# Fuel mixture Question



## Gumby (Mar 5, 2011)

I just bought a 1957 7.5hp Evinrude. 

What fuel mixture do I run?
Do I use high octane, Additives etc?

I am not afraid to use good stuff to keep it running good.


----------



## crazymanme2 (Mar 5, 2011)

I'd run that motor at 40:1 with reg fuel.


----------



## Bobg (Mar 5, 2011)

With the oil designed for todays two strokes, I used a 50:1 mix in a 55' Evinrude 5 hp with no problems. We're not using the 30 weight non detergent oils any more.


----------



## crazymanme2 (Mar 5, 2011)

You have to remember that most of the older outboards don't use needle bearings as in the newer ones.I also know of people that run 50:1 in the older outboards but I look at it this way,you can't ruin a motor with too much oil.(within reason)


----------



## freetofish (Mar 5, 2011)

It would also be a good idea to find fuel with as little ethonal as possible in it.


----------



## flintcreek (Mar 5, 2011)

The 57 model has the babit bearings and should be ran on a 25:1 mix. This will smoke a little more, but the motor will hold up and last you a long time. Used to when you bought a new motor you ran it on 25:1 fuel mix during the break in period. My local mechanic here recommends running 25:1 when ever you buy any motor that has been sitting for some time. Good Luck.

Flintcreek


----------



## Pappy (Mar 5, 2011)

Lots of folks have apparently been listening to alot of old wives' tales! That engine must be run on 24:1 fuel/oil mixture, as per the manufacturers directions. That is a plain bearing engine and plain bearing engines have to have the extra oil. You will not foul plugs. The ones that recommend less oil are the ones that will not be around when your engine loses crankcase pressures and vacuums from worn piston skirts and cylinder walls and possibly a rod through the side of the block. Extra oil will also promote better sealing, more horsepower (through better sealing) less carbon as the piston can transfer heat to the cylinder walls faster and thus will run below the temps that hard carbon or coking develops. When OMC developed engines that ran on a 50:1 mix or variable ratio oiling (VRO) they also developed pistons with more silicon in them or high sil pistons plus, in some engines, a cam-ground piston. These pistons are much harder and were designed to minimize wear with less oil. Your engine was in production long before those developments came about. If still in doubt, do a little research on Gordon Jennings, the Godfather of two-stroke development. He absolutely lays waste to lean oil mixtures and ran controlled testing to back that up versus someone who knows someone who knows someone who ran 50:1 in their vintage, non-replaceable engine, and got away with it!


----------



## po1 (Mar 5, 2011)

I agree at the min run 24:1. The following from https://www.evinrude.com/en-CA/Owners-Center/FAQ/OilAndFuel#qst2
What is the fuel/oil mix for my motor?
- The following is generally true: 1958 and prior used 20:1, 1959 thru 1963 used 24:1, 1964 and newer use 50:1.
- What grade of fuel should I use in my motor?
Current recommendations are to use a minimum of 87 octane, 89 octane is preferred. There is no additional benefit from using higher-octane fuels, in fact they may cause hard starting conditions in hot weather. 

The 61 5.5hp johnson in my family's been ran on 24:1 for five generations and still run's perfect. I know alot of people run 32:1 and 40:1 because TC-W3 is much better than oils were in the 50s and 60s. It is just a question of how much better and how loose your old engine is and if it's worth going against what the manufacture recommends?


----------



## ray55classic (Mar 11, 2011)

Trust the guys that built the motor, OMC says 24 to 1 .


----------



## wasilvers (Mar 11, 2011)

ray55classic said:


> Trust the guys that built the motor, OMC says 24 to 1 .



Ditto that, a little smoke never hurt anything -in fact, I'd be worried if i didn't see smoke!


----------



## MattR (Mar 12, 2011)

po1 said:


> - What grade of fuel should I use in my motor?
> Current recommendations are to use a minimum of 87 octane, 89 octane is preferred. There is no additional benefit from using higher-octane fuels, in fact they may cause hard starting conditions in hot weather.



Running a higher octane in my area DOES have a benefit. At least in my area of WI, the premium fuel does NOT have ethanol. I always ran 87 octane before ethanol was added and no problems. 

Running 24:1 is recommended. A little extra oil is cheaper than rebuilding.


Matt


----------

