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Seeking small HP engine recommendation

Seeking small HP engine recommendation

Seeking small HP engine recommendation

I need a reliable stationary engine in the 7-8 HP range that can run reliably 24x7 (short downtime for filters, oil changes and basic maintenance excepted) for 17,500 hr (2 yr) between rebuilds.
Cooling: Water cooled preferred
Fuel: NatGas
RPM: 1200-10,000 Range adaptable

That seems to leave a few technologies that might be applicable.

Anyone have any experience or suggestions of a specific engine to consider?

Best regards,

RE: Seeking small HP engine recommendation

You might check what Kohler has in their portfolio. That's a pretty long time between overhauls for a small engine.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Seeking small HP engine recommendation

Hi Lou!
They have several Alt-fuel engines in that range. All air cooled unfortunately.

Going to be an interesting search.


RE: Seeking small HP engine recommendation

You need it to produce 7-8hp around the clock for 17.5k hours? If that is the case, the closest that you'll be able to get is to use an industrial engine that is built to handle 20+ hp at a high duty cycle.

The Kohler Command Pro (CH740NG) is a very over-built industrial engine with a horizontal shaft. I do not imagine it suffering from any metal-fatigue failures with the needs of your application, as it is known to handle very abusive applications for 2,500 hours. Since your application does not sound abusive, I'd imagine this may be able to survive far longer, with relatively normal maintenance.

RE: Seeking small HP engine recommendation


The application is well behaved, bolted down and locked up in its own space.

I should have mentioned my loading profile earlier. I picked ~7HP as that is the ballpark ‘peak’ generator load at 5ish kwe.

During 85% of the time actual load is under 1.8kw and 95% of the time the load is under 4kw. So the load between 4-5Kw would be ~8 hours distributed over 168 hours for any given week.

So the two questions in my mind here:

1. The 740NG is rated at 19.5 HP and this specific load at its peak, will just occasionally load up to a tad more than 1/3 or the engine capacity. So with this lighter loading, is a 66% derating buying significantly more runtime hours or did we pass a point of diminishing returns? (Unit price needs to roll in here to)!

2. If 80% of the run time is loading the 19.5 HP engine at only ~2.5 HP, am I operating this machine at a really poor point on its efficiency curve?

Appreciate everyone’s thoughts and guidance!

Best regards,

RE: Seeking small HP engine recommendation

Yes, efficiency will be poor at such light loading.

Is a combustion engine that's running all the time, the right technical solution? You've told us how much load it may be seeing, but not what it's actually doing, and why it has to be done using a combustion engine running on natural gas instead of (let's say) an electric motor running on grid power.

Maybe my suggestion to use an electric motor will look stupid once you actually explain us what the engine is supposed to be doing and why you can't do it with an electric motor.

RE: Seeking small HP engine recommendation

Hello Brian,

Good points.

The backstory is actually pretty common in a lot of rural areas right now it seems.

Ours got started a couple years ago after a really severe regional ice storm. Preplanning varied a lot. Some people around us were equipped and didn’t miss a beat while others were out for weeks under real hardships keeping their families warm and farm stock alive. Some took some really bad losses that could have been helped greatly with just a little bit of neighborly help. Farm right behind us had a bad go of it and we never knew they were in trouble. Lots of motivation right now to get stuff right. Some just need a Honda and an extension cord … others have some serious skin in the game. I’m just an old fart retired (15yr) eng doing some projects as they pop up trying to be a little useful.

That situation got everybody talking about how to cope with emergency conditions such as short duration local weather outages, regional problems that become extended such as the Texas ERCOT mess or even a, God Forbid, national level problem which could extend weeks to many months. More talk, more people see the holes.

NatGas for fuel is just economical and reliable in the region and avoids liquids issues. In the process of digging around we also found out that local distribution companies are literally out of pole transformers. Their bulk orders from 2020 have yet to be filled. One fellow we know works for a local natgas company. They are running low on simple house regulators. Supply chain issues has everyone on edge a bit.

Good/junk generators are flying off shelves and folks getting them more often than not don’t know where to start. Some ask harder questions as they see further risks. One of the local electricians told me he was swamped putting in transfer switches and was having to hit out of state supply houses to meet schedules. We are more and more on our own each day it seems,


Will post some more tech ideas we discussed tomorrow after a little shuteye.

Hope that helps!

RE: Seeking small HP engine recommendation

Lister is legendary for their low horsepower engines. It appears they have exactly what you are looking for.


RE: Seeking small HP engine recommendation

Recall that the core of the Texas power problem was the loss of the natural gas supply. Water in the gas wells froze and blocked the natural gas supply lines so it could not go to the power plants. It also could not go to homes where people might have cranked up the gas fireplace or stove or the water heaters.

I'd go for a big bank of batteries, an inverter, a large solar cell install, and a big propane tank with a propane fueled generator; sure, have natural gas if it's available to hold off on burning propane. Perhaps a wood pellet stove or furnace as well; I bet someone makes a clockwork feeder you can wind up for several hours of operation before a re-wind is required.

RE: Seeking small HP engine recommendation

Just make sure you allow for some heating of the propane tank for when it gets really really cold....

