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Old 14 February 2003, 09:13   #1
Country: UK - England
Town: Edenbridge
Boat name: Scorpion
Make: Scorpion 8.5mtr
Length: 8m +
Engine: 315hp Yanmar Diesel
Join Date: Aug 2002
Posts: 696

Just out of interest has any one here concidered using LPG gas instead of spending a fortune of petrol, has any one had the conversion and how does it perform etc.


Julian Lyas
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Old 14 February 2003, 10:00   #2
Country: UK - Scotland
Boat name: Yes
Make: Assorted
Length: <
Engine: 8m
Join Date: Dec 2002
Posts: 110
Similar question just posed by Grumpy1 (?ex flanker? ?ex......?) over on ybw's motor boat forum, several general answers also relevant to Ribs.

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Old 14 February 2003, 10:15   #3
Country: Canada
Town: Newfoundland
Length: no boat
Join Date: May 2000
Posts: 2,097
Yes thought of it

main problems were a) no conversions available for 4 stroke outboards in this country although a couple of years ago Honda were supposed to be looking at it b) couldnt do 2 stroke at all and c) more fundamentally where do you put the tanks? They are pressurised and when installed on a cruiser need to have the container they are in "draining" to outside air in case of rupture or spillage. Problem is that ideal place in a rib is underdeck so how do you vent them? Also they are quite bulky for their size. You could put them under a bench seat or locker on deck but they would take up a lot of room. Got no further than that really but the appeal of 36p per litre fuel really did appeal. Perhaps when the duty exemption finally goes on red diesel there will be a resurge of interest and these problems will be addressed!!

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Old 14 February 2003, 15:43   #4
Country: UK - England
Town: Blackpool
Boat name: To Exi
Make: new sib 4 man
Length: 8+ft
Engine: Mariner 4hp long shaft
Join Date: Nov 2002
Posts: 1,012
Even when you loose the diesel red benefit then a diesel still produces aprox 18hp of raw power out of a gallon and petrol can only produce around 12hp of raw power out of a gallon of juice.

Therfore even with no red tax benefit a diesel still will give you aprox 25% more in economy/power than a petrol when at the same price.The downside being weight.

There is a ballancing act here,in that if you have a light boat it can be more efficient to have a 4 stroke petrol.The problem comes with offshore size and weight,as the more offshore/weight you go the more the difference in fuel burn is and a noticible increase in fuel economy.

I have allowed for a bit of Slippige here as it is a very complex subject as its down to expected use and weight and availability.
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Old 15 February 2003, 19:15   #5
Country: UK - England
Boat name: Won't get Fooled Again
Make: Ribtec
Length: 6.5
Engine: Honda 130
Join Date: Mar 2002
Posts: 888
I thought about this and looked into it quite carefully for the Camel. The calorific content of LPG is about 15% less than petrol.

You need to fit the tanks which are seriously pressurised somewhere on the limited space of the boat. I would have needed about the size of a large calor gas tank or the fuel tanks they use on hot air baloons.

The cost of a conversion was going to be at least 2.5 k and as I didnt think I'd be keping the boat for more than three years it didn't represent Value for Money to me.

I then remembered that the Harbour masters at Hamble had a couple of boats which were running LPG outboards so I went to have a chat with them and they told me they dropped them after about 6 months as they weren't happy. it seems to work well however for big inboards.

Of all the outboard I guess the Honda's are the easiest to convert as they use the lumps from the car engines, I think the 90 is the Civic lump and the 130 is the Honda accord. as they are converted car engines it should be easyish to fit the injector rails made for the relevant car engine. then all you need is to find somewhere to put a highly pressurised canister of very explosive gas. Not for me I am afraid.

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Old 15 February 2003, 19:20   #6
Country: UK - England
Town: Blackpool
Boat name: To Exi
Make: new sib 4 man
Length: 8+ft
Engine: Mariner 4hp long shaft
Join Date: Nov 2002
Posts: 1,012
Nore me Honda will not warrant there engines on gas,and you cant put them on efi engines,its a none starter.they have also shut down a lot of gas filling stations on the south coast due to small take up and limited demand.

There is talk of Honda bringing out a Gas engine but I would presume its when we all go on gas at the pumps,which may be a long time away.
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Old 16 February 2003, 01:58   #7
Country: UK - England
Town: St Mawes
Boat name: Magellan Zulu
Make: Ribcraft
Length: 7m +
Engine: 2 x Suzuki DF150
MMSI: 235094135
Join Date: Dec 2001
Posts: 483
Back from the Indian Ocean. Reading this thread and seeing WAVEHUMPER aboard prompts a quick question.

When are you going to move that engine outta my garage, Stuart ol' chap? No big deal, but it would be nice to get old Landrover inside from time to time again.

Actually, this thread is an opportune place to talk about my close scrape with an exploding engines.

At the end of the week's diving from the Maldivian liveaboard - a 4-story wood and fibreglass streamlined monstrosity made in the islands - we left and the new punters moved aboard.

Next day, miles from anywhere the engine does up in a sheet of flame. The divers jump over board (well, the would, wouldn't they?) and the liveaboard sinks to the bottom of the oggin.

Close shave , or what? Could have spoilt what was a fab holiday for Diana and me. Guess it did for those who followed in our wake.

Glad to be back. Cheers for now....
Mike G
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Old 16 February 2003, 06:57   #8
Country: UK - Scotland
Make: HumberOceanOffshore
Length: 8m +
Engine: Volvo KAD300/DPX
Join Date: Oct 2002
Posts: 4,851

Mike, which fuel tap did you forget to close?

Just joking

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Old 01 October 2003, 16:33   #9
Country: UK - England
Town: Leamington Spa
Boat name: Whizzpopper
Make: Humber
Length: 5.5m
Engine: Mariner 75ELPT
Join Date: Sep 2003
Posts: 16

Not sure that storage is the problem its made out to be, you can get a lot of gas under pressure in to a cylinder; they take a fair knocking about in cars, trucks etc. A cylinder along the base of the transom? Or maybe fill the tubes with LPG.....................!

A company called Marine Gas Solutions say they will be displaying a converted Mercury 115 at the London Boat Show. Whether it would be a suitable RIB installation they couldn't say at this stage.

Take your fire exstinguisher and have a look!

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