Gas conversion

[AndyT]

Has anyone out there had a gas conversion on their boat or know of anyone that has, I am considering having my Searay 28 done as the 7.4l 330hp v8 can be a tad thirsty. Have heard rumours that the engine will burn more gas per hour than it would petrol, sounds rubbish to me but i aint no mechanic. Also any other advise or problems that may be associated with a conversion.The engine is eight years old but has only done 180 hours

 

[tr7v8]

General experience is that gas consumption is higher per litre. This is because of 2 reasons 1. Gas has a lower calorific content than unleaded and 2. because the means of getting it into the engine is compromised because you wish to keep a petrol option. Gas however has a much higher octane rating circa 112 rather than the low 90's as is standard unleaded. This means if you make ignition changes then you can run masses of ignition advance and get back most of the lost power.

Jim
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[AndyT]

Thanks for the info,is the consumption of gas as opposed petrol significant? I heard that you may use up to twice as much gas per hour as you would petrol making the saving on fuel less atractive and therefore hardly worth the initial cost of the conversion

 

[tr7v8]

No not twice as much, figure bandied around is 10-15%.

Jim
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[oldgit]

Before you spend a single euro check the search facility on this forum for recent posts on gas coversions.
Personal opinion is keep boat as is and consider smelly old oil burner during next purchase.( will be one, like it or not.)

O my Gawd its still going ahead......

 

[cngarrod]

Am considering the same... so have done a bit of reviewing... !

MBM does an annual report on whether this is a good idea or not, the usual responses and concerns regarding explosions and all that... but to be fair, from what i have seen there is no greater risk with LPG as there is with normal Petrol.

Reading a review of my boat (Falcon 23) there was an owner that had done the conversion and said that it uses about 20% more LPG in comparison to Petrol - but thsi still makes the savings quite significant.

I would guess the biggest issue is the availability of the fuel, and the continued availability of the fuel.

There have been a couple of horror stories on here abotu converted boats (in terms of reliability more than anything else, althought rectifying and fault responsibility comes into it too i think), might be worth discussing this with a few that have had it done...

Agree with Oldgit - do a search for previous threads and poss speak to Kim Hollamby to see what issue had the LPG report in it (was earlier this year)

Also agree with oldgit when he says get an oil burner next time... well we probably all want one eventually, but the price for a diesel now means that i wouldn't have the boat in the first place!

Good luck and let me know how you get on.

Cheers,

Craig.

 

[oldgit]

Regarding the price of diesel boats.Boats are out there at the right price but you have to go looking.I paid 15% less for my Princess 33 diesel boat than the price asked by some of the Thames brokers for similar petrol craft.
Best to search around coastal locations, not up river areas which are stuffed full of petrol boats.
However for river work the petrol boat is just as good as cheaper to buy in first place.


O my Gawd its still going ahead......

 

[airbubble]

Hi, here in the NL we're very used to not only cars, but also the V8's in boat running perfectly on LPG. All wakeboard/ski boats use it, otherwise nobody can afford boarding. They all use twin portable tanks, just like forck-lift trucks. Not all roadside filling stations like you filling the portable tanks though. For the engine's (mostly the 5.7 litre version of the one you have) it's no trouble, don't bother to change valve seats etc like in some cars. To make the installlation more simple, we normally do away with using unleaded altogether. You will use 20 % + more of the stuff, but roadside price makes it still very very worthwile. Specially under heavier load, it will use even more gas. When normally wakeboarding, we run about 1,5 hr on one portable tank (± 30l) but like last week, when we had the wakeboard cup, so boats were fully loaded with waterballast, jury and a cameraman, we only did 3/4 of an hr per tank. The only thing you have to get used to is when switching from one tank to another is to slowly open the valve, otherwise the gas expands too quickly, freezing the fuel supply, leaves you dead in the water for half an hour.
Don't know about installation costs over there as the kits are widely available here.
We always recommend people doing it. Success.

 

[adarcy]

airbubble
I always thought it was advised to start and shut down using petrol in an LPG conversion, something about easier to start on petrol vapour and protecting the carb gaskets.
Do you mean that you run your engines on LPG only and never petrol?

 

[CJN]

If it works like that great!! personally without any safety systems on board etc I wouldn't be on the same lake as you! In the uk I believe the cop18 comes into practise, under the LPGA. Even Mastercraft boats are not installed correctly and the people I've spoken to seem to have problems with setup etc. Why cut corners on your safety and the safety of others

 

[CJN]

You can run a boat dedicated LPG if you want to, ski boats on a lake not a problem. I wouln't advice a sea going vessel to be dedicated, if there is a problem with LPG you always have back up fuel. If you have the correct safety systems on board under the cop18 LPGA, then if there is a problem with LPG, exhaust gases, any hydrocarbon in the engine bay. the alarms will tell you and shut of the LPG, safety!!
Starting a vessel from stone cold is simply easier on petrol, get some heat in the block and then change over, either tied up or in gear. Starting on a warm engine on LPG is not a problem. All MPI engine should start on petrol, just like a LPG car!

