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Old 27 April 2007, 16:18   #1
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Correct Oil Ratio for Yamaha 5HP 2stroke

I am bidding on a 10 year old Yamaha 5HP on ebay. The guy says it runs on 100:1 oiletrol mix. Is this correct, it sounds like too little to me?

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Old 27 April 2007, 16:21   #2
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my 9.9 runs at 1-100 but it doesnt rev high for long periods. if im going to use it at wot i use 70-1
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Old 27 April 2007, 16:48   #3
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The handbook says 100:1 but I usually run premix of 50:1/70:1
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Old 27 April 2007, 17:49   #4
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Apparently the older blue coloured engines should run at 50.1 wheras the later grey coloured ones are 100.1

I got this from a Yamaha dealer.

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Old 27 April 2007, 19:51   #5
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The reason they say 100:1 is for the sake of environmental laws - for the sake of the engine 50:1 is much better!!!
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Old 27 April 2007, 20:09   #6
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Apparently it does no harm running at 50:1.Apparently when running at 100:1 they run a bit hotter.
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Old 30 April 2007, 16:19   #7
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Had a 4hp BLUE Yamaha in the late 80s / early 1990s.
And a 20hp BLUE Yamaha 20 in about 1990.

Both had 100:1 marked on them. Used to put a bit extra in for luck though - most other outboards of that time were on 50:1.

The 20 used to oil up a bit on 50:1 at river speeds.
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Old 30 April 2007, 19:30   #8
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Guys,

It seems that the best bet would be to run it a 75:1 then ;-)
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Old 01 May 2007, 00:23   #9
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Quote:
Originally Posted by Chris1573 View Post
Guys,

It seems that the best bet would be to run it a 75:1 then ;-)
safe bet
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