Regular or Unleaded gas?

[lake_time]

Hi, I have a 1977-140hp Johnson and the book says leaded gas. Can I add a lead substitute? Is there any difference between 2 and 4 stroke lead additives?<br /><br />Thanks as always,<br /><br />Dave

 

[ICEMAN]

Re: Regular or Unleaded gas?

Hi Lake_time, You can use unleaded gas in your 1977 outboard. Lead was added to fuel back in those days, it was more important for an inboard motor to use leaded fuel, unleaded fuel used in those motors caused valve problems. The outboard valve system is different and unleaded fuel will not cause you any problems.

 

[ICEMAN]

Re: Regular or Unleaded gas?

Also, The manufacturer does not reccommend using a lead substitute. I have found that when one of my customers has used some of these additives, they have carburetor problems. Some products leave sediment in the carburetors.

 

[lake_time]

Re: Regular or Unleaded gas?

Thanks Iceman.. should I adjust the timing or anything? I have heard stories about new head gaskets for leaded and unleaded.. Any ideas?

 

[ICEMAN]

Re: Regular or Unleaded gas?

Hi Lake_time, The alternative head gasket is for low octane fuel, (Not leaded or unleaded) OMC Part # 332819. According to service bulliten # 2159 Rev. 1 If using pump posted 91 AKI (anti knock index) or higher no modification is necessary. If using 88 AKI spark timing must be retarded 4 degrees. I have found that retarding the timing, especially on a rebuilt motor, makes the motor last longer. Sometimes you don't know what the fuel rating is.