Yamaha 5HP - Pre 1973 2-Stroke mix

[markpoint]

Anyone know if a 1970 - 1973 Yam 5HP air cooled outboard reqires 50:1 or 100:1 - I read from Yamaha I should use unleaded from 1970 onwards ! - also if anyone has a 5hp Yamaha of same vintage is it possible to by-pass the integral fuel tank as its a bit rusty and the OutB has an external fuel line connector but it's has a rather large diameter, around 10mm.

I have cleaned the tank with phosphoric acid 3-4 times and flushed,WD-40ed and dried on numerous occasons but don't really want to take a chance with an Aux/backup engine.

Can't afford a new unit at the moment , so any Yamaha advice welcome. I have just had a 40HP Yamaha OB serviced but again, any advice re. maintanace welcome. I have flush muffs, books by various "experts" but I find practical experience the best teacher.

Thanks

 

[chippie]

I dont think you will go wrong with 50:1.
I recall seeing on a boating forum somewhere that the 100:1 mixes were to get the outboards through an emission testing program and many yamaha mechanics recommended their customers revert to 50:1.

If you can source an appropriate connector you can fit it to the hose of a remote tank without too many problems.

 

[graham]

I had an old Yamaha air cooled 5hp ran on 50 to 1 .get yourself some ear plugs if its the same as my old one. /forums/images/graemlins/grin.gif

i was told that even though its air cooled not to run it out of the water,something to do with the exhaust .