Converting small petrol generator to run on bottled gas

Yes you can, but it would need a complete knowledge of how to with your particular motor...

Some motor manufacturers do supply converting kits, but I would think you would need to do more than just tweak the timing etc...

John.

Hi Horace,

A worthy goal, easily acheived... sort of.

I did a google search on "converting B&S engines to propane," and if you do so, you'll get loads of ideas. Of course, you would not want to use propane, because is can accumulate in your boat, possibly causing everything to go boom. But the principal is the same for CNG, which is much safer for marine use (because it will go up rather than down).

This link will give you some ideas. If your engine is different than one for which you can find the conversion parts, you can usually press ahead, anyway. Although you may need to make adapter plates to match up port sizes, these generator engines are not terribly fussy about mixture control, intake track length, etc: in other words, it is unlike your car, in which mixture is controlled very very closely to meet emissions requirements, and where the injection system for a 2.0 liter brand X will not work well on a 2.0 liter brand Y.

Years ago, for fun, I made a lawn mower engine run on propane from a hand held propane torch. I'd removed the carburetor completely, and waved the torch around in the air, using the valve in the torch to adjust the mixture (in addition to changing distances). I had a friend (equally crazy) to help get it started, and we throttled it with a putty knife. Smoke, backfires, coughing, unstable speed... but running , nevertheless. I think you may want something a bit more sophisticated -- but the parts are easy to find because there are loads of such engines that have been converted.

Have fun, Ken

Ken.

Thanks for your help.

My boat has a propane gas supply for cooking & heating so it is not a problem to connect a short hose to a portable engine - or even use a small gas bottle. I just want to avoid carrying petrol. I could use diesel but they are big and heavy and pricey.

The generator is only required for emergencies for battery charging or running a mini chainsaw.

I will investigate the ideas given in your link. Excellent.

7heating

You DO know don't you that propane is at least as hazardous in a boat bilge as 'petol'.

Hi Blink. About 40% of cars in the Netherlands use propane as fuel, and you can buy conversion kits in the UK for petrol powered engines. If you have a diesel engine, which I suspect you have in your narrow boat then forget it! I won't go into this particular problem other than to say that the laws of physics will not allow you to convert a diesel engine to run on gas. Another thing that you should be wary of is that you may live up to your handle, if you try to do this! If you want to go into technical details why it cannot be done, then I will gladly explain it to you.

Hi Scapolie:

Actually, it is not I who wants to do the conversion. Horace talks of a portable generator, not a diesel propulsion engine. The vast majority of such generators are spark ignition, and in his case, his response to me indicates that this is the case with his generator, as well. Otherwise, he would certainly have said: "Oh wait, you misunderstand -- I have a diesel generator." While using propane in a boat makes me uneasy, because it can collect in the bilge, I have nevertheless done just that many times with boats that rely on propane for both refrigeration and cooking. As far as converting a small generator engine to propane (or the better alternative, from a safety standpoint, CNG) it is simple and done all the time. If you cannot believe that, then I'd suggest contacting some of the many vendors of conversion kits to explain, to them, the folly of their businesses.

If Horace already has diesel propulsion, then the common solution is to simply run the propulsion engine (in neutral if need be) to charge the batteries, and to then use an inverter to supply AC needs. I can't imagine anyone in his right mind considering converting a diesel engine in a boat to propane -- it's incomprehensible, because you give up a principal advantage of diesel fuel over petrol -- namely that it is much safer in marine use, due to its lower vapor pressure. Pour some liquid propane, some petrol, and some diesel fuel in the ground. Watch what happens. Make your own conclusions.

Why on earth would you think he would want to convert a diesel to propane?

His original question was "What is required to make a petrol engine to run on gas?" 99% of all people of even a slightly technical bent interpret "petrol engine" to mean a spark ignition engine, not a compression ignition engine. In fact, it is possible to make a diesel engine run (poorly) on petrol, and fairly well on alcohols, vegetable oils, mineral oils, and a great many gases, including CNG, LNG, propane, etc.

You might want to cruise the web, and learn some physics, if you truly think that a compression engine cannot be made to run on a gas. Here's a quote from one site, but there are hundreds of others:

Diesels work even better, are more powerful and much, much cleaner when they run on compressed natural gas. Truckers love CNG.

But CNG is not available everywhere as it started to be just a few years ago. And CNG's comparative price per gallon to gasoline currently in California is under $2.00 per gallon.

And that's buying it at a gas station. Using your CNG from your home gas supply would be even cheaper.

When you open up an engine that has been running on CNG at 100,00 or 200,000 miles, you find an engine that is much cleaner, has less wear, (pistons, rings, valves) and in better shape than if it had been running on diesel fuel.

