1958 Johnson 7.5 Fuel Mix Ratio

[JDusza]

Hi. Hopefully quick.
I've got a 1958 Johnson 7.5 ready to go. The fuel tank indicates a 16:1 mix ratio.
Is that still the correct ratio with today's two stroke oils?
Thanks,
J

 

[racerone]

Use 24:1 in that fine motor.

 

[JDusza]

Thank you!
J

 

[jimmbo]

Looking at a Parts list for that Motor, it shows No Antifriction Bearings. It doesn't even have replaceable Friction Bearings.

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1958&hp=7.5&model=AD-12&manufacturer=Johnson&section=POWERHEAD+GROUP

Even with newer Oils, the Design of the Engine requires 16:1 for Survival

 

[Mc Tool]

Yeah I googled it and was told that it has non caged needle rollers but tbh I was expecting to find bushes and as you posted jimmbo, it looks like plain bearings, and I recall my Dads old seagull book saying it needed 16:1 as much for sealing as for lubrication ( ½ a pint to the gallon ). You'd think it would have to be swimming in oil to survive 70 years without rolling element bearings or pressure fed plain bearings

 

[jimmbo]

I recall the Seagull requiring a 10:1 mix

Yes more Oil can hide a Leaky Crankshaft Seal. I found a few by adding more Oil to the Gas, and the Motor had restored Power, though it can make a Mess of the Ignition System

I know the 1957 - 63 Big Twin Engines(35hp and 40hp), and the 1958-63 V4s were full Antifriction Bearings and could run on 50:1 using a TCW Oil even though they were 24:1 motors when released. In 1964, OMC changed the Ratio to 50:1 for the entire Line, and also increased the Warranty Period to 2 Full Years. Comparing the Parts Books of the 63 and 64 40hp, and 75hp, the Only differences, besides switching to a Hot Air Autochoke, from the Hot Water Autochoke, was the Pistons came with a Tin Plating, to make Break In Easier. All the Bearings, Crankshaft, Crankcase Seal Rings, were the same Parts #s

 

[racerone]

There is nothing " scientific " about changing from 24:1 and going to 50:1 in my opinion.-----If you are losing sales because the competition is at 50:1 the board room made the change.

 

[jimmbo]

In 63, I think Mercury was still running 20:1

 

[Crosbyman]

Oil is cheap compared to repairs... I always ran oldies pre-60s with 1L/25L on TCW3.