Fuel type for 1970's Merc 500's

[joblo33]

I have a few (one less every time I go out on the lake it seems ) running merc 500's from the early 70's and I've always used regular car gas with 50:1 in it. A while ago someone told me I should be runing better fuel because these motors are used to leaded fuel. Is this true? Should I be using high octane?

 

[achris]

Re: Fuel type for 1970's Merc 500's

Eric,<br /><br />The 'lead' in fuel was to protect the valves and valve seats in 4 strokes. 2 strokes don't have valves and thus don't have a requirement for lead in their fuel. You shouldn't have any problems running regular gas. Just be sure the engine is propped to the upper end of the recommended rev range.<br /><br />Chris.............

 

[Dunaruna]

Re: Fuel type for 1970's Merc 500's

It would seem that you have answered your own question. 30 year old motor running on garden variety standard gas. Why try and fix what ain't broke.<br /><br />Stick with the regular IMO.<br /><br />Aldo

 

[joblo33]

Re: Fuel type for 1970's Merc 500's

Thanks

 

[Clams Canino]

Re: Fuel type for 1970's Merc 500's

And make sure the max advance is 34-35 degrees BTDC. And decarb the things - often at first.<br /><br />Carbs clean?<br /><br />-W

 

[joblo33]

Re: Fuel type for 1970's Merc 500's

The one I'm using right now has *kinda* clean carbs. They work at high speeds but it can be tough to get there. I'll clean 'em when I get a spare moment. Right now it's camping/fishing season and I don't want to mess with what works.

 

[achris]

Re: Fuel type for 1970's Merc 500's

Sounds like the prop may be a tad too big.