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Discussion Starter #1
I see a lot of post on various sites about outboards. Many people think premix is better (very old school). The following is from a Yamaha site & it may help someone decide about premix yes or no.

Precision Blend
Theory of Operation
In the past, all two-stroke outboard motors
required the oil and gas to be mixed in the
gas tank. This was the only way to lubricate
the engine.
This premix system, while simple, has several
drawbacks. The boat owner has to
remember to mix the oil and gas – which
can be a complicated and messy proposition.
The proper ratio is also important. If
the owner mixes the wrong ratio or forgets
the oil entirely and runs straight gas, the
engine could be damaged.
Even when the oil is mixed at the recommended
ratio, that ratio is only correct for
one narrow rpm band. An engine might
need as little as 200:1 at idle and as much
as 50:1 at wide-open throttle. The premix
ratio must be set to the richest mixture
needed to be safe. But that means that the
engine can get four times as much oil as
necessary at idle. This tends to foul plugs
and produce excessive smoke
 

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I've never had a problem premixing. If you forget to put oil in your gas then you probably shouldn't own an outboard. I have however had a problem with an outboard that you didn't have to premix. One of the injectors went bad and the motor burned up real quick. After talking with a good friend who runs the maintenance department at a large marine store back home he suggested to mix only and dont rely on the engine to mix. Just something else to go wrong. He said they have more problems out of engines that mix it for you rather than just mixing your own. Just my opinion but il always mix my own in a 2 stroke.
 

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Lots of theories on this. It really boils down to what type of two stroke. Older Johnson/Evinrudes, you had probably better be mixing your oil in gas. They had a long track record of VRO (oil pump) failures causing motor failures. The alarms would not sound fast enough when it would get hot before a piston was burned. I used to just carry and extra set of plugs (real cheap on those motors) in case I was a little oil heavy and may foul plugs. Basically, premixing with these motors you have eliminated the primary cause of engine failure (no oil) and as long as it keeps getting water to cool, they will run forever - they may just be a little smokey.

For older Yamaha's with the Precision Blend technology (and still carbureted), those set-ups were known to be more reliable. I had one of these that I did not pre-mix even when it was older.

Now for the newer Direct Injection 2 stroke motors, you cannot pre-mix. Well you can but you will likely cause problems. These are all Fuel Injected motors that require a very specific oil feed based on operating conditions. They also require a specific type of 2 stroke oil (low ash). These would be you Mercury OptiMax's, Evinrude ETEC's, and Yamaha VMAX's. All of these motors, especially the Optis, are very particular about fuel quality, oil blend, etc.
 

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If you premix, best money you can spend http://www.amazon.com/Shoreline-Mar...1433873348&sr=8-2&keywords=2+cycle+mix+bottle

I fill my gas, pour the oil to the right mark, pour in the take, Go fishing. Repeat Often!

I think Rebelles is right on, there is a big difference between new high tech 2 stoke motors, that are digitally controls and use tech similar to fuel injection. Version the old 2 strokes motors that had oil injection as a marketing ploy more than anything. Way to may stories of motors burned up for me to use oil injection on one of those older motors.
 

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Lots of theories on this. It really boils down to what type of two stroke. Older Johnson/Evinrudes, you had probably better be mixing your oil in gas. They had a long track record of VRO (oil pump) failures causing motor failures. The alarms would not sound fast enough when it would get hot before a piston was burned. I used to just carry and extra set of plugs (real cheap on those motors) in case I was a little oil heavy and may foul plugs. Basically, premixing with these motors you have eliminated the primary cause of engine failure (no oil) and as long as it keeps getting water to cool, they will run forever - they may just be a little smokey.

For older Yamaha's with the Precision Blend technology (and still carbureted), those set-ups were known to be more reliable. I had one of these that I did not pre-mix even when it was older.

Now for the newer Direct Injection 2 stroke motors, you cannot pre-mix. Well you can but you will likely cause problems. These are all Fuel Injected motors that require a very specific oil feed based on operating conditions. They also require a specific type of 2 stroke oil (low ash). These would be you Mercury OptiMax's, Evinrude ETEC's, and Yamaha VMAX's. All of these motors, especially the Optis, are very particular about fuel quality, oil blend, etc.
+100000^^^^^
And it is also very common to burn pistons with pre-mix gas..if you have a carburetor malfunction/ gas flow interruption to one or more cylinders... ..no gas = no oil...
 

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+100000^^^^^
And it is also very common to burn pistons with pre-mix gas..if you have a carburetor malfunction/ gas flow interruption to one or more cylinders... ..no gas = no oil...
I unfortunately know this to be a fact. The bottom carb on my motor was gunked up to the point of not giving the bottom cylinder any gas or oil and when I pulled the head off the bottom piston look like it was wrapped in aluminum foil it was so shiny from getting hot. The moral of the story when pre mixing is if you notice any loss in power or engine miss don't run the motor until you find out what it is because if it is a carburetor issue it could turn into a piston/ring and more issue.
 

