Basic LPG question

Greenheart

Greenheart

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I was looking at outboards and considering their suitability (and unsuitability) aboard small yachts which are offered with either inboard diesels or outboard auxiliaries...

...and it occurred to me that most people with a modern electricity demand may well also run a small generator on the boat...and then I remembered the stove, requiring propane...so why not plump just for petrol, rather than have an assortment of different fuels?

...so my question is, IS propane very different from the type of LPG which petrol cars (and presumably petrol outboards & generators) can be converted to run on?

Wouldn't it be a handy thing to run your auxiliary, dinghy outboard, generator, heating system and stove, all on the same fuel?
 
I don't know for sure whether the technology has moved on, but I recall that converted engines used to require petrol for starting and therefore also switched back before stopping to prepare the system for the next start. That's OK as a remote gas tank is no more problem than a remote petrol tank, but it would negate one of the advantages of ending up with a fuelless engine to stow in the locker - you'd still have the integral fuel tank. As the calorific density of LPG is lower than petrol you would also need a sizeable tank (one of the problems with some car conversions) and dare I say it, if you run out/low the single fuel source becomes a burden, saving the last drop in case you need it for propulsion; cold, dark and hungry.

I'd love to know if it is now possible, though.

Rob
 
I have a mastercraft which is converted to run on LPG and I know for a fact that doesn't need any petrol. When I first got it it ran on forklift propane bottles and I added a tank myself to run on lpg so it is the same thing. You can even refill the canisters with LPG if you have the right adapters (Although I believe this is illegal so don't recommend)
 
That's very interesting. And, presumably small units like generators could be fuelled the same way, albeit requiring some alteration of the ignition system?

I've heard that petrol engines drink quite a lot more LPG, though it remains an advantage economically. Any idea how many miles per kilo of LPG your boat goes?

Am I right...is propane the same as car-type LPG?
 
yes the propane is exactly the same. I have no idea how many miles as I only use it on a small lake but from what I know it uses slightly more LPG than if it were petrol but not 100% sure.
 
dancrane said:
That's very interesting. And, presumably small units like generators could be fuelled the same way, albeit requiring some alteration of the ignition system?

I've heard that petrol engines drink quite a lot more LPG, though it remains an advantage economically. Any idea how many miles per kilo of LPG your boat goes?

Am I right...is propane the same as car-type LPG?
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The issue is that you cant buy petrol tax fee, LPG you can,
Stu
 
In France a couple of years ago I saw a factory supplied LPG outboard of 6 hp IIRC it was a mercury (must dig out the holiday snaps), but haven't been able to track one down since, Lpg generators are quite popular in some parts.
Its the same propane you would use in your boiler, cooker, car or just about anything else.

PS Lpg fueled engines tend to use only about 10 to 15% more fuel than when running on petrol.
 
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All very encouraging, thanks. And if I understand it, there's no reason why one can't revert to petrol with an LPG-converted engine, if only gasoline is available.

Why isn't everyone using budget LPG this way, instead of costly unleaded?
 
dancrane said:
All very encouraging, thanks. And if I understand it, there's no reason why one can't revert to petrol with an LPG-converted engine, if only gasoline is available.

Why isn't everyone using budget LPG this way, instead of costly unleaded?
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Because the conversion for a small engine is several hundred quid, it takes a long time to get through that much petrol.
Also petrol is convenient, readily available and safer.
 
Rodg98133 said:
yes the propane is exactly the same. .....
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Propane is not exactly the same, 'autogas' lpg is generally a mixture of propane and butane, possibly other stuff too.
Not sure the mixture would be right if you switched to pure propane or butane?
 
dancrane said:
Why isn't everyone using budget LPG this way, instead of costly unleaded?
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Another factor is that to be cost effective you need to be able to buy it from an LPG filling station. You are only allowed to fill fixed, installed, tanks in vehicles. Once you start thinking of Calor in bottles the price advantage disappears. (I guess if really determined you can get into filling bottles from your vehicle, or from your house bulk tank, but......).
 
I'm a bit lost here. Isn't it cost effective, bought in those barely-portable cylinders? What about the biggish gas cans we use in France - probably 30 litres - (very heavy) which my dad uses to fuel his hob at home? And the narrower, much longer cylinders I've seen (though I can't recall where)...must they be returned to an overpriced registered re-filler, rather than filled at a dockside fuel-seller's?

Isn't it possible to (legally) construct a large yet portable canister/cylinder incorporating approved seals such as cars are fitted with, so that we can buy our gas at an approved station then carry it in substantial quantities to the boat? Or, isn't it perfectly possible to fit a large Range Rover-type LPG tank, aboard a yacht?
 
But you started off talking about outboards etc ! Didn't (Calor?) spend a lot of money installing marina filling points a few years ago to persuade mobos to convert ..... only to give up and remove them a few years later?
 
As in post #3 above there is nothing wrong with converting the engine and fitting automotive type LPG tanks, but as usual it all comes down to cost,
If you have a 6 litre yank engine wanting gallons of petrol per minute then your conversion cost will be recovered pretty damn quick,
If you have a 2hp generator costing £200 more than a petrol one then that's going to take quite a bit longer to break even.
 
VicMallows said:
Another factor is that to be cost effective you need to be able to buy it from an LPG filling station. You are only allowed to fill fixed, installed, tanks in vehicles. Once you start thinking of Calor in bottles the price advantage disappears. (I guess if really determined you can get into filling bottles from your vehicle, or from your house bulk tank, but......).
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That's not correct. I have a refillable LPG bottle on my boat. We fill it at the local independent car filling place. We cook with LPG. It is propane. I pay 70p/litre. About half price of calor and it's a see through Kevlar bottle so you always know how much gas you have. The bottle case is plastic so no rust stains on deck. Love it.
 
gas is gas and you can run a engine on any gas
you just have to alter the jet size .
to do a proper convertion cost a fair bit so only really worth it on large inboards
two stokes would need to be oil injection models and the oil would not mist up very well
you can compress natural gas look up CNG
you can start on gas but a lot of the the first simple systems did not have gas chokes so started on petrol
newer gas injection systems run of the exhaust co to get the fuel mixture right so a temp reading can be sent into the ECU
 
dancrane said:
That's very interesting. And, presumably small units like generators could be fuelled the same way, albeit requiring some alteration of the ignition system?

I've heard that petrol engines drink quite a lot more LPG, though it remains an advantage economically. Any idea how many miles per kilo of LPG your boat goes?

Am I right...is propane the same as car-type LPG?
Click to expand...
to replace it. You don't need to mess with the ignition, I had a Honda 4.5kva genny I bought a conversion kit off Calor, Basically take the float chamber off the carb, take off the jet housing, screw in a crude machined tube. A rubber tube was jubilee clipped on to that which led to a large diaphragm regulater which was connected to a propane bottle. The suction of the intake acted thru the tube on the diaphragm which supplied gas, the more gas that was fed to it, the faster it went! The governor regulated the inlet suction pressure which then regulated the regulator. Basically the tube that was screwed in is the only thing that you need plus a reg. Calor charges an arm and a leg for it!
Calor gas propane is an expensive way to go, decanting from home heating tanks is the way to go to make it a cheap option. Or buy it in third world countries where you don't get striped for it!
http://www.petepower.co.uk/LPG-gas-conversion.html
Here for a reg http://www.autogasshop.co.uk/impco-garretson-kn-automatic-prime-863-p.asp
Get one of these, make a spacer to fit between the carb and engine, drill a hole, fit a tube with approx. an eighth inch hole in it, rubber tube it to the reg and carefully experiment!
Stu
 
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