 

[CJN]

AndyT, The consideration is where to mount the LPG tank(s) does your boat have any room in front of the engine, or either side. Water tanks, waste tanks etc may need resiting. You need to have the boat surveyed for space etc. Shouldn't be a problem. What engine is in the boat Merc or volve. (normally Merc) If Merc then it will have a Rochester carb, if volvo may have a 4 barrel holly, need to find out. 4 Barrell hollys on a 7.4 are a problem, but can be got over.
As for consumption, you will use more LPG than petrol, but not a great amount. What you will find is the owners of LPG boats cruise faster thatn they use too!!! thus burning more fuel.Your engine at 3300rpm will do 12 gallons an hour, depending on how clean her bum is etc etc, can burn on the stops, 27 / 30 gallons an hour!!
Ring Calor Gasand ask for the brochure on Ian Hollisters 37 foot Sunseeker, he has 2x 7.4 Volvo with 4 B-holly's
Hope this helps

 

[adarcy]

Re: MPI

Dear CJN
Thank you for confirming my understanding that cars on LPG are started on petrol and I fully understand why cars ( with the occasional scarcity of LPG fuelling points) and a boat on a lake not needing asecond fuel source. I certainly would keep petrol on standby on a river or offshore boat.

Could you please expand on <<All MPI engine should start on petrol, just like a LPG car! >>, do you mean Multi Point Injection? If so, why? Do you mean any petrol based engine with an injection pump, whether single or multi point (although I accept single points getting rarer) because the pump needs lubrication whereas carburettors don't? In which case, do cars with carbs not need a petrol start?
Sorry if this seems pedantic, but I just don't understand the difference.

 

[airbubble]

Hi, indeed, we never use petrol anymore with the correct/mastercrafts. Twin portable tanks, despite boat being open, er vent always on when masterswitch is on; certified hoses, careful installation; safe enough in my eyes (and I am a certified and MCA approved surveyor..)
We never had any trouble. knock wood.
The system is a bit different from a car's system, but i have to be honest here that I never exactly understood how both car and these systems work. We have 'em installed by a car-LPG conversion specialist who knows about boats also.It's sort of a direct injection system, hence you do not need the heat a conventional car system does to vaporize the lpg, that's why it used to be recommended to start on petrol with a car, specially on cold mornings. New car systems, they're called G-3 over here and have all kinds of environmental tax-benefits, use a similar setup.
I can try to find out or have tech specs drawn up a bit more in detail should you be really interested in the technical side. try a car lpg specialist in the UK first for the direct-injection type systems however i would say. KR

 

[airbubble]

Re: MPI

see my other reply, more in general. The old systems needed the heat to vaporize lpg.
With multi- or single point injection that need is gone, that's the main reason.
kr

 

[neale]

I would put any conversion plans on hold for the time being.

Marine Gas Services who are the only real marine conversion specialists have pulled out of the market as of 16/08.

Details are sparse but watch this space.

 

[KevB]

I haven't read any of the other replies so I may be repeating what others have already said.

I had my last boat converted to LPG, twin 5ltr V8's. The boat ran very smooth on LPG (even better than on petrol) and as far as the running was concerned could not have been better. It started on the button every time even in winter. The down side to the conversion was firstly the cruising rang, I had two LPG tanks installed giving a total of 220 ltrs, this only allowed for about three hours cruising unless you were prepared to switch back to petrol and watch your money being guzzled at the rate of 90 ish pence per litre. The second down side is finding somewhere to refuel and the amount of time it takes, although there are around 30 LPG suppliers on the south coast they are never where you require them so refuelling takes a lot of planning and, refuelling takes soooooo long as I believe the pumps are similar to what is used in petrol forecourts and only designed for the amounts you'd expect to put in your average family car.

If I was in the position of having a petrol boat now I would probably have it converted to diesel rather than LPG, I know the cost is probably three times as much but the convenience of diesel is worth it. And you can't compare the cost of LPG per litre to that of petrol or diesel, as LPG is at least 20%less efficient that petrol and petrol is at least 20% less efficient than diesel, that’s a whopping 40% difference between LPG and diesel. This is a fact so don't believe the adverts when they compare the running cost to diesel. LPG is a better option than petrol if you can put up with limited range and supply but does not come any where near the cost and convenience of running a diesel boat.

IMHO If you do a lot of boating invest in diesel rather than LPG. I have already been there, seen it and done it and now own a diesel boat. Twin KAD 43's with diesel @ 24p a litre, 9 gallons an hour cruising total = cheap boating.

Of course this may change in 2007!!

 

[Xenopus]

We're just in the process of getting our second boat converted - the previous one had a 5L V8 and behaved beautifully. Once the timing was altered we lost no discernable performance or range (to our pleasant surprise) and the boat was certainly happier running on LPG than petrol - the cost savings were enormous despite the temptation to open the throttle at any opportunity. Our experiences were only positive and my recommendation would be to go for it without hesitation. With the new much larger beast we considered a diesel conversion but we want to hang onto her for a while and felt that we're getting too close to 2007 (or whenever we harmonise taxes with Europe) to risk that amount of money for potentially little gain.

Enjoy the boat whatever your decision!!