which gas?

[shakespear]

have just bought a late 70's early 80's 120 mercruise outfit its in the boat and have test run with unleaded fuel.<br />does this engine need leaded or unleaded as uk goverment have done away with leaded and now use some greener alternative. which have had varing report from an engine recker to ok.<br />As i don't realy want to have to pull the head of and spend 2-300$ puting unleaded vavles and seat in<br />just hope some one has the answer

 

[rolmops]

Re: which gas?

Hello<br />Lead was put in gasoline as an anti foam material.<br />As it turned out it was a big pollutant, which found its way back through the food cycle straight into our systems.That is why it's use is banned in fuels.Unleaded fuels are fine although there are a few problems.It has many more chemicals added to it than leaded fuel.One of the side effects is that unleaded gas tends to get "old" as in "no good" a lot faster. When you use unleaded gas you should add a fuel stabilizer and some say at least an eighty nine octane fuel to make your mix with.<br />Happy boating.

 

[shakespear]

Re: which gas?

Thanks<br />But its not a two stroke, its a four stroke and I thought the lead protected the valve seats from burning out, and so I dont want to put the wrong one in. PLEASE HELP

 

[Franki]

Re: which gas?

Lead is a lubricant.. it lubes the valve guides and valve stems.. (or at least it used to. <br /><br />You can either run a very high two stroke mix, (like 200+:1) or buy one of the additives that achieve the same result, (by doing much the same thing.)<br /><br />If you want to, you can replace the valve stems and guides with hardened jobs that can handle unleaded.. or you can go with one of the new "lead replacement" fuels.. we have a heap of them here now (in Australia) because there are still heaps of cars around that used leaded fuel. The Greener fuels you speak of contain other additives that are supposed to achieve the same result as lead without the negative side effects.. use it, its the best you will find. and if you find that your valve guides get worn, change them, but thats not something that will happen overnight anyway, so I wouldn't worry about it too much.<br /><br />rgds<br /><br />Frank

 

[Boatist]

Re: which gas?

Hello<br />I think I have the same block and head you do. Mine is a OMC 3.0 L. 181 Cubic Inch 140 HP 1980 year. It is a Chev/GM motor. My owners manual says use leaded fuel 87 octain or higher. When they first took the led out of fuel was big worry for me so I checked with OMC factory rep at a San Francisco boat show. He said no need to worry the unleaded fuel would not harm the motor. I ask about additives and his responce was will have no effect and may cause problems if fuel stays in tank for a long while like durning winter. He added if get any pinging to use a higher octain. The lead was to cushion valves and boost octain. Since then I have just used regular fuel. I did have a problem with a exhaust valve in number four cylinder but not from fuel but because I was not smart enough to know when to change exhaust manafold and water leaked in to valve area and valve rusted. When I took the head in again ask guy at head shop to see if it needed hardened valve seats for unleaded fuel. I expected him to say yes and here the price but intead he said should be fine.

 

[Newhook]

Re: which gas?

Not to split hairs but my understanding is that lead as an additive in gas was to lessen engine knock. The lead slowed the combustion and made for better performance and less wear on engine parts. It had nothing to do with foaming to my knowledge.

 

[Forktail]

Re: which gas?

Newhook's on the right track. This scare came out when unleaded fuel was first introduced.<br /><br />Lead was added to gasoline to increase octane. This allowed engine manufacturers in the "old" days to run higher compression engines. Higher octane means the fuel burns slower. And the slower burning fuel eliminates the knock of high compression ignition (fuel ignition timing).<br /><br />Lead did coincidentally end up adding some lubrication, which helped the older engines from wearing out the valve trains.<br /><br />But as we all know, someone discovered lead killed people. So emission standards came in affect. Then the auto makers found that lead destroyed catalytic converters. Oops. Bye-bye lead. <br /><br />Gasoline makers found new additives to put in the unleaded gasoline that were safe, and yey provided the same function of octane and lubrication.<br /><br />By the late 70's and early 80's, most engines were more than capable of running on unleaded fuel. Only extremely old engines were manufactured with "soft" valve seats.<br /><br />So....run the unleaded and relax. Your late 70's early 80's Ford can handle it.