Gas vs Diesel generators.. Help? (Little Hondas vs Fisher Panda Style)

[smj]

Originally Posted by Dockhead

Avoid petrol generators for all the reasons noted: short lifespan, noisy at full throttle, extremely dangerous fumes (people die every year), fuel storage problems, less efficient.


Avoid Fisher-Panda. Not to put too fine a point on it -- they are carp. Dig through the archives of this site to find more horror stories than you can read in a weekend.



NexGen is the best cheap marine diesel generator (a company called "Phazer" make a similar one); a very attractive unit because of its simplicity. Otherwise, Onan, Northern Lights, Kohler, which are all continuous-duty rated and will last a lifetime.


Size the generator carefully if you are going to do propulsion with it. 6kW is less than 10hp at the prop. If you've got enough battery capacity, you don't need to size for short term peak power demands, but if you expect to motor all day in the ICW, you will need to size it for average consumption in that duty cycle. I bet it's more than 10hp.



Good luck and let us know how you get on.

Captain Shacks needs are probably better served by a large diesel generator, but for a lot of people a built in diesel generator would be way overkill and a waste of money, space and additional weight.

[Grith]

Originally Posted by CaptainShack

Thats a cool looking boat. Neat solution to get around the honda noise when around neighbors. Hows the power draw induction cook top? We've been using an old Alchohol stove and have been fairly impressed with it. Bit sad new ones are so hard to find.

Also whats that hot water service? Sounds interesting.

The portable induction cooktop currently sits on a board mounted over our alcohol stove. Good old redundancy backup for remote cruising issues.
Over a days cooking and cups of tea and coffee it averages about 1000watt hours of consumption.
Our electric storage hot water is a conventional insulated stainless steel yacht 25litre unit with plumbing available for engine heating as well but as we have a big outboard that is unconnected.
It uses a 800w 240v immersion heater and takes about 30 minutes and 400watt hours to fully heat up.
Being an inshore trailable cruising yacht we tend not to cook under sail or in significant waves.
It does look as though we will be able to leave the Honda generator behind on extended spring/summer/autumn cruises but always have the Honda available to carry if doing mid winter again like our last 6 weeks cruise.
We have added more solar panels now since this shot taken last August.

[Adelie]

Originally Posted by rslifkin

The small air cooled gas generator will be dramatically less efficient than an installed diesel unit. I did an analysis on this a while ago, which can be found here: https://www.cruisersforum.com/forums...ml#post3079298

For engines the same size diesel uses less fuel than gas/petrol.

Where the gas engine is sized to the demand and the diesel is significantly oversized then the gas can just as fuel efficient or more efficient than diesel.

See my post: https://www.cruisersforum.com/forums...ml#post3736641

First the OP needs to determine their electrical needs. It sounds like they want electrical power for propulsion.
If that is the case, how fast to do expect to go in flat water, no wind conditions.

They have a Prout 33, 30' LWL and 9500lb lightship weight.
Based on data collected from various electric propulsion vessel I would expect you to need 1700W or so to make 4kt and 3500W or so to make 5kt.

As a catamaran the vessel will probably be weight sensitive so the prime mover (to use a train term) needs to be sized to the vessel.

The Honda EU3000iS is $2800, weighs 131lb, is rated for 2800W and provides 5.68kWhr/gal at full load.

A Honda EU2200i is $1400, 47.4lb, 1800W, 5.76kWhr/gal

Fischer Panda AC 7 Mini - $?, 350lb, 6500W, 8.67kWhr/gal.

For an FP-8000 I found that it consumed 2.2kg/hr producing 6kW from 2008 Victron paper.
https://www.victronenergy.com/upload...7-jan-2008.pdf
2.2kg = 4.84lb / 7lb/ gal = 0.69gal/hr. Add 8% for the 6500W output thats 0.75gal/hr.
6500W / 0.75gal/hr = 8.67kWhr/gal.
If demand drops to around 3kW efficiency drops to about 6.9kWhr/gal
At about 2kW efficiency is 4.33kWhr/gal
At about 1kW efficiency is about 2.9kWhr/gal.

Let's assume that the OP will not run at full throttle full time, let's say they aim for 4.5kt boat speed so they need about 3000W for that.

Any of these motors will do. For the HondaEu2200i the OP would need to get a Companion motor for $1500. The 2 motors hooked together will produce 3600W and weigh about 95lb. Together these weigh 3/4 what the EU3000 weighs and get slightly better fuel economy.

