Helia 44: MAJOR TIP: Cummins Onan Impeller Problems....

[Helia 44]

Hello Friends,
And obvious Connoisseurs of fine Catamarans in Fountaine Pajot..

Here is a MAJOR TIP... Problems with the Cummins Onan salt water pump impellers...

THE ANSWER: There are none....

I am maybe the just about only one to have personally owned a Helia 44 with a 9 kva Cummins Onan, and now the Saba 50 with the 11 kva Cummins Onan. The problem with the impeller is not a Cummins Onan problem...


The problem is they are often mounted like in the Helia and the Saba, far above the waterline for good reason, but from new the impeller runs dry until it sucks up water.. This kills it and it starts dropping vanes on the impeller in less than 100 hours. The problem is not with the Cummins Onan, it is the most tough reliable simple Kubota tractor engine run generator, the problem is not Cummins Onan, the problem is in the installation..

THE FIX: Look it is simple, and it is a relay driven water pump down at waterline by the thru hull. When you start the Cummins Onan, there is a 10 second priming time, blower comes on, diesel prime pump comes on, and a simple relay firing up this salt water pump gets water up to the impeller IMMEDIATELY.. This is what should happen.. Pictures of mine below...

HELLO FOUNTAINE PAJOT, THIS IS FOR YOU: I am told by one of your French Reps here in the southern hemisphere you watch my Threads like on the Improvements to the Helia 44, and now this Thread Improvements to the SABA 50.. I see some of my ideas in the Saona 47, so yes I do believe you watch these threads.. Because of this I will put this post in the Thread "Improvements in the Saba 50" so you see it.. You should put this in from new, in the installations it should be done. It gives Cummins Onan a black eye, and when vanes run off the impeller from running dry, they clog up in the heat exchanger and cause even more work... A simple relay driven water pump at the thru hull that comes on with the prime and blower solves a serious defect.. That is not even Cummins Onan's fault..

In the pictures below, you can see my relay driven water pump, down on the hull. It comes on before the engine starts, in that 10 second prime time delay before the engine starts. Any strong 12v pump will do, this is a fairly small one, the one on my Helia 44 was larger. Both are upgrades to the installation that SOLVES the impeller problems...


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One more tip for you Connoisseurs of fine Catamarans, Look, the anode in the heat exchanger sheds material, and it slows the flow of salt water in heat exchanger. I had a steaming exhaust, sign of over heating, that ended up in shutting down the Cummin Onan Kubota engine on high temperature. No worries for the Kubota tractor engine, they are almost bullet proof. But at 450 hours or so, I replace the impeller when there was nothing wrong with it but I had it open, then I replaced the Thermostat, which was fine but I had to remove engine housings to get to it, and the simple fix was an acid wash out of a bucket, to clean the heat exchanger. You just disconnect the line at the thru hull and put the 4 to 1 water to acid mix in the bucket, and run it for like 15 seconds, shut it off for 10 minutes and run it again. I did this a few times with ten liters of the proper heat exchanger acid mix watered down. Run for a about 15-20 seconds, shut is down 5 to 10 minutes to cook the calcium, lime, anode bits, and anything else out of the heat exchanger, and now She is Sweet as...

You can tell because in the picture below showing you my pump and salt water strainer, before I cooked it out like the Professionals do it, the salt water in the strainer was only a minor gushing flow. Afterwards, it was a roaring gusher flow, like about three times as much.

I learned how to do this from the Professionals, and that is how they clean the heat exchangers. Just get the RIGHT acid mix, from them, in your area. Then it is a simple job sort of every 400-500 hours, or every time you change the anode in the heat exchanger. The exchanger clogs up with calcium, lime and the anode bits that disintegrate and restricts the flow and this is a regular maintenance issue...

Now I can run a full season, year, or 200 hours to an oil change, and THEN change the impeller too.. If you hear the whine that they Cummins Onan has impeller problems, it does not, it is a dry running impeller problem on the installation.. !!! The Cummins Onan is big, easy to work on, Kubota tractor engine run, very robust, and is the pick of the litter of all the generators available because of its large size and robust drive system..

Kind regards from Steve, Helia 44, now Blessed to be on a SABA 50 that BTW is easier to sail as it is not as reactive to the seas being so bloody big... It intimidated me with its size, and now? I am in love..