But why do you want this thing to run continuously for 2 years if you're only using it during a power outage?

Or are you trying to go off (electric) grid altogether?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Seeking small HP engine recommendation

I'd also spend a few hundred bucks on a pull start gasoline powered genny. Sure it is no good 24/7 if everything else is dead, but it'll keep the basics going while you find fuel or do maintenance.


Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Seeking small HP engine recommendation

Whoa! You guys are great!

Tugboat: I had seen a couple antique one lung Lister vids, but I was unaware that there was any current production. My research had turned up a few marine designs like the Marathon LIMA SER 1200rpm head that looks an order of magnitude more solid than most (if you are thinking about being in a isolated situation w no help coming). Great link! Will dig into that!

3DDave: Nailed it. The TX debacle was a predictable, 75% self inflicted cluster. Freeze offs are a national affair every year and the need for field workers to thaw them is never going away, but gas utility mgmt has fired experienced field and eng workers below the labor level needed to reliably run the plant and are not developing replacements. That’s systemic nationwide and total recipe for flippin’ disaster. ALSO, pipes are installing ‘electric’ compressor stations. I used to work for a pipeline many moons ago and I remember the ruckus when mgmt twisted a few electrics on the comp engineers after some marketing boys took the top dogs to the Masters Tourney in Pittsburgh. Talk about chain sawing the wrong side if the limb you are sitting on LOL!

What could possibly go wrong when rolling blackouts choke off gas flowing to natgas fired electric generation stations???

Who could have seen that coming?

I’ll rant-off for now, but one thing you can take to the bank is that parachuted-in corp managers that couldn’t qualify to work for a day in the field are going to freeze and starve many, many more people to death than died in Texas before the negative feedback blowback takes them out.

One of the local guys I met is USAF ret out of the San Diego complex and he bought a 200ac mountain 25 miles deeper in the exurbs than I am. He threw in one of those standby 15kw whole house packages on a pad outside his new quarters. A yr later he had a pc board go bad and it took two months to get it in. A pic he sent me had a dozen surface mounted chips that made it darn near impossible to timely self-repair even if you had all the info, test eq, skills and parts. He casually noted that these would be the first thing cooked in the event of an EMP in advance of a war. Interesting point from a MIC wig that easily could afford to live in any high end gated community in the country.

Your suggestion on batts/inverter is definitely on the table. Our thinking was to add a 24/7 2-4kw DC pony engine/gen floating the batts AND driving the inverter so as to carry 85-90% of his KwH monthly energy requirement without a 10Kw noising up the grounds, wasting fuel, etc. With the batts essentially only for peak catching and gen fails, noise, battery cycles and depth of discharge issues about disappear for the most part an will at least double or triple batt life. Need more info/experience to finesse the battery trade offs.

Inverter reliability/repairability is still an big issue. Throwing a bunch of money at spares probably will be his solution.

Would be interested to hear any inverter mfgr experiences anyone will offer up!

3D/LittleInch: Timing-most of the folks I talk with have a time horizon of short term, weather related power outages, but the number of those seeing a degree of risk of outages lasting months or even years (including me) is growing. Especially see that in newer expats that have moved here in the last couple yr. And, as the old man of the extended family, if things go worst case wrong, I’ll have 9 looking to me for a solution. Freezing grandkids isn’t an option for me.

Here is our energy equation. Up on the Cumberland Plateau we are 80% clouded over Dec-Apr. The cost of extra panels, batts and driving down consumption to where the missus revolts makes solar uncompetitive with alternatives.

Propane is a solid tech solution, but today it is about 1/3 more expensive than resistance heat from the grid. Burying a 1kgal tank opens the smart opportunity to top off when prices drop. It’s a great standby solution for most people, given there is no supply chain issues getting into the state since there is essentially zero production here.

NatGas locally comes from two sources. Interstate pipes and local production. Local production is very attractive for those willing to dig a little deeper into it.

Thanks for all the info! I appreciate the thinking and suggestions!!!

Best regards,

RE: Seeking small HP engine recommendation

I found a US distributor for HawkPower that integrates 6/10.8 Kw heads w Lister-Petter as their prime mover.

I asked for specs, availability, price and lead time.

Interesting. Will pass along what they show up with


RE: Seeking small HP engine recommendation

Fuel cell.

je suis charlie

RE: Seeking small HP engine recommendation


Looks good! Going to check it out.


RE: Seeking small HP engine recommendation

I don't think anything made now is reliable. Keep us posted what you find.

RE: Seeking small HP engine recommendation

That is my big concern.

Gas with percentage points of butane, pentane and longer is my first question about catalyst effects as well as other typical smaller contaminants like sulfur compounds, etc.

The poor ‘celebrity’ track record of Bloom Energy et al has my radar all the way up. Still, it sure would be great to have a couple kw running quietly 24x7 as that’s 85% of my monthly base load KWH and plenty for weather related power out time where activities get scaled back anyway.

So far, the outfit below, is the only one that I have found talking about significant run time history. Looking for their economics/life cycle costs. I dropped them an email, but don’t have a contact yet.



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