Tony_reve Posted November 14, 2016 Share Posted November 14, 2016 Hey guys I have a 70hp early 90s model 2 stroke motor, every time I start the engine is blows a lot of smoke, I run a 25:1 oil to petrol mix. Is that the correct mixture ? can anybody give me a heads up Link to comment Share on other sites More sharing options...
Guest 4myson Posted November 14, 2016 Share Posted November 14, 2016 First of all what Outboard are you running ??? Most outboards run an oil tank That self mixes the correct ratio & if your adding in extra oil to the fuel this will cause it to blow smoke , So unless the oil tank has been disconnected there is no need to be adding oil to the fuel . And again need to know what outboard your running as some use a 50:1 mix . Link to comment Share on other sites More sharing options...
PaddyT Posted November 14, 2016 Share Posted November 14, 2016 Most outboards run 50:1 once they are run in so that would help- but using a synthetic oil will also reduce fumes but cost more for the oil- Link to comment Share on other sites More sharing options...
Tony_reve Posted November 14, 2016 Author Share Posted November 14, 2016 (edited) I am running a 90 model 70hp Yamaha and the oil tank has been disconnected so you think I should lower my oil mixture or higher it ? Edited November 14, 2016 by Tony_reve Link to comment Share on other sites More sharing options...
Guest Guest123456789 Posted November 14, 2016 Share Posted November 14, 2016 How old is the fuel you're using? What octane rating? What sort of oil are you using? When was your last service? I used 25:1 while running the outboard in and as per owners manual switched to 50:1 after the last service. I did notice significantly less fumes and smoke after doing so. Link to comment Share on other sites More sharing options...
Fab1 Posted November 14, 2016 Share Posted November 14, 2016 27 minutes ago, flatheadluke said: How old is the fuel you're using? What octane rating? What sort of oil are you using? When was your last service? I used 25:1 while running the outboard in and as per owners manual switched to 50:1 after the last service. I did notice significantly less fumes and smoke after doing so. Agree with this.Your 25:1 mix is very oil rich usually recommended for running In procedures and will smoke considerably.Given that your outboard is a 90's model I think that occurred a little while ago now.Give the 50:1 mix a try using fresh fuel and oil as stated above. My motor runs on a mix of 100:1 with very little smoke using Yamalube. When I ran it in using 25:1 I could see 10ft behind me,50:1 a lot better and 100:1 hardly any smoke. I don't run full throttle at 100:1 though and 99% of the time I'm at 75:1 for a good compromise. If your not doing it already give the tank a good shake prior to any trip if your running a portable tank. Good luck with it all. Link to comment Share on other sites More sharing options...
Tony_reve Posted November 14, 2016 Author Share Posted November 14, 2016 I run my fuel tanks to empty every time I go out so he fuel is always brand new and I only put unlended 98 in it with the outboard oil from caltex in it. My last service was about 40 hours ago. but next time I go out I will try a 50:1 ratio mix and see how I go. thanks for the advice guys. See yous in the water Link to comment Share on other sites More sharing options...
big Neil Posted November 14, 2016 Share Posted November 14, 2016 I run 100:1 in my 15hp Yamaha and never have any problems starting , running or idling (trolling). 25:1 seems extremely rich to me. Good luck. Link to comment Share on other sites More sharing options...
antonywardle Posted November 16, 2016 Share Posted November 16, 2016 I've also got a yamaha 15HP and its got written ont he side 100:1 25:1 is from the 60's ;-) (like me!) What model is it? Maybe we can find the correct answer for you Link to comment Share on other sites More sharing options...
NaClH2OK9 Posted November 16, 2016 Share Posted November 16, 2016 Mine used to smoke like a bugger on caltex oil. I switched to the manufacturer recommended (expensive evinrude) runs MUCH cleaner now. Link to comment Share on other sites More sharing options...
Guest Guest123456789 Posted November 16, 2016 Share Posted November 16, 2016 7 hours ago, NaClH2OK9 said: Mine used to smoke like a bugger on caltex oil. I switched to the manufacturer recommended (expensive evinrude) runs MUCH cleaner now. I can vouch for quicksilver oil. Big fishing and tackle stores stock it and it's a lot cheaper than the Suzuki brand outboard oil Link to comment Share on other sites More sharing options...
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