Mercruiser 5.7. Which Petrol?

[syd]

Hi all,
Could someone tell me if a 1990 Mercruiser 5.7 V8 engine would normally run on unleaded please, or do they have to have additives and can they run on LPG.
Many thanks
Syd

 

[Col]

This engine is a marinised Chevy,as it's American,they have been built with hardened valve seats for years,so unleaded no probs.Lpg is an easy convertion,there are a number of companies offering this service.I would check on the location of fuelling stations near you first.

 

[Guest]

Some questions !
1) I would be interested in knowing how much it would cost to convert an engine of this type to use LPG ? Any ideas ?

2) Do you get a new tank for LPG and retain the existing one for petrol ?

3) Also, I have heard that you get about the same performance and full consumption as with petrol. Can anyone validate this please ?

 

[KevB]

Worlock,

I had my boat converted to LPG this April and found it to be excellent. If you are on the South coast the fuel is readily available at something like 20+ marinas, I think there are more LPG fuel stations then petrol along the south coast.

The performance is almost equal to petrol with only a reduction of a knot or two in top speed being the difference.

The beauty of LPG is when you start the engines (I have 2 x 5.0ltr) there are no fumes or smoke and it runs smoother than on petrol. I can have the engines in gear ticking over at only 400 rpm, this allows for incredibly slow manoeuvring.

The installation of the LPG tanks depends on the space available on your boat, I was fortunate to have plenty of space in the engine compartment therefore had the tanks installed there (about 220 ltrs in total).
The tanks are always cylindrical due to them being slightly above atmospheric pressure (2 bar I think). I have retained both my petrol tanks.

As part of the installation, sensor are fitted in various locations within the boat to detect if their should be a gas leak, as all the valves on the LPG tanks are electronic should a leak occur the tanks are sealed automatically.

The price for my conversion was slightly under £5000 for both engines and two LPG tanks carrying a total of 220 ltrs of LPG, I think the price for a single engine conversion is around £3000.

I have worked out I need to refill about 40 times with LPG @30p per ltr to re coop my initial outlay from then on I'm in pocket. I have refilled about 22 times so far this season.

The only drawback I have come across it the limited range (about 3 hours cruising) before having to refill, obviously the bigger the tanks the further the cruising range. They can fit additional tanks in all sorts of places if you have the space.

Would I do it again: Most definitely. Although the initial outlay of £5000 was a lot of money I do not have to worry now about using the boat as the running costs are not that far off diesel. I guess when you consider petrol engines are far less expensive to service and they are not prone to dying from under use, LPG conversions are a good bet for the petrol engined boat user.

If your interested in seeing a conversion my boat is in Chichester Marina

Who knows, by 2007 all the diesel users will be converting to petrol and LPG????

Hope this helps.

 

[Guest]

Hey ! Thanks for the detailed reply. I appreciate it very much.
I am looking to buy a used single petrol engined boat and I think the LPG conversion is a great idea. At £3000 it is cheaper than splashing out on a diesal engined boat and i can see LPG becoming much more popular. I shall probably be moored in a marina at or between Poole and Southampton, so it sounds like it wont be a problem getting the LPG. I shall obviously check this out before paying the marina fees. I thought your comment about 2007 was interesting and something i have thought about myself !!
Can you still run on LPG AND Petrol ? Is there a fuel system switch that allows you to keep some petrol as an emergency means of fuel ?
Thanks once again.

 

[KevB]

Worlock,

No problem with switching from LPG to petrol and back again you do it with the engines running. What you get is a three position rocker switch, LPG-Off-Petrol,
If your running on petrol and want to switch to gas, flick the switch into the off position and wait for the revs to rise., basically your emptying the carb float chambers of petrol. When the revs start to rise the engines are running leaner (running out of petrol) when this happens switch to LPG which takes over instantly.
Switching back the other way is a matter of flicking the switch from LPG to Petrol.
I have 2 engines and 2 switches which if I wanted to allows me to run one engine on gas and the other on petrol.

Try www.calorgas.co.uk they list all the marinas that sell LPG. To give you a bit more incentive to convert to LPG they are offering 12 months interest free credit on the conversion.

Calorgas have shares in a company called Marine Gas Services, this is a franchise which train engineers on how to do the conversions, I guess it's the equivalent of CORGI. Marine Gas Services are insurance company approved, having the conversion done has not effected my insurance.
IMHO definitely money well spent.

 

[nealeb]

Kev

Read your post with interest. What boat do you have?

Neale

 

[KevB]

Neale,

It's an American sports cruiser called Tiara S2 310sc, they don't import into the UK so not heard of over here. 32' ish with a 12' beam I think?
Your welcome to have a look if your considering a LPG conversion.
The boat is in Chichester marina.

Kevin