Old Merc. oil/fuel ratio

[Bassy]

Got a 1957 Mercury Mark 55 40 hp. motor. What is the gas/oil ratio?

 

[dilligafda]

Re: Old Merc. oil/fuel ratio

The ratio is 50:1<br /><br />1 pint oil to 6 gallons of gas.

 

[Chinewalker]

Re: Old Merc. oil/fuel ratio

If it were my old Merc, I would richen it up and err on the side of caution. The motor originally called for 24:1 ratio. Modern oils are much better, and the Mercs are better able than their contemporaries at handling a leaner mix, but I wouldn't go all the way to 50:1. Split the difference at 32:1 or 40:1 and you might get another 50-years out of it.<br />- Scott

 

[RICKRICK1]

Re: Old Merc. oil/fuel ratio

Bassy-- My old 56 johnson called for 25 to 1 originally. I talked to my local johnson dealer and he said to run about 32 to one or richer. The motor would run on 50 to 1 but he said the difference in the older dearing area clearences required a richer oil mix.

 

[Bassy]

Re: Old Merc. oil/fuel ratio

Okay,thanks.<br />Bassy

 

[ZmOz]

Re: Old Merc. oil/fuel ratio

Yeah, I run 32:1 in my inline 6. It's not going to hurt anything to run a little extra. It will hurt if you don't have enough. I know from experience...