yamaha 2hp oil

[grafozz]

If , you had no EP 90 oil ... could ordinary engine oil , say 20 / 50 w , be used in the leg of a small outboard like the 2 stroke yamaha ? I am sure this would cause a problem in a car but would it do any harm in a little outboard ? I seem to recall race cars using lighter oil in diffs to reduce friction ...

 

[sailorman]

If , you had no EP 90 oil ... could ordinary engine oil , say 20 / 50 w , be used in the leg of a small outboard like the 2 stroke yamaha ? I am sure this would cause a problem in a car but would it do any harm in a little outboard ? I seem to recall race cars using lighter oil in diffs to reduce friction ...

unless its life or death NO

 

[gordmac]

From memory EP stands for extreme pressure, the type of gears that require it would, I suspect, not be well lubricated by oils not designed to deal with the loading. It may last a while, only way to find out is to try it and see! I wouldn't though.
In motorsport there is time to be had with less draggy oils, I would doubt that anyone would use unsuitable oils in places that need EP oils unless they have a lot of money to regularly rerplace bits assuming they would last a race.

 

[vyv_cox]

EP oils are specified in gearboxes that have hypoid gears. These have a 100% sliding action, which generates very little hydrodynamic lubrication, unlike plain gears which have a part rolling, part sliding mechanism. Where hydrodynamic lubrication is absent the oil needs to have a high level of boundary lubricant, = EP. Engine oils have a very small EP component, insufficient to lubricate hypoid gears.

I have no idea whether a 2 stroke Yamaha has hypoid gears or not, but the manufacturer has not specified EP oil for pleasure. Something in there needs EP and you would be unwise not to use it.

 

[VicS]

I have no idea whether a 2 stroke Yamaha has hypoid gears or not,

I am prepared to stick my neck on the line and say not. ( just plain old bevel gears) So strictly an EP oil should not be necessary.

Also consider than the SAE viscosity scale for gear oils is different to that for engine oils,

An SAE 20 engine oil has the same viscosity as a 75W or 80W gear oil.

On the basis that any oil is better than no oil in an emergency I would not be troubled by using a 20/50 engine oil

I would not want to run a big outboard all day at WOT with 20/50 in the gears but a 2 hp for a few short trips at moderate speed I really do not think will come to any harm.