LPG. Good or bad?

Thepipdoc

Thepipdoc

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I'm in the final stages of buying my first boat (Sea Ray 270). It's powered by 2 x Mercriser 4,3 EFI engines which have been converted to run on LPG. The conversion was done by a local reputable installer and it was done from new - 10yrs ago.
My question is - does anyone have any experience of this type of conversion( good or bad) and is it as economical as it should be at £0.45 per litre or does the fact that it's running on LPG make it less efficient? i.e. is it likely to burn more LPG than petrol thereby making the conversion pointless-as far as economics are concerned?
Thanks for any replies.
 
From an automotive perspective, the belief is that LPG delivers 95% of the power of petrol and 95% of the like for like ecconomy (i.e no adjustments made for cost difference).
 
I think general opinion is that, these days, probably not worth doing. I looked in to converting my first petrol boat, and it wasn't worth it.

However if you've bought a boat with the conversion done, you should reap benefits. You'll probably use about 10% more LPG than petrol, but you should still have an effectIve price of around 50 ppl. The other thing is that some conversions didn't include very large LPG tanks, so range very limited.

Major engine failures were also reported, burnt pistons and the like. But if yours has done 10 years, it may well be ok in this rerspect.

As you point out availability is a problem, but if you've got a good supply, and others are in range, then that knocks that con on the head.

All things considered looks like you might have a good 'un.
 
Thanks for the replies so far - I'm really impressed with this forum. The answers I've seen/received are clearly knowledgeable and well considered.
I aspire to be the font of all knowledge in the future so that I can be of benefit to other novices!
 
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Wait for Solitaire or Mr Snelson to reply?

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Or me!!!

Torquay is most likely the last place that will lose LPG as a fuel. The reason? Dr Walter Scott, the champion of LPG powered boat in the UK, keeps his boat there and uses lots of the stuff.

The reason most other installs were removed was simple lack of use.

I had my boat converted and pulled into Dover for a refill. The guy on the fuelling pontoon said I was the only LPG customer in 2 years!!!

Anyway, after 30 hours running on LPG my engine died. Lost compression on 2 cylinders and melted a plug. The engine was old when converted so this could have been an issue, but it is common knowledge that LPG make the engine run hotter.

Having said that. my advise would be to buy the boat. You don't have to pay the conversion costs, LPG supply in your home berth is as near to guaranteed as possible and you will save shed loads in fuel costs.

Just have in the back of your mind that at some point in the future you may need to carry out some work on the engine.
 
I had LPG on a Rinker 260V with a 5.7 Carb V8. The EFI's are MUCH MUCH better on LPG than the carb conversions.... I repeat MUCH better so my experiences are the very worst you'll get.

It was excellent with a couple of provisos -

1) Lots of teething problems, but ok once sorted. As this is an existing kit, then you shouldn't have any of these.
2) Not many filling stations. Assuming that you check that the one you intend to use is likely to be about for a while (and it's been there since day one of LPG so it's possible) then on the south coast there you have a decent chance.

Forget 95% - you will actually lose more like 15% of your power and economy, but with fuel at 46ppl rather than 100+ppl the saving is huge - it may not ever pay back the cost of conversion compared to putting a diesel in, but if the conversion is already done you're laughing. The EFi's will be a lot more efficient on the gas than the carb V8 was.

Also simple way to check fuel consumption with an LPG boat. Fill the boat tank with lpg till it stops.

Run out somewhere on petrol. Switch to LPG and run at a sensible cruising pace noting the speed on a GPS. Do this for an exact period of time - between 15min - half an hour - time it precisely. Switch back to petrol, and come back to the marina and top back up until it stops. You will then know how many litres of LPG you have used, over what time and the speed that yields.....

You can now work out VERY accurately your:-
Cruising speed consumption
Range on LPG in NM
Range on LPG in hours

If it gives you a range of say 20m and one hour that's rubbish and you'll never be happy....

However mine did 4hrs running and a range of 80m on LPG - that was enough for me and I hardly ever used any petrol - therefore it worked very very well for my needs - but I had 160litres of LPG on board - make sure you have the same or more with that size boat or the range will be crud

Also I found that to get the best out of it, you need to seriously advance the ignition - I ended up runnign at 15deg BTDC when I think the engine normally runs at 8deg BTDC - I would have gone even more, but then it wouldn't run under serious power with petrol so I did have to compromise - if your engines have a "knock" sensor you'll be able to run much more advanced and really get the best out of it.

I would say if the boats nice - go for it.
 
But that's hardly the point of buying an LPG boat is it?

The other thing I didn't mention is the weight of the kit.

I had 2 tanks, 1 of 90 litres and 1 of 60 litres. The kit alone, with no fuel in, weighed around 200kgs. This did seriously affect the boats performance. With the tanks full, that's another 100+ kgs so it was like permanently having 3 or 4 passengers on board!!
 
I had one of my boats converted to LPG back in 2001, in LPG's hay day in boating times. Twin 5ltr volvos and 320 ltrs of LPG. £5k for the conversion.
It was brilliant, I had zero problems in the short time I had the boat. 120hrs in 6 months. It ran smoother on LPG than it did petrol. Often heard that you're supposed to start and stop on petrol to keep the carb lubricated and have heard of troubles starting on LPG in the winter. I never ran on petrol unless I had to and never had any troubles starting.

Downside nowadays is availability.
 
Fantastic stuff. Thanks for all the generous replies.
I've just finsished negotiating buying the boat and once I've ran it for a month or two I'll post a message her to let everone know how the LPG boat is behaving.
 
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Also I found that to get the best out of it, you need to seriously advance the ignition - I ended up runnign at 15deg BTDC when I think the engine normally runs at 8deg BTDC

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Out of interest the 4.3EFI has the Thunderbird V ignition system which has MBT spark advance on it. This automatically advances the timing (to try and increase the RPM). This can increase the advance by up to 15 degrees, so I would think the engine will already be making the most of the LPG fuel. And yes it also has a knock sensor.
 
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