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My engine is Yamaha HPDI and cannot be pre-mixed. The engine is designed to pump oil from reservoir to Pistons, crankcase etc. The fuel is also directly injected onto pistons individually. If I pre mixed I would not receive any oil to crankcase, only pistons. I used to carry a bottle with me just in case oil injection had problems I could mix oil directly into gas tank but it will not work. Older engines pulled gas and oil through carburetors. So before you bypass oil injection make sure you will still be getting oil everywhere needed
 

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I have a 200 Hp 2 stroke Yamaha OX 66 Saltwater series.I bought the boat and motor new in 2000.The dealer told me to fill the oil tank with oil and to also add a 50 to 1 premix to the gas for the first 10 hrs of run time.Long story short,after 10 hours I relied only on the oil injection.Its 15 years old now and run's like a new one.It has a built in system were if it runs hot or dosn't get enough oil the computor shuts it down to 2000 RPM's and the alarm goes off. I had a bad temprature sensor several years ago and above 4500 RPM's it would shut it back to 2000 RPM'S.After I replaced that, all is well again.I'm sold on Yamaha's.My motor may blow up tommorow ,but I have gotten my money's worth.This my thoughts on that.[smile]
 

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I know two people who've ruined engines because they didn't realize the injector quit working. Best solution -- buy a four stroke!! Loved my Suzuki 90hp that I had.
 

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If you premix, best money you can spend http://www.amazon.com/Shoreline-Mar...1433873348&sr=8-2&keywords=2+cycle+mix+bottle

I fill my gas, pour the oil to the right mark, pour in the take, Go fishing. Repeat Often!

I think Rebelles is right on, there is a big difference between new high tech 2 stoke motors, that are digitally controls and use tech similar to fuel injection. Version the old 2 strokes motors that had oil injection as a marketing ploy more than anything. Way to may stories of motors burned up for me to use oil injection on one of those older motors.
I have used that bottle for a few years now. Excellent tool.
There is a certain confidence in pre mixing.
96 Yamaha C75TLRU.
 

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Discussion Starter #11
Rebelles, on the Vmax 2 stroke it does not take a special oil. Just 2 stroke oil. If using Yamaha oil they only make 1 oil for a 2 stroke. No low ash oil. I do not know about 4 stroke. This is not my opinion but from the dealer 7 Seas here in Biloxi.I have a 2008 Vmax 150 on my boat..
 

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Rebelles, on the Vmax 2 stroke it does not take a special oil. Just 2 stroke oil. If using Yamaha oil they only make 1 oil for a 2 stroke. No low ash oil. I do not know about 4 stroke. This is not my opinion but from the dealer 7 Seas here in Biloxi.I have a 2008 Vmax 150 on my boat..
Sorry, I was referring to the newer VMAX's which are HPDI type motors(Direct Injection) and should have said HPDI in general. As noted earlier, the Direct Injection type 2 strokes require a different type of 2 stroke oil. There are multiple grades. OptiMax's and Etec for sure do, and I am pretty sure it is recommended for HPDI's also. Mercury and Evinrude make 3 different levels of oil for the various 2 stroke motors (ie. older generation carbureted motors up to newer version HPDI motors). The higher grades of these oil can be run in the older, carbureted 2 stroke motors, but the reverse is not true. Of course, these oils are a lot more expensive than the regular oil you run in the older 2 stroke motors that aren't DI motors. I have Yamaha 4 strokes on my bigger boat, so I am not sure about their 2 stroke oils. It is possible Yamaha only sells 2 stroke oil compatible with all types of 2 strokes. I have an Opti on my bay boat and have to buy the semi-synthetic low ash two stroke Mercury oil for it.

4 stroke motors don't mix any oil with the gas. The only oil they use is engine motor oil like a car motor.
 

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Follow-up - I looked up Yamaha's website to look at their YamahaLube. It is a semi-synthetic blend made for Direct Injection motors. So it can be run in all types of 2 strokes. But if you a running an older, carb'd 2 stroke, this oil isn't necessary and probably isn't worth the $11/quart price (which is in line with the comparable semi-synthetic DI oils from Mercury and Evinrude). It's not going to hurt those old motors, but I remember my old Evinrude's would run on any 2 stroke oil you could find.
 

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IT IS PROVEN. Pre mix its 100% better than having engine do it itself.. safer and less expensive on repairs... all you have to do is remember to add oil to gas...cant put diesel on a gas car so can go wrong on something as simple as adding oil to your babe....
 

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IT IS PROVEN. Pre mix its 100% better than having engine do it itself.. safer and less expensive on repairs... all you have to do is remember to add oil to gas...cant put diesel on a gas car so can go wrong on something as simple as adding oil to your babe....
What an odd first post!
 

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I rather change plugs out 2x a year verses burning my engine up not getting enough oil. I premix my old Johnson Faststrike.
 

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Had a Johnson 25 horse. It had a mixing tank for the oil. Had several friends tell me to plug it and mix my oil and gas. I didn’t. I seized it up. I bought a 4 stroke.
 

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main reason I bought a 4 stroke is I DO NOT trust those pump systems. I know you can say the oil pump can quit on a 4 stroke too, but that's not as likely.
 

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Here's my experience with oil injection. In 1984 I bought a new 21' HydraSport CC with a 150 Mercury Black Max with oil injection. I ran that motor for 21 years till Hurricane Katrina took it out. I had zero trouble with the oil injection. I'm now running a 2004 225 Optimax on my Triton 240 LTS. I bought this boat used with 38 hours on it in 2006. I've had zero trouble with the oil injection on it. Oil injection has never given me any issues, but it is a thing of the past.
 
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