use of Generators and windlass'

Interesting on what is considered small. We have 20kW and 12kW on our 65. 80 amp and 45 amp. Basically we can run most things on the 45 except oven, water maker etc if you load watch. But yes 9kW would be too small to be useful for us.

We have a 1200Ahr invertor/house bank which we never run just to be quiet. The HVAC would drain it way too quickly. We use it during the day to keep the gensets off and supply the fridge, lighting and nav electronics.

Ironically, we run the gensets early morning when the wind drops and it heats up onboard. The gentle hum of the genset and HVAC is the best sound on the world for a beautiful sleep-in.

But it's worth noting the difference in boat style is a huge factor. Large slanted glass windscreens impart a phenomenal heat gain into the boat, which HVAC is absolutely required. Almost all of my windows are shaded almost all of the day, and HVAC just isn't required.

FWIW, in this debate between JWY and Capt J, I'm 100% with Capt J. It is down to personal choice, so I don't mean to argue aggressively with JWY; I'm just putting forward my view. I'm on my 2nd 80 footer (as owner and new build specifier) and on both I specified 2x identical 23Kva gensets. I run them mostly one at a time. I want the redundancy, and I want instant switchover if one sucks up weed or an impeller fails, etc. I would consider a 3rd small genset as Capt J says, but I generally don't want to give up the machinery space.

I totally get that it's bad for a genset to run at light loads, but exactly as Capt J says you manage that with say 5Kw of inverter. Then you fire up the genset to charge the batteries, and with 200amps of battery charging at 24v you are already loading the genset ~20-25% before any other loads you put on it. Then, in the final analysis, I might glaze the bores on my gensets. Exactly how much does anyone care about replacing a $25k genset at (say) 12000 hours instead of 20,000? It's peanuts compared with what you spend on a boat and the fun you lose if your 23kw genset drops an impeller during a party and you spoil the next 24hrs by limiting guests to 6Kw from some mickey mouse back up genset

The above also gives the batteries a tough life - deep discharges then recharges to only 90% - pretty cruel to a battery. So you just change them every 2nd year. Boating is about maximising fun, not babying batteries and genset bores, or listening to Northern Lights sales guys.

We use a similar but a little bit more advanced setup. Two equal type and sized variable speed generators of which one is normally capable of running the load by itself. But they are downsized to have them run in the 60 to 80 % load regime. If more power is required, the second genset starts automatically and synchronizes with the other set. The short time until the second genset delivers its load is backed up by the battery and inverter array. The two main gensets are setup in a switchable master/slave system to keep both gensets on equal operating hours. A smaller night generator is available for stby times. Works pretty fine and system handling is a real no brainer.

Example: On my sons 80 ft IPS boat there are two Fischer Panda 25i (25 KVA) 230 Volt single phase variable speed inverter/generators, set up as above plus one little 5000i night generator. All three gensets can work together. Four paralleled Mastervolt 3.5 KW Inverter/Charger deliver AC power from the batteries or convert 28 Volt DC power from the 4 x 220 Amps engine mounted alternators. They work together with the shore power or with the onboard power generation to cater for short power demands.

In my personell opinion, the times of old and heavy 1500 or 1800 RPM constant speed, RQV regulated generator engines with mechanical injection pumps on yachts and even bigger ones on commercial ships are a thing of the past. Modern variable speed gensets with electronically controlled common rail engines are (almost) always operating at optimum load and deliver higher ratings, run with less noise, use less fuel and run cleaner (under the bottom line not in specific fuel consumption of course). Sailing yacht A for example is equipped with these types of gensets. DC is the future on yachts and even on commercial ships.

If innovation is really unneccessary, why your guys are not driving your Ford T model anymore. It was a grat car .

Our boats until this point have had two identical generators or just one generator. So, another boat, another day, another decision. A 65' Sunseeker. Factory offering is a single Onan 21.5 kw. While Onan isn't our first choice, we're ok with it. Probably should be adequate for the boat.

So some pertinent information. We will install a watermaker. We cook on board a lot, either in the galley or with electric grills. We also use a washer and dryer a lot. Factory standards are 30 and 48 gph. We chose to install locally a 75 gph unit. We also have full A/C including for the crew cabin and we're adding A/C for the flybridge. We run our A/C or Heat nearly 100% of the time. We also are considering adding an additional freezer. We also have quite a few items hydraulically operated. We will be using the boat on the Loop and Inland Rivers primarily although some coastal to get from end of loop to a start of a new loop. So the choices are three:

1. Go with the single generator.
2. Go with a second Onan 21.5.
3. Go with a "half generator" Onan 11.5 kw.

A couple of notes on the generators size and weight.
A 21.5 is 44.4 in x 23.7 in x 27.5 in and weighs 930 lbs.
A 11.5 is 40.7 in x 22.3 in x 23.4 in and weighs 695 lbs.

In our situation there is no way option 3 is logical or fits. It's either a single generator or two identical generators. Those are the only two real choices for us to consider.

We also confirmed with Onan as we had done with NL, that with today's units the 50% load minimum is not an issue and that they are fine running as little as 25-30% load, although I don't see us running that. However, rather than run one unit at 80-90% we would run two at 40-45% if that choice arose.

Now, I'm only talking our specific situation on one boat with one set of equipment. I think anyone needs to evaluate their own situation.

If you want to investigate and invest, you can consider 2 generators which might run parallel and electronically controlled so the spare one to come up in case the need for more power is there.

Sorry, just realizd there is already more eleborate explanation on this...

Automation is great. When it works properly. I spend most of my days lately trying to figure out what went wrong on overly complicated automation systems.

The biggest problem, none of the automation systems are "marine grade". Sure they work flawlessly in commercial applications and they are all made from high quality components, but add in a few drops of salt water and things go south real quick.

I'm very "pro automation" I just wish the systems were a little more robust.