Onan Generators-typical ‘life’

[Peterlewis321]

Morning,
Am curious to know people’s experience with the Onan generator, reasonable life expectancy (when properly maintained) and so on. We have a 7KvA unit on our boat and it has done c900 hours since the boat was built in 2011…..we use the generator quite a lot in the summer (aircon etc) but I have no real feel as to whether the 900 hours is high for a boat our age and whether it is likely to crap out at 1k, or 5k, or 10k hours etc etc (we do get it properly/fully serviced every year).
Second from the boat propulsion systems failing it is the fear of the generator not working that keeps me awake some nights!!!
Thanks

 

[volvopaul]

Morning,
Am curious to know people’s experience with the Onan generator, reasonable life expectancy (when properly maintained) and so on. We have a 7KvA unit on our boat and it has done c900 hours since the boat was built in 2011…..we use the generator quite a lot in the summer (aircon etc) but I have no real feel as to whether the 900 hours is high for a boat our age and whether it is likely to crap out at 1k, or 5k, or 10k hours etc etc (we do get it properly/fully serviced every year).
Second from the boat propulsion systems failing it is the fear of the generator not working that keeps me awake some nights!!!
Thanks

The med boats count up thousands of hours , I just find the onan units eat impellers so they need regular attention

 

[Peterlewis321]

The med boats count up thousands of hours , I just find the onan units eat impellers so they need regular attention

Thanks Paul-good to know. We replace our impeller every year regardless of condition and so probably the max hours each impeller sees is 100-150 maximum.

 

[Forty_Two]

I have a 2002 11KvA Onan with similar hours. I consider it just run-in. Have had two oil pressure sensors fail (showing inconsistant pressure), replaced the raw water pump due to some corrosion & replaced the heat exchanger last year as had trouble sealing an end cap.

I stripped out the disintegrating foam sound proofing stuff inside the box & replaced it with proper foil faced sound proofing material last year.

I carry a comprehensive set of spares including all pumps, hoses, heat exchanger, regulator & all sensors.

Feel completely confident it will outlast me, top tier product.

 

[Hurricane]

The med boats count up thousands of hours , I just find the onan units eat impellers so they need regular attention

Paul
I don't actually use the generator as much as most Med boats.
But I've found that this Jabsco impeller (being made from neoprene rather than rubber) lasts longer than the official Cummins ones.
18948-0001B JABSCO IMPELLER
Cheaper as well.
People will probably argue that I should be using the branded parts but this impeller fits my Onan generator and certainly lasts longer.

 

[Hurricane]

The other big issue with Onan generators is that after about 7 years, the heat exchangers seem to fur up/ become blocked.
I bought a spare heat exchanger, swaped it out and then cleaned the old one up.

This is what happened to my old heat exchanger after about 9 years



I used an acid wash to clean it and then flushed it thoroughly.
I haven't actually replaced it yet - the generator is running on the new/replacement one at the moment.

The only other problem that I've had with the generator is the raw water pressure switch that detects that the raw is water flowing.
On mine it was fitted between rubber pipework and was subject to corrosion (only the pressure switch itself was corroded).
See here:-


I noticed that Onan had fitted the pressure switch to the replacement heat exchanger.
This has the effect of including the pressure switch in the galvanic circuit thus protecting it with the generator's anode.
So, moving the pressure switch to the heat exchanger seems to have worked for me.
I'm no expert but, for right or wrong, thats what I've done.

 

[Portofino]

I can’t seem to access the hrs data on my MASE air cooled Yanmar 400 cc single air cooled powered tiny 3.5 .
It gets used almost every day for about an hr .I recharge the batts after 4/5 hrs @ anchor .Primarily to maintain there health , something along the lines of trying never letting them drop [ X ] % .Some say “ X “ is around 50 ? Dunno ?
One of the fridges feels a little voltage sensitive and stops I suspect too soon as the volts drop anyhow .

The geny itself has had a new Johnson pump ( £170: complete unit ) as I had trouble getting it to seal .Bearing shaft weeped let air in and drained it .PITA having to re prime it .

The pump ,pumps seawater through a heat exchanger , bit like a small car rad which cools the air which is fanned across the engine fins , bit like a air cooled bike motor .There is no Fwds wind so to speak so it creates a breeze of cool air .
So no conventional HE like Hurricanes above pics to foul up .
New anode on the water air exchanger every year and that’s about it .

Carry spare impellers , last week out of boredom I changed it , well took the face plate off for a inspection as I had all the covers off anyhow to inspect it .It looked fine .Anyhow opened up a new one as the old was at least 4 yrs .
It went in , but I could not get it to draw water , continue to draw after re priming the system .You get a change in note of the exhaust so immediately know when the waters stopped flowing .Plus I could touch the faceplate , feel it warming up and also touch ( carefully with spit on my finger ) the exhaust manifold which is SSteel btw , it starts to get hot as well .
No leaks what so ever round the pump .
So I swapped the old one back in and hey presto back to normal .
I guess the new one was a fraction different width or something?? , not pressing up enough on the face plate - dunno , a duffer .
Anyhow bought two more @ €12 each in the Marina shop .

Like Forty two ^^^ I have a few years ago totally replaced the sound insulation inside the box covers with a thicker lead linked auto insulation, adhesive + bolted up .That worked a treat reducing the noise .
We have used it this year when returning to port to power up the Aircon , chill the interior down .
When on shore power @ the dock after tying up I just flick the 3 way switch from geny to shore and the system never notices .
Then turn the geny off after a minute.Book says let them cool down ( windings ) after a load .