[Octopus]

Not sure if the impeller is the same on our 16.5kVA Onan genset, but we had a similar issue with Onan impellers disintegrating prematurely. We solved it by switching to Jabsco impellers, which seem to last more than 10 times as long, 2000 hours being the record.

[Thalas]

I'm curious on your feedback on the size of these generators. These days, it seems pretty easy to get 1200w+ of solar on the 45/47/50. With Lithium prices dropping, could you get by with an Onan 5kw gen for AC/Compressor/Water and the occasional battery top off? The 5kw is literally HALF the weight of the 9kw. I would also imagine the smaller size of the 5kw makes maintenance around it easier with more space since I know some of these larger generators are packed within an inch of their life.

Anyway, wanted to hear your comments since I'm just an armchair sailor on this particular topic.

[Captain Bill]

Why don't you use a 120/240v air conditioning pump instead and just plug it into the 120/240v (which ever you are running). When the genset starts producing AC the pump starts automatically. The water flow sensor is on a 30 second time delay so there is plenty of time for the flow to start before the computer shuts the genset down. I solved the problem of short lived impellers just by installing a check valve in the intake line which prevents the water from running back down to sea level and the impeller never ran dry. It was lots cheaper than your solution.

[Simi 60]

16.5kva is a huge genset.
What on earth could you have on 42ft to warrant that?

[Helia 44]

OK,
Great, a few questions here.....

Captain Bill: I don't run the air conditioning most of the time. I suppose it could be done to run off the ac salt water pump, but I would rather this dedicated pump just for the Gen Set...

Simi 60: One word answer, NOTHING. It that is not a miss print nothing would warrant such a huge Cummins Onan.. That or he is running a boat with all 240 volt cooking and everything? Crazy, and no...

Thalas: I have a great answer for you that will make perfect sense once you consider three things....
Air conditioning
Air conditioning
and wait for it.... Air conditioning...

Look, at anchor in the semi-tropics, I cannot sleep during a really hot spell of sort of 42 C degrees at night and flop all around.. In fact not over 30 degrees do I get a good nights sleep... I tried once in the Helia 44. It was the peak of summer over the Christmas vacation behind the famous Fraser Island in a hot spell of 42 degree days and 30C+ at night. Summer here is sort of Dec-Feb in the Southern Hemisphere.. Trying to be conservative, trying not to put excessive hours on my Cummins Onan, trying to be Green and not burn diesel.. Anyway after about nine nights of poor to nil sleep I turned it on.. I have grown up now and realize at 67 y.o. I am not going to LIVE long enough to wear out my Cummins Onan, and the diesel is cheap!! I mean even on this one at 480 hours, five years old, it is probably a 10,000 hour tractor motor gen set... LOL...

Now, if you are thinking just charging and making water, maybe ok, but I would not muck around. Even then, a 9 kva is only running at about half the load and will last and run better than a 5 kva running flat out fully loaded..

Now my Company has put about maybe 200+ big LIthium battery and charging systems on the road in the Outback, and yes that is appealing. However, you need a LOT of solar on a boat because most of the time it is partially shaded by the rig... Flexible solar panels are inefficient and do not last well, so solid panels are good, but again while I run air conditioning off of my Lithium sets, you need massive input to charge them back up if you want to do it again the next day or night..

I also have full laundry and dryer, ice maker, four frige/freezer sets, and more that is hard to run on Lithium and solar. You could do it with a 5 kva, but why bother? The 9 kva allows you air conditioning break in the heat of the day or on a really hot night.. My Helia had 4 CruiseAire units, my Saba has 7... Look, I have never run more than three with guests on the Helia, and never more than 4 with the Saba 50, but......

I also have over 1000 AH of Euro AGM batteries in my house bank. I would go Lithium, when they get tired, but that is for weight, and charging efficiency. Probably 3-300 AH Lithiums, or 2-400 AH Lithiums in two banks as they are about 50% more power and half the charging time, and, and and...

So, Thalas, depends where you are going. If it is the Tropics or Semi-Tropics it is all about your age and Lifestyle.. I love having my laundry aboard. I love the AC break. I love a big freezer... I love my ice maker in really hot weather.. I love my YK3 water maker for unlimited water... I love my two Victron Charger/Inverters, one 2500watt and one 3000watt. I have done it tough and this is much better.. It is the difference between camping out and roughing it, and making a comfortable Lifestyle of it.. Really, that is the answer... Myself, I think the 9 kva is the minimum.

