Generator Installation Location

[Sailflap]

I'm looking to install an Onan 9kw generator on my 2007 Jeanneau Sun Odyssey 49' (3 cabin layout with the aft starboard stateroom converted to a workshop). The concern I have is that I'm installing the generator slightly to starboard of centerline (next to the inner bulkhead of the workshop) and not along the actual centerline of the boat. The generator weighs roughly 600 pounds. So basically I'm just kind of worried that I'll be putting too much weight on one side of the boat.

To try and offset the weight to starboard I'm moving the house battery bank from the starboard side to the center and port side of the boat. I'm also converting the 3rd water tank (~230 liters) which is located on the starboard side (under the workshop) to an auxiliary fuel tank which will remain empty most of the time.

The factory installed generator is an Onan 4.5kw which fits under a centerline bench in the salon. The 9kw generator will not fix under the bench and is the reason I'm installing it in the workshop.

Thanks!
Brian

[Zanshin]

I have a 2007 49DS and the generator (a Fischer Panda 5000) is located under the sole just forward of the companionway stairs. The location is ideal, it fits perfectly in the centerline and is close to the batteries & main switchboard as well as to existing through hulls. I would have thought that the 49i has the same location preplanned for a genset as well.

Anway, if the items are all at a similar height with respect to the waterline, you can use the same type of simple calculation that is used to figure out weight & balance while flying. Take the weight in pounds times the distance from the centerline in inches, use one sign for port and another for starboard.

e.g..

Weight shifts (Port is positive, Stbd. is negative, inches are distance from centreline):

1. Onan 4.5Kw removed Stbd. = 350Lbs * 24 Inches = +8400inch-lbs
2. New Onan installed Stbd. = 600Lbs * 12 Inches = -7200inch-lbs
3. 4x100Ah Batteries removed Stbd. = 280Lbs * 36 Inches = +10080inch-lbs
4. 4x100Ah Batteries added Port = 280Lbs * 24 Inches = -6720inch-lbs

this scenario would be net 4,560inch-lbs to port.

At least the formula will give you a rough idea of how your centreline balance is affected by weight shifts.

[speciald]

Why do you need the larger genset? The factory spec'd genset will provide ~37.5 amps or about 30 amps at 80% load where you would want to run the genset. 9kw would produce about 75 amps. Stay away from the units that run at 3500rpm like Mastervolt and Fischer Panda.

[Cruisingdad]

Originally Posted by speciald

Why do you need the larger genset? The factory spec'd genset will provide ~37.5 amps or about 30 amps at 80% load where you would want to run the genset. 9kw would produce about 75 amps. Stay away from the units that run at 3500rpm like Mastervolt and Fischer Panda.

Sailflap,

If you have already purchased the unit, then forget what I am about to say, but I agree with Speciald - that is a HUGE genset and you may have an issue getting it to 80% load. It will probably require turning on every electrical item on your boat and running ac's. Just a thought - but diesel's like to be put under a good load. Running them soft is not good for them lo0ng term.

I do not neccessarily agree with his assessment on the Mastervolts or FP's. I have owned both and currently own the MV. They have their place. It is good for those that intend to only periodically use their generator. They are very quiet and the high rpm's helps them to run very smooth. THey also have a very small foot print. However, if you plan on running the generator a lot, and especially every day, you would be better off going with a generator that was a low rpm. I think my MV runs at 3750 - but only uses about a pint an hour depending on the load.

Again, if you have already purchased the generator, just forget what I said.

I believe Zanshin gavev you an awesome post on the install of that generator and has probably answered your question there.

Take care,

- CD

[negrini]

I'd ask same question: why this big unity ? I had MV on previous boat with 2 AC plus all gadgets on board I barely used 70% of its 3.5KVA capacity. I'm right now considering the smaler powerplant from Onan (runs at 2.900 rpm, but it's amazingly quiet and very low vibration) but again, major constrain is it will take a lot of stuffs powered on to reach eficient 80% on power, that I just don't have on board today. In summary, an oversized genset means: lower life span, waste on fuel, weight and space. Think it over if you can.

[Sailflap]

Why so big? I did a lot of research and decided that I wanted to go with an Onan generator. I have a large house bank, AC, watermaker, washer/dryer, etc and wanted something around 7kw. The Onan representative said that the current 6.5kw's were an older model generator and not readily available. He recommended that I wait until the new Onan 6.5kw's came available in Feb 2010. This time frame won't work from me as I trying to get this installed before leaving the UK for the US soon. The 9kw was the next choice but I really don't want the extra weight of the larger generator. I'm leaning toward the 5kw and just adjusting my "concurrent" power requirements.

[Sequitur]

I am delighted with my choice of a Fischer-Panda 4kW DC generator in my Hunter 49. Because its output is DC, not AC, it doesn't have to run at a set rpm to produce 60Hz, and it is very quiet. The 1225 Ah house bank seems to like talking directly to the generator, which adjusts its output to the load. My 2800W Magnum pure sine wave inverter supplies proper AC for the washer/dryer and for any other AC that I need.

[negrini]

Brian, I think Michael took a beter approach. Even using all the gadgets you mention, I doubt it will drain that power dealer is suggesting. Have you done your power balance to find out how many amps you really need ? How many amps is it ?

[cebretko]

I have a NextGen 5.5 on my 2003 S.O. 45.2. It is more than adequate. It is reliable and runs at 1200 rpm. I located the unit under the cockpit sole between the twin helms in the storage locker which puts the unit aft and directly on the centerline. I recommend this NextGen unit and location if your 49 is similarly configured.