[Amel Yacht Owners] Generator load, carbon buildup, etc.


eric freedman
 

Craig,

My Onan is a MDKAV model and I don’t have the slightest idea how many rpm the 3 cylinder Kubota is running at. However it puts out 220-230 volts at 50 cycles.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Saturday, March 17, 2018 10:40 AM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Generator load, carbon buildup, etc.

 

 

Hi Eric,

Sorry, didn't mean to sound cheeky. I think your Onan has the same Kubota 3 cylinder engine as my Northern Lights, but whereas mine operates at 1800 rpm (I've got it set for 60 Hz 110v) I see the spec on the Cummins Onan says it operates at 2900 RPM (that's the Onan QD 6/7.5/8 KW Generator that seems to be their current model). I think I just stepped out of my knowledge level - how do they get 50Hz at 2900 rpm?

Cheers, Craig SN#68



---In amelyachtowners@..., <kimberlite@...> wrote :

Craig,

Of course the generator does not have a variable speed.

What I meant is that we usually do not run the genset under enough load.

80 percent of the output of a 7.5 kw genset, I believe should be a usage of about 27 amps.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...
Sent: Friday, March 16, 2018 9:49 AM
To: amelyachtowners@...
Subject: RE: [Amel Yacht Owners] Black Smoke From Volvo Penta Engine Exhaust

 

 

 

Hi Eric,

You bring up an interesting point when you say you had the same carbon build up problem in your genset exhaust elbow, caused by not running at high enough rpm's. Unless you've got a variable speed genset, it always will be running at a high rpm (3000 or 3600 depending on Hertz), so rpm may not be the only issue. Isn't it low load that's the issue? 

So when Yanmar says to run the engine way up, no doubt they're assuming it will be in gear and will present a full load from the propeller. I think the genset analogy would be to load it with not just battery charging, but also get the Admiral to run her hair dryer, make toast, wash clothes and iron your shorts. Not a bad regimen, actually.

Sound about right?

Cheers, Craig SN#68 Sangaris

---In amelyachtowners@..., <kimberlite@...> wrote :

Hi,

I had his problem with my genset. It is caused by not running a diesel at about 80% of its redline. Diesels like to work hard. Our diesels are not run that hard so is the main engine.

Yanmar suggests to run the engine way up. In my case 3000 rpm for 15 minutes  a few time a day

This blows the carbon out of the turbo and the exhaust system.

 

 

The carbon is usually glass hard.

However if the elbow is not perforated due to corrosion, I would try  to break out the carbon.

You might try something like a dremel tool with a hard steel bit, or even better a carbide bit ,or a small cutoff disk. Being that they have ordered a new elbow for you,  you could go Medieval” on the elbow.

 

On eBay there is a fellow that makes beautiful Yanmar elbows out of stainless steel. They are much better than the factory unit. Possibly he makes elbows for your engine.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 


pstas2003 <no_reply@...>
 

Good day to all,

For those of you who are fairly new to their boats and are not completely sure that the previous owner ran their generators at the proper load or whether that is effective enough, I would urge you to take the time to remove your Onan exhaust elbow and inspect for carbon build up.

We purchased our SM a little over a year ago.  The previous owners were adamant with me to always run the Onan with a high load when they generously spent four weeks with me during the purchase transfer/training period, and I adhered to this regimen.

A few weeks ago, the generator started acting up.  At first, it would not handle a full load, then, it would not run at all.

When I inspected the exhaust elbow, I found it was about 75% clogged with carbon, and the exit port on the exhaust manifold was nearly 100% clogged.  I was hopeful that cleaning both the manifold and elbow would solve our problem, but it was too late.  The back pressure from the exhaust must have broken some of the piston rings as only one of the 3 cylinders had compression that met specs.

This was an unnecessary early death for unit that only had 3300 hours on it.  I read on the forum about another owner who found similar deposits at only 2000 hours, allthough I believe he was able to save his. 

We could rebuild the engine, but we have decided to replace the whole unit instead and remove major components for spares.  We are going to do the work in Martinique as soon as the new unit arrives.

Checking the elbow was on my ‘todo’ list, but too far down to get to in time.

As the previous owners were insistent that the unit be run at high load, I’m not sure if this is a case of them not always practicing what they preached, or if the design is just prone to clogging.  For this reason I urge you all who may be unsure of current conditions to do an inspection.  I am planning on checking the new one after every 500 hours or so until I can acquire enough empirical data.

All the best,

Paul Stascavage
SM #466 - s/v Rita Kathryn
Rodney Bay Marina


Craig Briggs
 

Hi Eric,
I googled the spec sheet on your MDKAV and it says it runs at 1500 rpm. It's the newer model that runs at 2900 rpm. I should think a variable speed would be great at it would always present a full load to the engine, regardless of rpm.  Oh well, next boat.
Cheers, Craig


---In amelyachtowners@..., <kimberlite@...> wrote :

Craig,

My Onan is a MDKAV model and I don’t have the slightest idea how many rpm the 3 cylinder Kubota is running at. However it puts out 220-230 volts at 50 cycles.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376