1986 40 hp mariner.

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If you change your mix pay close attention to your spark plug.

On side note I've got a lot of spare parts around the garage for this motor. Lmk if you need anything.
 
If it calls for 50:1, I would run it 50:1.

Running a motor lean on lubrication is never a wise idea.
 
Thanks and I will def let you know if I need any parts, I will check to see what the mix is .... It's just a little hard to find because it's a merc. / mariner / yamaha / Mitsubishi!
 
40:1 is more oil than 50:1.

Ask your source how adding more oil is going to make more power? If anything, the power would be slightly less-although probably not noticeable by anything but a sensitive dyno. Why you ask? The motor has carbs. The carbs have jets. The jet is what meters the amount of fluid that passes through. The oil is mixed with the fuel. The addition of oil changes the way that the fuel mixture can pass through that same jet. More oil usually means less fuel can pass through because the oil is displacing some of the fuel. So with more oil, you have good lubrication but the engine then has a tendancy to run leaner, which is why I assume sixgun suggested to watch your spark plugs closely.

Have seen it before too. Some Yamahas are designed to run at 100:1 which is roughly 1.3 ounces per gallon of fuel. Tons of people out there have been runnng their old JohnnyRudes and Mercs at 50:1 for 4011 years and they think that 100:1 is too lean, so they run their Yamaha at 50:1. Next thing you know, they're low on compression...pull the head, find a burned piston due to lean running. Even though there's twice as much oil, there's quite a bit less fuel. Leads to detonation and lean burn, which on a 2 stroke WILL kill it, and quickly. Talk about tee'd off customers. They can't understand how more oil can destroy an engine. And being that those types are typically a little hard headed, I can't change their mind by explaining it. Normally they'll go away cussing the outboard they bought saying that they're junk, and that they're going to go plant flowers in it and buy another brand. When the sticker says 100:1, or 50:1, or 25:1 or whatever it says, stick to it unless you know what you're doing. Either that or prepare to flag down another boater...and make sure you've got a rope :)
 

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