Kind regards, Steve, Single Handling the Saba 50 in the GBR, Whitsunday Islands, Queensland Australia
And for fun a few pictures of my "treasures" from beach combing... This is all from the past two months of beach combing....

[Captain Bill]

My point was not to use your current air conditioner pump, but a 120v or 240v Alternating Current pump run from your Alternating current side of your genset. Such pumps are pretty cheap and used for air conditioner cooling water pumps. They also last a very long time. They are constant speed and can be chosen to match the requirements of your genset. Since genset raw water pumps are also constant speed choosing the right pump is just a question of matching the outputs at the same head pressure.

[a64pilot]

Originally Posted by Captain Bill

Why don't you use a 120/240v air conditioning pump instead and just plug it into the 120/240v (which ever you are running). When the genset starts producing AC the pump starts automatically. The water flow sensor is on a 30 second time delay so there is plenty of time for the flow to start before the computer shuts the genset down. I solved the problem of short lived impellers just by installing a check valve in the intake line which prevents the water from running back down to sea level and the impeller never ran dry. It was lots cheaper than your solution.

That is exactly what I did on my little Nexgen, at first start it’s sounds loud for about 3 or 4 sec, then the water hits and quietens it down.
There are however I believe other advantages, first when you shut down AC power is off well before the engine actually stops so the exhaust system, muffler etc is blown clear of water, so water lock is much less likely to happen.
Secondly with an AC electric water pump, you can crank the motor all you want, you can’t overfill the exhaust system with water, cause water flow doesn’t begin until after power is present, and that doesn’t happen until the engine is up to speed.
Then thirdly as you suggest the March pump I used almost certainly has a longer life span than the generator, think of how many years they run on boats in Marina’s running nearly 24 hours a day, 7 days a week.
I saw no reason to keep the impeller pump as at best it’s a PIA maintenance item, so I deleted it. Using an electric pump to prime the impeller pump isn’t required, the electric pump can do it by itself.

I’m not a Cat, but I don’t see the difference, any decent pump will have enough head pressure.

[Octopus]

Hi Simi

Mine is a hybrid diesel electric catamaran, so the 16.5kVA gender provides all the propulsion power.

Originally Posted by Simi 60

16.5kva is a huge genset.
What on earth could you have on 42ft to warrant that?

[Octopus]

Originally Posted by Helia 44

Simi 60: One word answer, NOTHING. It that is not a miss print nothing would warrant such a huge Cummins Onan.. That or he is running a boat with all 240 volt cooking and everything? Crazy, and no...
.

"NOTHING” within your experience, but you clearly have no experience of Lagoon's hybrid diesel electric catamaran. The 16.5kVA Onan generator (driven by a 27 HP Kubota diesel) connected to twin 10kW electric motors provides all the propulsion power, which, incidentally, comes close to matching the thrust provided by twin conventional 40HP Yanmar.

[Helia 44]

Originally Posted by Captain Bill

My point was not to use your current air conditioner pump, but a 120v or 240v Alternating Current pump run from your Alternating current side of your genset. Such pumps are pretty cheap and used for air conditioner cooling water pumps. They also last a very long time. They are constant speed and can be chosen to match the requirements of your genset. Since genset raw water pumps are also constant speed choosing the right pump is just a question of matching the outputs at the same head pressure.

Captain Bill,
No disrespect intended, but I want a 12volt pump to accomplish this task because of how the Cummins Onans are set up.. There is about a 5-10 second delay, when the blower comes on, and when the electric priming fuel delivery pump comes on, before the Gen-Set starts. THAT delay is in 12 volt, and easy to tap into with a relay that runs a 12 VOLT salt water pump. Impellers are cheap, and I change mine with the season or maybe 150 hour oil change, and without that prime I was losing impeller vanes now and then... Now? The last one I looked at showed no wear. I will still change them but now they have an unknown life expectancy. It is that "priming" period that I want the pump to deliver water to the vanes of the salt water pump to avoid it running dry. It works, it solved all the wear problems, on the Helia 44 9 kva and now the Saba 50 11 kva and the point of this whole thread is it should be part of any installation...

Kind regards, Steve, Single Handling Skipper and mad inventor on the Saba..