The FP7 weighs 3.6x what the pair of Honda weigh, but have a 20% fuel efficiency advantage at 3500W demand. It will also be quieter. In order to supply the cooling water to the FP there will be some extra weight and significant extra complexity.

As electrical demand drops efficiency for both the FP and the twin EU2200s drops until about 1800W then, one of the Honda shuts off and the efficiency goes back up to 5.76kWhr/gal and remains significantly better than the FP.

If you want to push the boat at 5kt, the EU3000 probably is a little shy.
The twin EU2200s could probably do it and perhaps a bit more.
The FP should have no problem getting the boat to 6kt or so.

All of this is predicated on finding a charger that can convert the AC output from the generators to DC. There aren't many chargers that can take all that power and turn it into the voltage you want. Above 1200W-48v chargers start to get stupid expensive. You could buy multiple chargers, which would be good from a redundancy stand point. From a redundancy and cheap to replace standpoint the Twin EU2200s would also have an advantage.

[abroadreachtrvl]

Think about a single 6/8/9.9 outboard (share with dinghy) on a bracket as a range extender when needed.

The honda 2200 has a 3.1 hp engine, between the stacked inefficiencies of generator, charger, controllers,motor,ect you will probably will get 1-2hp of that at the propeller.

Probably more economical from both cost and fuel consumption standpoint.

[Dockhead]

Originally Posted by smj

Captain Shacks needs are probably better served by a large diesel generator, but for a lot of people a built in diesel generator would be way overkill and a waste of money, space and additional weight.

Well, it depends on how you use your boat.


I'm very pleased with my diesel generator, which was part of the original build of the boat (a Kohler 6.5kW heavy duty unit). It's almost inaudible so so you just run it as much as you need it and don't think about it, and there's always abundant power on board. The function is somewhat duplicated by the school bus second alternator on the main engine, but the genset is worth its weight in gold in different circumstances, like, for example, long distance ocean race when you're not allowed to start the main engine. And anyway, redundancy in something critical like that is a really good thing.

[smj]

Originally Posted by Dockhead

Well, it depends on how you use your boat.


I'm very pleased with my diesel generator, which was part of the original build of the boat (a Kohler 6.5kW heavy duty unit). It's almost inaudible so so you just run it as much as you need it and don't think about it, and there's always abundant power on board. The function is somewhat duplicated by the school bus second alternator on the main engine, but the genset is worth its weight in gold in different circumstances, like, for example, long distance ocean race when you're not allowed to start the main engine. And anyway, redundancy in something critical like that is a really good thing.

As I said, it depends on your needs. We have a very simple boat, by choice. No need for ac’s, washer and dryers, dish washers etc. The small Honda generator is used maybe once every 3 months for battery charging when the solar panels don’t keep up. It wouldn’t make sense for us to ad the extra cost, weight and lack of space on our performance catamaran.

[Dockhead]

Originally Posted by smj

As I said, it depends on your needs. We have a very simple boat, by choice. No need for ac’s, washer and dryers, dish washers etc. The small Honda generator is used maybe once every 3 months for battery charging when the solar panels don’t keep up. It wouldn’t make sense for us to ad the extra cost, weight and lack of space on our performance catamaran.

Sure. A performance cat is a different kettle of fish altogether. And of course any cat, performance or otherwise, has vastly better places to mount solar panels, than any mono which hopes to sail decently, so there's that.



But the OP has a cruising cat which has had the diesel engine removed. It will perform better if he doesn't add the weight back in, but he has that option if he wants it.


Ironically what I would probably do in his place is replace the diesel propulsion engine. Put a heavy duty second alternator on it for generating electrical power. This would be simpler and more efficient. But -- to each his own.


Someone above suggested an outboard for occasional propulsion, which could even be shared with the dinghy -- I think that's also a very good idea. That would take care of propulsion, and solar could take care of domestic needs on a small cat. A setup like this would be cheap, simple, reliable.

[smj]

Originally Posted by Dockhead

Sure. A performance cat is a different kettle of fish altogether. And of course any cat, performance or otherwise, has vastly better places to mount solar panels, than any mono which hopes to sail decently, so there's that.



But the OP has a cruising cat which has had the diesel engine removed. It will perform better if he doesn't add the weight back in, but he has that option if he wants it.


Ironically what I would probably do in his place is replace the diesel propulsion engine. Put a heavy duty second alternator on it for generating electrical power. This would be simpler and more efficient. But -- to each his own.


