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Old 18 September 2021, 11:44   #1
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100:1 or 50:1?

Riddle me this: a sticker on the engine says 100:1 2-stroke mix, but the manual says 50:1.

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Old 18 September 2021, 11:59   #2
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It's a Tohatsu underneath. My Tohatsu version is 50:1

IMVHO, if you intend to use it at lower revs then 100:1 is fine. IIWY I would try it at 50:1 and if you're not fouling plugs then stick with that.

Obviously, the previous owner was using 100:1
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Old 18 September 2021, 12:08   #3
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There is something about 100:1 that just doesn’t feel right when adding the oil to a gallon of fuel.
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Old 18 September 2021, 14:23   #4
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That’s similar to my Mercury 3.3 which I run on 50-1 too much oil chokes the plug not enough might seize the engine
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Old 18 September 2021, 15:13   #5
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Both my motors are badged as 100. But I run em at 50.
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Old 18 September 2021, 17:26   #6
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The manual for my Suzuki DT4 says 100:1 unless used in South Africa or commercially in which case use 50:1.
I use 50:1 & haven't had any problems.
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Old 19 September 2021, 09:43   #7
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Thanks all. 50 seems to be the safe side, so I'll go with that.
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Old 19 September 2021, 10:45   #8
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If using hard then 50. If you find the plug is getting mucky then it's just telling you that for the way you use it 100 is fine.

And damage caused by excess oil will be temporary. Any damages caused by insufficient oil will be permanent.
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Old 19 September 2021, 12:34   #9
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Just carry spare plugs.
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Old 19 September 2021, 12:46   #10
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I used to have a 15hp Yamaha that I used on my Orkney Longliner, it was a 100:1 but not on my watch so I used to run it at 50:1, when trolling for a half hour or more it used to start coughing and spluttering as the plugs fouled up. A quick blast at full revs would clear it for another half hour.
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Old 19 September 2021, 14:37   #11
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Quote:
Originally Posted by A1an View Post
I used to have a 15hp Yamaha that I used on my Orkney Longliner, it was a 100:1 but not on my watch so I used to run it at 50:1, when trolling for a half hour or more it used to start coughing and spluttering as the plugs fouled up. A quick blast at full revs would clear it for another half hour.
Yup. I've a 15 Mariner of the Yamaha ilk. I bought it this season and it took me a while to work out the oil mix as everything on the web said 50. I eventually resorted to asking my 86 year old father who recalled the reason he switched to Yamaha in the mid 80s was that all their sub 40 engines ran on 100 so he didn't need different mixes.

My 15 runs on 100 and gets dirty on 50. All I do now is put a little extra in the tank if the engine is going to run flat out for long periods that day, so in reality I'm probably running 80:1 most of the time which doesn't foul but makes me feel I'm looking after an old engine.
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Old 19 September 2021, 15:08   #12
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I always ran my 100:1 engines at 75:1 or 80:1. Now my OB is a 50:1 there's no dilemma.
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Old 19 September 2021, 19:34   #13
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I had a Yamaha 9.9 that would smoke if I gave it anything more than 100 to 1 . I just didn't like the engine so I got rid of it . I'll stick with my Johnson Evinrudes that use 50 to 1 .
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Old 20 September 2021, 07:22   #14
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I find the mercury synthetic oil doesn't smoke hardly at all and reasonably priced. I run 50:1 on the 9.9.
Run it occasionally at high revs to keep the plugs clean. Check the plugs once and a while and go from there.
Not sure what you can get over there for synthetic but I have been using it for quite a long time and plugs are always pretty decent.
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