Interestingly enough, your country is known throughout the world for having done some impressive engineering. Perhaps your schooling in physics was done elsewhere? What physics were you taught that lead you to say "the laws of physics will not allow you to convert a diesel engine to run on gas."

I am anxiously awaiting your explanation of the physics at work. Certainly, other engineers here will be interested as well -- especially combustion engineers, who believe themselves to have accomplished such things, but who will appreciate being brought back into reality.

Diesel engines of all sizes run on gas all the time. It is very common for stationary diesels to run on NG, but small ones can and do also.

Now now... Ken and Greg, I have the greatest admiration for your contributions on CR4 but Scapolie is a relative newcomer and just missed a sentence or two in the question.

Nothing new to us all eh?

No need to haul Scapolie over the coals for a small error.

John.

Gas conversion of diesel is actually rather common. It does require the injectors being replaced with spark plugs; and you need to use hardened valve seats and 'racing' quality pistons, at minimum they require a very high heat tolerance and usually a thicker crown. Sharp edges like those found in heron head engines with swirl chamber in the piston, need to be removed. Gas doesn't cool the chamber like petrol does as it is already a vapour, consequently the piston runs much hotter, often they crack. for little generators it is just a matter of placing a regulator output pipe into the engine inlet just past the throttle plate, connect the throttle linkage to the regulatot control. job finished.

CNG is still heavier than air so will also blow the boat up. Best get a solar panel and a couple of fork lift batteries!

Actually, the main reason CNG is considered "safer" on boats, and LP consider "less safe" has to do with density. Here's what Wikipedia has to say:

Natural gas can also be hazardous to life and property through an explosion. Natural gas is lighter than air, and so tends to dissipate into the atmosphere. But when natural gas is confined, such as within a house, gas concentrations can reach explosive mixtures and, if ignited, result in blasts that could destroy buildings. Methane has a lower explosive limit of 5% in air, and an upper explosive limit of 15%.

Explosive concerns with compressed natural gas used in vehicles are almost non-existent, due to the escaping nature of the gas, and the need to maintain concentrations between 5% and 15% to trigger explosions.

But it's a minor point. I strongly agree with your solar panel and fork lift battery recommendation. On many sailboats, this arrangement can serve both house electrical and propulsion needs, very adequately. (Obviously not if you have mile after mile to travel with no wind.)

In the small city I grew up in the power plant used huge diesel engines. When natural gas became available they fed the same engines natural gas with just enough diesel in the injectors to produce ignition, Conversion kits are availble for diesel engines to enable a combined propane/natural gas and diesel fuel mix, the majority of the power is provided by the gas but the diesel oil is required for ignition.

In converting to bottled gas, be prepared to de-rate the generator output by as much as 20%.

If you are looking in the range of 3 kW or up, why not get a small diesel generator?

http://apple.clickandbuild.com/cnb/shop/lionsun?op=catalogue-products-null&prodCategoryID=2

http://www.fischerpanda.com/press.htm

http://www.dieselgeneratorsportable.com/#4%20KW%20single%20phase%20closed%20frame%20sound%20attenuated%20quiet%20genset%20remote%20start%20option

If you have propane on board I am sure you know the dangers already and have a detector system in place. Regards small engines it is possible to put a hot tap into the intake manifold before the carburetor this is supplied by a demand regulator which will deliver more or less gas as the venturi action takes place when the carburetor valve is opened. If it is only a small engine gas straight from the cylinders may be OK but if demand is excessive cylinders will freeze and you will have to look into liquid propane supply with an evaporator similar to motor vehicle's

Thanks Garth

Gas installations in narrowboats in the UK are governed by law as part of the Boat Safety Scheme (BSS) in turn requiring a mandatory certificate issued by an independent surveyor after the appropriate pressure and leak tests have been successfully carried out.

That does not prevent you turning the cooker on without lighting it. So a leak detector is a good idea. It is on the list of 'to do' jobs.

For the moment I will follow up the earlier link to engine component suppliers.

Thanks.

Very wise

Would have thought your stove allready had thermacouple sensors on the burners?

In a boat I would make sure that I had propane detectors in the low spots like the bilges.

<>I have seen propane and natural gas conversion kits for diesel engines. The propane/NG is introduced with the air that is compressed in the cylinders and then just enough diesel fuel is injected to ensure combustion.

I lived in a small city in Saskatchewan back in the 50's and 60's. When natural gas became available they converted the massive diesel engines at the power plant to use a mixture of diesel fuel and natural gas. If I remember correctly from a boy scout or class tour they said that the fuel mixture was 96% natural gas and 4% diesel for ignition.