Saving Old Seagulls

is ep90 the same as sae90 for gears on my outboard engines

Andyboy

They are different.

EP90 is sae90 fortified with the addition of 'extreme pressure' (EP) additives specifically for gear type applications. Hypoid drives & final reductions the like. I seem to remember it having extra molydneum disulfide.

Your workshop test for unlabelled containers is to give it a sniff. EP oils smell quite different. EP90 is quite harsh. SAE90 is fairly pleasant. Difficult to describe smells.

Either way, water ingress is a big issue on seagull gearboxes. My experience has seen at least 10x more gearboxes ruined by water, as, opposed to wear.

I like to use oil specifically able to handle water. And change it really often

Rex

Rex, I agree with you about the most gearbox damage being the result of corrosion. Much of that is because of the use of grease, which of course won't flow and won't mix with water to form the emulsion they need. As gearboxes are stored, those portions that don't have grease on them - where tooth to tooth contact has removed it - are exposed either to water or air. Corrosion is the result.

Either type of 90 grade oil is fine (if that's the recommended grade for your gearbox) but they are actually different. I hadn't noticed the smell!

I believe British Seagull sold both EP and ordinary; they certainly did in the 140 grade.

andyboy wrote:is ep90 the same as sae90 for gears on my outboard engines

The figure 90 refers to the viscosity. EP means that the oil contains "extreme pressure" additives essential for ceratin uses. However the situation is more complex than being simply "EP" or not so the tendency now is to refer to the API specification system rather than to label an oil "EP"

A reasonably good explanation of the API specifications for gear oils, and more, can be found on This page and also HERE

For an outboard engine gear box you would well be advised to use an outboard engine gear oil which, they tell us, contains emulsifiers and corrosion inhibitors in excess of the requirements of the API specifications to guard against the effects of water ingress.