50:1 100:1? Finding the right mix for your outboard.
Mercury Outboard Service Manual 1965-1989 2-40 HP; MERCURY DOWNLOAD 1965 1989 Service Manual 90 to 300 HP Outboard; MERCURY/MARINER DOWNLOAD 1965 1989 Service Manual 45 to 115 HP Outboard; MERCURY DOWNLOAD 2001 2002 Service Manual 115 HP 115HP EFI 4 Stroke; MERCURY DOWNLOAD 1997 1998 Service Manual 200/225 Optimax DFI 4 Stroke; Mercury Mariner. This Mercury 40 HP 2-Stroke outboard service manual is the same service manual used by professional marine technicians. If we can provide additional assistance of any kind please feel free to contact us and tell us what you need. We appreciate your business!
Why mix Fuel & Oil anyway?
Any outboard described as a 'two stroke' engine is an internal combustion engine than burins injected fuel through a reduced power cyle of just ignition and exaust (more info about the difference between two stroke and four stroke engines here. ) Due to this design it is necessary to provide the engine with lubrication (the oil) actually within the injected fuel (the petrol or gas). The relative proportions of these two components is called the 'fuel mix ratio'.
Getting the mix right
Every engine will have it's own fuel mix ratio, often mandated by power, intended use and age of the outboard and manufacters state this required mix ration and any tolerance (if there is any!) in the owners manual. Not running the right mix can cause poor starting, performance degradation, increase wear and tear and excessive smoke from the exhaust.
If however you don't have the original owners manual then you'll need to determine the right mix prior to use. Manufacturers often print the fuel mix ration on the inside or outside of the cowling, the fuel filler cap or sometimes embossed onto the fuel tank itself.
Mercury 40 Hp 4 Stroke For Sale
If all else fails a quick internet search of your outboard make, model and age will quickly reveal the required ratio. If you're absolutely stuck we recommend a mix of 50:1 for outboards older than 1980 and 100:1 for outboards manufactured since 1980. That is 50 parts fuel to 1 part oil and 100 parts fuel to 1 part oil respectively.
Mixing the Fuel
Once you've landed on the ratio you need actually do the mixing.
Always store, handle and mix outboard engine fuel in a well ventilated space, ideally outdoors and away from any source of ignition of chance of contamination, i.e. not on the ground of some dusty car park!
Prepare you fuel, oil on a bench or other suitable surface and have a clean rag and medium sized funnel handy. Aim to add the oil to the fuel rather than the other way around so have a suitable rounded number volume of fuel ready in a container (Starting with 5 Litres of petrol in a tank is ideal) and then added you two-stroke oil through the funnel mixing thoroughly.
2003 Mercury 40 Hp 2 Stroke Manual
Once you've finished mixing clean-up an spilt fuel or oil and make sure to commit to memory or note down which fuel tank has the mixed fuel ready to go.
Mercury 2 Stroke 40 Hp Manual Diagram
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