with a 6KW.

The other consideration is how much you plan to use it. The smaller generators are generally higher RPM units and noisier. If you plan to use it much, I would spend the extra money for an 1,800 RPM unit. Don't know if they are available below 8KW. This assumes that any you buy, will have a sound shield enclosure.

Ted

I had an older Chris with that size Genny, about the same size boat also. No air though.

If I had something going on the stove and the water heater kicked on, then the refrigerator the microwave would send it into overload. I just learned to turn off the water heater and don't use the toaster or microwave if I had the stove on.

Wasn't really a problem

pete

The Northern Lights is available in a 5 and 6kW in three cyl 1800rpm. Pretty heavy unit for a 32. I run a 5k NL in my 38, it powers 12k and 6k AC units, a water heater and a pancake air comp. Can run any three of those four. Can actually run all four but exhaust gets smoky. No electric stove.

Add up your loads, but to size the gennie reasonably expect to do a little load management. Like if cooking, turn the water heater off. No big deal.

The nexgen belt drive units are a little noisier and rougher than a slow turn 3-cyl, but not horrible. A little noise is way better than sweating in bed.

O C Diver said:

The other consideration is how much you plan to use it. The smaller generators are generally higher RPM units and noisier. If you plan to use it much, I would spend the extra money for an 1,800 RPM unit. Don't know if they are available below 8KW. This assumes that any you buy, will have a sound shield enclosure.

Ted

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I've had a 4.2 Kw Entec, a 4.5 Kw Westerbeke and a 5.5 Kw Westerbeke in Sandpiper.

The Entec was a 3600 RPM single cylinder generator but very quiet. It vibrated like crazy and the sympathetic vibrations were not pleasant. It was very small and light, 234# for generator and sound enclosure. I would not recommend it. Only reason I had it was because I was a dealer.

The two Westerbekes, 4.5 and 5.5 uses the same 3 cylinder Mitsubishi 1800 RPM engine. The generators are around 400# with enclosure. They are very smooth and quiet.

I have an Onan 8KW 1,800 RPM with the 3 cylinder kabota engine in sound shield, with lift muffler, exhaust silencer, and Soundown vibration isolation. Very quiet and no vibration.

Ted

I've always found my 6.5kw to be big enough. I wouldn't complain if it were a little bigger, but I wouldn't want much bigger. It's enough to run all 3 A/Cs (2x 10k and a 16k) and let the water heater cycle or use the microwave. It's also enough to run the big A/C or both small ones, all 3 stove burners and still have some headroom. It's not big enough to run everything on the boat at the same time like shore power can, but the generator doesn't need to do that.

There are some other threads out there regarding the cost of putting in a generator. Does the boat currently HAVE a generator? If not, the cost of the actual genny is probably not the major expense. Personally, on size, I would go with a 6+kw genny given what you've said you load is. You mention running Air Conditioners and other stuff at anchor, so I am assuming the boat already has the AC units and other stuff, but doesn't currently have a genny, sooooo . . . . figure at a minimum:

• find space for the generator in the engine compartment, or lazzerette, one that will allow maintenance to be performed.
• thru hull for raw water to the heat exchangers on the genny
• raw water pump
• raw water return
• fuel to genny
• fuel return to fuel tank
• exhaust plumbing/avenue to overboard
• wiring into existing battery systems/battery charger
• start battery for generator
• remote start/engine meter/load meter in cabin

The above is just a start. Figure a MINIMUM cost of 5k, just to install, IF you do all the labor yourself. If professionally installed, double it.
Figure minimum of 5k to purchase, so you are looking at from $10k (genny & materials to install) DIY, $15k minimum someone else does it.


Question: Might you consider another boat that already HAS a suitably sized genny already installed?

Slow goes it, Nailed it.

Friends with a Great Harbor 37 had a 5Kw genny. 4Kw should be plenty for a 32 ft boat with one AC unit and electric stove. Assuming only one 30A shore power cord.

Yep, if you can live happily on your boat with a single 30A/120V shore cord without tripping breakers, a 4kW should be fine. 120V at 30A is 3.6kW.

I have always thought of a generator as a replacement for shore power. 60 amp shore power 7,5-8.0 KW generator. 30 amp shore power 4.0 KW generator. 100 amp shore power 12 KW generator.

Most common shore power setups:

single 30A/120V 3.6kW
dual 30A/120V 7.2kW
single 50A/120V (pretty rare now) 6kW
single 50A/240V 12kW

The OP's 32 likely has one or two 30A/120V cords.

FWIW, my setup is 2x 50A/125V, so 12KW of shore power. The 6.5kw generator is nowhere near as much power and is correspondingly not enough to run everything. But it's also pretty rare to have a desire to run everything except maybe in extremely hot weather. I don't like running the generator overnight, so if it's so hot out that I need to keep the A/C running non-stop I'm probably going to be finding a marina where I can plug in anyway.

I had a Prairie 29 with a 4kw. It had a 16k AC and all of the other AC accoutrements. It ran everything fine. I will admit, it was a 4 cylinder Kubota if I remember correctly..Onan Generator. I always thought that was very strange. It was definitely labelled as a 4kw. But it could handle every single AC appliance all at once.
Current boat has an 11.5 (e)Onan....Smart generator. I love it. It has already saved my bacon. Shutdown in the middle of the night and it tells you exactly why it shut down...."Waterflow". Went into the engine room, cleared the strainer...back in business. Simple as that. I do believe it to be a bit oversized but I do have 2x16k ACs and 2x6k ACs along with a washer/dryer. Whenever I run it I try to load it up as much as possible but that usually amounts to the two big ACs and the water heater....probably a whopping 5kw.