Someone above suggested an outboard for occasional propulsion, which could even be shared with the dinghy -- I think that's also a very good idea. That would take care of propulsion, and solar could take care of domestic needs on a small cat. A setup like this would be cheap, simple, reliable.

Someone recommended twin 9.9hp Yamahas and I recommended a single 25hp Yamaha outboard, both those options would be cheaper, simpler and probably more reliable. I’m not sure what type electric motors he’s planning on using but the outboards are kept clear of the water when not in use causing less drag and less maintenance.
For the cost and weight savings one could ad a huge solar array and lithium setup.......if needed!

[Dockhead]

Originally Posted by smj

Someone recommended twin 9.9hp Yamahas and I recommended a single 25hp Yamaha outboard, both those options would be cheaper, simpler and probably more reliable. I’m not sure what type electric motors he’s planning on using but the outboards are kept clear of the water when not in use causing less drag and less maintenance.
For the cost and weight savings one could ad a huge solar array and lithium setup.......if needed!

Agreed! That would be a great setup, and with plenty of emergency propulsion power when needed.



Outboards bring the ugly problem of petrol on board, but there are SO many other advantages for a small cruising cat that doesn't need mechanical propulsion all the time. So great to have the prop out of the water when not needed, just to name one of those advantages.

[rslifkin]

Originally Posted by Adelie

For engines the same size diesel uses less fuel than gas/petrol.

Where the gas engine is sized to the demand and the diesel is significantly oversized then the gas can just as fuel efficient or more efficient than diesel.

See my post: https://www.cruisersforum.com/forums...ml#post3736641

First the OP needs to determine their electrical needs. It sounds like they want electrical power for propulsion.
If that is the case, how fast to do expect to go in flat water, no wind conditions.

They have a Prout 33, 30' LWL and 9500lb lightship weight.
Based on data collected from various electric propulsion vessel I would expect you to need 1700W or so to make 4kt and 3500W or so to make 5kt.

In a hybrid propulsion setup, I'd expect that once you fire up the generator, you'll be running it at max continuous load regardless of size. Whatever extra power isn't being used to push the boat would be used to recharge the batteries.

[PIPER28]

I have Petter diesel generator/from my 39 Gulfstar Sailmaster.
Its been in my garage for about 20 years.
I replaced it with a Northern Lights Gen. And sold the 39 in 2005.
Great boat wish I still had her.
I now own a 49 Gulfstar.
ATTENTION: I will give the Petter gen to anyone who wants it. It needs repairs but It may be less expensive than replacing. contact me Its in Northern NJ.
Needs to be picked up.

[David Mathis]

We have a 26 year old 9kw Kohler (diesel) with a bazillion hours. It isn't unusual for it to run for two days straight while anchored to run the freezer, refrigerator, ice maker, stove, TV, microwave, and two ac units. A couple years ago the head was removed for a valve job which was a good investment. The cylinders showed no ridge, it was like new. The downside of the Kohler is getting it serviced, they charge for travel plus the hours driven and mileage. We pay twice for travel, plus the parts are getting less available. In a couple years the plan is to remove it over the winter (we're in upstate New York) to have it rebuilt by a local generator shop.



The downside of diesel is the fuel cost. Diesel was always notably cheaper than gasoline but now it's 10-20% more expensive than gasoline.

[Dockhead]

Originally Posted by David Mathis

We have a 26 year old 9kw Kohler (diesel) with a bazillion hours. It isn't unusual for it to run for two days straight while anchored to run the freezer, refrigerator, ice maker, stove, TV, microwave, and two ac units. A couple years ago the head was removed for a valve job which was a good investment. The cylinders showed no ridge, it was like new. The downside of the Kohler is getting it serviced, they charge for travel plus the hours driven and mileage. We pay twice for travel, plus the parts are getting less available. In a couple years the plan is to remove it over the winter (we're in upstate New York) to have it rebuilt by a local generator shop. . .

Sounds like my experience with Kohler heavy duty generator (6.5/8kW EFOZ). Mine has less than a bazillion hours, but it's 22 years old. So far it's never needed anything I couldn't do myself, so haven't had any experience with Kohler service. I try not to run mine for days on end, but I run it whenever I feel like it. It's almost inaudible.

[Stewie12]

For safety reasons, I would carry as little gas as possible.

[cdcorl]

This is simple. Never have gas on board if you can avoid it.