Anyhow I do waxoil none inert metal components and spray WD 40 around it , the fins etc once a year .
It won’t die .
Its belt was from a citreon AX €4 , I have a spare and starter motor is a VW Polo the 995 cc 3 cylinder so I read ?

Previous to this I had a Fisher Panda on another boat and that just fell apart in a marine environment.Constantly breaking down and bits corroding .I hear they have improved but not for me .No Thx ,

Theses little MASE , I think they air cool up to 7 or 9 Kv before going to conventional HE and water jacketed engine blocks has been reliable .
If I was in the market I would get another air cooled one , it’s just eliminates all this SW HE hassle and coolant water jacketed engine issues , thermostats , Head gaskets , corrosion potentially and over heats .It’s hard to overheat a air cooled finned cylinder head . My 0.02 p

 

[vas]

PF, my 8-9kW MASE is definitely water-cooled (yanmar 2GMF) I think only the smallest ones (3-4kW) are air-cooled

V.

 

[ARE]

900hrs is barely run in, I have a lot of Onan experience and it is not unusual in commercial application to see 25,000hrs plus. The most important thing is to use the generator. They need to run regularly with a good load (75%) at least every 3 months and of course regular servicing with good quality 15W40 mineral engine oil.

 

[Hurricane]

900hrs is barely run in, I have a lot of Onan experience and it is not unusual in commercial application to see 25,000hrs plus. The most important thing is to use the generator. They need to run regularly with a good load (75%) at least every 3 months and of course regular servicing with good quality 15W40 mineral engine oil.

Please see my post above with the blocked heat exchanger.
Having had that kind of blockage, is there anywhere else I should look/clean.
The exhaust is a Halyard system like this:-

 

[MapisM]

This is what happened to my old heat exchanger after about 9 years

M, you'd better fit the BodgeFlow, I reckon!

 

[Hurricane]

M, you'd better fit the BodgeFlow, I reckon!

Thats why I wanted ARE's comments.

 

[Peterlewis321]

900hrs is barely run in, I have a lot of Onan experience and it is not unusual in commercial application to see 25,000hrs plus. The most important thing is to use the generator. They need to run regularly with a good load (75%) at least every 3 months and of course regular servicing with good quality 15W40 mineral engine oil.

Thanks that is really good to hear….its funny I see adverts for boats a few years old stating generator hours of like 150 or something…..and I think, we run ours all night and a decent part of the day so call it an average 15 hours per day…..which based on a 3 week holiday in the med in august would be c300 hours per year so makes me wonder how these units can be such low hours!!!

 

[jrudge]

Thousands and thousands of hours.

My gen runs for days at a time from dock to dock. I have a gyro so it has to be on. Bonus is aircon.
Don’t worry about hours. I have done 200 in the last 4 weeks

 

[DAW]

Thanks that is really good to hear….its funny I see adverts for boats a few years old stating generator hours of like 150 or something…..and I think, we run ours all night and a decent part of the day so call it an average 15 hours per day…..which based on a 3 week holiday in the med in august would be c300 hours per year so makes me wonder how these units can be such low hours!!!

Low generator hours on boats in the Med are straightforward to explain ... Lots of boats are used mostly as day boats. A typical day out is 1-2 hours each way and 4-6 hours at anchor. There is no problem with drain on the batteries and before the arrival of stabilisers the only reason to run the generator was power for the ice-maker, cockpit fridges, etc. Most people didn't bother and preferred to enjoy the anchorage in peace, so it's common for the generator to have similar hours to the engines, or often less.

Since the arrival of stabilisers (whether fins or gyro) everything has changed. If the boat is equipped with stabilisers, you will use them almost all the time when underway and at anchor and for this you need to run the generator. You get the added bonus of constant a/c, etc. and once used to this, most people I know continue to run the generator when underway. My current boat has fins and even though we use it predominantly as a day boat, after two years the generator has multiple times the hours of the engines.

Agree with the comments above on Onan generators. The generator itself seems well designed and bulletproof. Its quiet, easy to maintain and service and I would have no concerns about long-term reliability.

 

[ARE]

Please see my post above with the blocked heat exchanger.
Having had that kind of blockage, is there anywhere else I should look/clean.
The exhaust is a Halyard system like this:-
View attachment 120269

The only other maintenance that needs doing is valve clearance every 1000hrs and I would recommend cleaning (yearly) or replacing the anti syphon valve if fitted. You should also descale/clean out the exhaust spray head as these can get blocked causing overheating.

 

[Hurricane]

The only other maintenance that needs doing is valve clearance every 1000hrs and I would recommend cleaning (yearly) or replacing the anti syphon valve if fitted. You should also descale/clean out the exhaust spray head as these can get blocked causing overheating.

Are there any notes or diagrams on the exhaust spray head that you know about?

 

[ARE]

Are there any notes or diagrams on the exhaust spray head that you know about?

Here is a picture of the assembly on an Onan 13.5 to 19kW. Item 7 is the spray head. You can unbolt it and soak in Rydlyme. I always replace the gasket as well.

 

[Hurricane]

Here is a picture of the assembly on an Onan 13.5 to 19kW. Item 7 is the spray head. You can unbolt it and soak in Rydlyme. I always replace the gasket as well.View attachment 120366

Thanks

 

[25931]

That was a surprise. When I saw the title of this thread I thought that it was about wankers.