You might check out Dometic Smart Start unit. My boat has two 16,000 btu heat pumps run by a single 5 kw NL generator. The Smart Start takes 65% out of load start spikes. No problems with generator overloads and my generatorj load is probable 75% or more making for a happy generator.

The only way to size a generator is to add up all of the loads and add 10%.

It is just simple math!

fgarriso said:

The only way to size a generator is to add up all of the loads and add 10%.

It is just simple math!

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Not necessarily good advice. If you add up everything and add 10%, you may end up with a really big machine that ends up spending most of its time running at 20-30% load 90% of the time and that is not good for the engines.

Best to size it modestly and tolerate some load management.

If you absolutely do not want to manage load, then size it as you suggest. Just understand there are downsides to doing that.

This applies especially to a smaller boat (like OP's 32). Not so much to a large boat, as that will usually have plenty of load and the physical size and weight of the machine is a non-issue.

FWIW, My 1986 41' Hatteras Came from the factory with a 50A, 240V shore power service which was just about right for two A/C's and all electric appliances. Unfortunately the engineers at Hatteras assumed that no one away from the dock would actually drop an anchor and cook! She came equipped with an 8kw (30A, 240V) genset. Then, to make matters worse, I installed a 240V watermaker. Life seemed to be a constant rerun of the "Green Acres" episode where Eva Gabor had to carefully add the numbers on her electrical cords in the kitchen to keep from blowing fuses.

When we finally declared our 8.5kw Onan close enough to death to be rid of it, we upgraded to a 12kw and life was good again! Last I heard, the Onan's three cylinder Kubota was still merrily providing power for an Amish woodshop.

For me, the moral of the story is that too much power isn't nearly as much trouble as too little.

Unclematt said:

What size diesel generator is needed to power a 32' trawler with reverse cycle heat / ac, electric stove, lights and other basics while anchored? Has anyone heard of Nexgen they make a 4K genset. I am working on figuring out how much the boat will cost above sale price before making an offer. Thanks Unclematt

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What shore power connections do you have? Is it a single 30 amp or dual 30 amp connections?

The 5.5 Kw generator is perfect in the winter running electric heaters and hot water tank.

In the summer at anchor, the 120 VAC holding plate freezer compressor and the battery charger are the only loads after the 15 amp hot water tank reaches temp. The compressor uses about 5 amps and charger consumption declines as the battery gets charged but starts at around 20 amps when the batteries are down 50%.

So in order to keep the generator loaded after the water heater turns off, I have to run an electric heate outside the boat. When I had the 4.5 Kw generator, did not need to run a heater but sometimes had to manage loads.

Reason to correctly size the generator.

I have an’06 IG 32 with a 5kw split genny. I have to manage the loads to keep from tripping. I wish I had a 6-7 kw. Below is a load test I did with most of my heavy draw stuff:

Sea Neff 110V Amp Loads

House Bank
• Water Heater - 12 Amps
• Microwave Oven - 10.5 Amps
• Kuerig Coffee - 11.7 Amps
• Hair Dryer - 13 Amps

A/C Bank
• A/C Water Pump - 2 Amps
• Both Air Handlers - 3 Amps
• Forward A/C Compressor - 5 Amps
• Salon A/C Compressor - 7 Amps
• Peak Amperage with both A/C's - 31 Amps

Hope this helps.

hi,

we anchor out 95% of the time on our ms 34 pilot. it is all electric with a 12k ac. we have a 3.5kw nextgen and have never had a problem as long as you managed your loads. mornings we do battery charge + coffee. when coffee is over i run water heater + charger. afternoons will run ac + charger. we grill a lot but if we use the stove top there is no ac or wh.

Unclematt said:

What size diesel generator is needed to power a 32' trawler with reverse cycle heat / ac, electric stove, lights and other basics while anchored? Has anyone heard of Nexgen they make a 4K genset. I am working on figuring out how much the boat will cost above sale price before making an offer. Thanks Unclematt

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I have a 36’ trawler. Two AC units, microwave, electric oven, small fridge, water heater, various outlets with “stuff” constantly plugged in. I have a 9.5kw

Adding a generator or even changing one can wind up becoming a large and very expensive project. If you are buying a boat that will need that, I suggest you have a professional look at this boat and give you an estimate. Even if you have to pay for this info, I think you will be glad you did and surprised at the cost.

My Grand Banks 32 has its original Westerbeke 4.5 kW genset and it seems like the right size for the boat. She has reverse-cycle A/C, microwave and a gas stove. The Westerbeke is suffering from a worn-out water jacket that is no longer available and I'm dreading replacing this otherwise perfect genset.

I only use the generator when I'm running the A/C at anchor or have some other specific need for it, like running power tools or recharging the house battery bank. The prior 3 owners must have done the same, because it has very low hours even though this was a Florida boat for most of its life.

Northern Lights 8 kw is what I had in my GB32 with an electric galley.

The make doesn’t matter, cost and maintenance availability are more important. The most important is to determine the expected loading and get on sized such that it has to work a bit. Too large and it won’t have enough load and it will fail prematurely. Whatever vendor you decide on should be able to advise.