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Old 25 October 2004, 19:13   #1
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Unleaded Fuel

I just thought of this and have no idea what the answer should be.

Okay you can only buy unleaded fuel now. Unleaded came in as a statutory requirement in 1992.

Since then engines in cars have had a cat and all been able to take unleaded fuel.

My understanding is that engines in cars pre 1992 had to have their iginition modified by the dealer or take LRP (Lead Replacement Petrol).

However no where have I seen questions raised about outboards.

There are a lot of old outboards being used out on the sea.

Where do I satnd with my pre 1986 Outboard. Do i need to take some precautions or because it is two stroke do I just ignore them. Indeed does it effect me?

Any body know ??????
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Old 25 October 2004, 20:45   #2
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The main purpose of lead in petrol was to cushion the blows of a valve against a cylinder head - cast iron heads are the main problem as they tend not to have hardened valve seats - alloy heads always do as the alloy is too soft on it's own.

2 strokes don't usually have normal poppet type valves but have ports that are uncovered by the piston as it goes up and down - hence no need for the lead.
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Old 26 October 2004, 04:48   #3
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Timing

Quote:
Originally Posted by Biggles
My understanding is that engines in cars pre 1992 had to have their iginition modified by the dealer or take LRP (Lead Replacement Petrol).

However no where have I seen questions raised about outboards.

?

Any body know ??????
Hi Biggles,

No need to worry about timing as outboards are designed to run on pretty low octane petrol anyway.
Shell Optimax / old 4 star = 98
LRP = 97
Unleaded / old 2 star = 95

I think, and stand to be corrected, that most outboards can run on about 92 octane.
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Old 26 October 2004, 05:20   #4
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Quote:
Originally Posted by codprawn
The main purpose of lead in petrol was to cushion the blows of a valve against a cylinder....
No it wasn't. Tetra Ethyl Lead was added as an knock inhibitor/octane booster but it was also found to provide protection in the very high temperature areas. In valves and valve seats, I reckon it was probably absorbed into the surface of the metal.

Lead is also added to steel to make it free machining. It comes away softly and smoothly with little tendency to snag or pick up.
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Old 26 October 2004, 06:37   #5
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Quote:
Originally Posted by jwalker
No it wasn't. Tetra Ethyl Lead was added as an knock inhibitor/octane booster but it was also found to provide protection in the very high temperature areas. In valves and valve seats, I reckon it was probably absorbed into the surface of the metal.

Lead is also added to steel to make it free machining. It comes away softly and smoothly with little tendency to snag or pick up.
Agreed when FIRST used this was the purpose - as octane ratings go up it becomes more and more necessary but these days not so crucial as our petrol is all crap!!!
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