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Fuel Mixture Ratios

Year Manufactured/ Notes* Ratio 1 gal. gas 2 gal. gas 5 gal. gas
1931 to 1978 10:1 12.8 oz. oil 25.6 oz. oil 64 oz. oil
1978 on (older converted models*) 25:1 5.12 oz. oil 10.24 oz. oil 25.6 oz. oil
Roller bearing models ONLY** (25:1 recommended) 50:1 2.56 oz. oil 5.12 oz. oil 12.8 oz. oil

To calculate other fuel mix ratios, use CSGNetwork's online Marine Gas Oil Mixture Ratio Calculator.

Note: Outboards equipped with a Bing carburettor can use the 25:1 ratio.


All motors manufactured from January 1978 are designed to operate on a 25:1 petrol (gas)/oil ratio.

Motors manufactured since 1967*** can satisfactorily use this ratio, providing the following modifications are made:

We recommend Seagull Two-Stroke oil, however, if this is unobtainable, use a good quality two-stroke oil.

**The 50:1 ratio is NOT RECOMMENDED for any British Seagull Outboard. If you know or don't know the model of your outboard, use 25:1 or better.

***Motors built prior to 1967 should retain the 10:1 petrol oil ratio.