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Old 09-10-2010
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Question Bybass Oil injection?

Please reply with your 2 cents! I am debating whether or not to bypass the oil injection system in my 40 and 70 yamaha. The 40's oil injection system went out on me, and the oil lvl sensor went out on the 70. So now I'm faced with the decision of whether or not to spend money to fix (and maintain), or just mix my 50:1 in the fuel. I have friends that bybass the injection systems on brand new motors to avoid catastrophy and I have others tell me they rely on the system......What should I do please take the time to weigh in with your reasoning.
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Old 09-11-2010
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Yamaha has an extremely good track record with their oil injection system, I prefer to keep the oil injection system on them.
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Old 09-11-2010
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hmmm ok...i appreciate it
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Old 09-14-2010
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Yamaha has a very reliable oil system...if it's maintained, which can be a PIA. I chose to disconnect mine and avoid any problems with a ceased powerhead. I does happen... just search the forum.
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Old 09-14-2010
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Fix it. The oil injection system work well on Yamaha outboards. The route of bypassing the injection system opens you up to other problems. You may think that just mixing oil in your gas is easy but it can have catastrophic results as well as normal running problems. Most oil injection problems are self inflicted. Using good quality oil and keeping out contaminants are key. Yes a sensor can go bad , but if the alarm system is operational you should not have a catastrophic failure. Just think, cheap gas will ruin your engine just as fast.

Your engine is a living, breathing machine and is what it eats. If you were to eat at McDonald every day morning noon and night , would you live long and healthy? No. So you try to good food. Same with your engines feed them quality gas and oil and they will live and perform well.
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Old 09-14-2010
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My 1999 Yamaha 90C is a premix motor and I love it, just one less thing to screw up! But I've owned a Yamaha 115 with oil injection on it and it always worked fine. I just prefer stuff to be as simple as possible so I can learn it, understand it and maybe work on it when necessary! My $.02 worth!
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Old 09-15-2010
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What other problems MRV? Before I disconnected I searched this forum for any problems with disconnecting the oil injection and got nothing. Search this forum for problems people are having with the oil injection and you better grab a cup of coffee and put on your reading glasses; you'll be at it for a while. I spend hours reading every page of posts on this forum and came to the conclusion that these 2-strokes blow up because of cooling problems or oiling problems. I eliminated 50% of that possibility. Again...good system but proper maintenance is seldom done. I have an 02 sensor and run Amsoil and ring free and have no problems, and I troll for hours. More importantly, I never have to worry about a problem with oiling. To each his own...
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Old 09-15-2010
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Default Oil Injection

I have two 1986 115 HP engines on my boat and have always run the oil injection system. The only items I have replaced in all these years is the oil control module and the pumps on both engines. The pumps were replaced due to check valves leaking but not because they failed. It is a very reliable system in my book.
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Old 09-15-2010
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All good info my fellow Yamaha owners. I have come to a desicion....I think....hell I dont know.... I might bybass one and fix the other. The sensor went bad on one and the pump went bad on the other...almost froze my engine up('98 40), but it was the second thing on my troubleshooting list to check out...AND i might add that the over heat sensor did not go off...the engine would just lock up if i opened it up. Ill just have to keep an extra gallon of oil onboard with my oil injected engine incase.....bah I'll bypass both of them...simpler in my eyes just to premix and know for sure your oiled up..by the way Good point about searching the threads for problems with pre mixing VS. problems with the injection system.

-Banjo:
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Old 09-16-2010
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There exsists a theory that premixing will cause the engine to run too lean. I'd like to read more references to that. I'm having a hard time buying into that because when cruising she's mixing at 50:1 with the auto oiler.
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Old 09-16-2010
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Right Tucker, and when shes idleing its like 100:1 to 200:1...so if anything your over oiling when she is not wide open.....right?

-banjo
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Old 09-17-2010
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The main problem is people not adding the correct amount of oil to the tank from time to time or forgetting it altogether or not getting it mixed up well, especially in the larger tanks.

The smaller ones can be shaken to mix.

The proper way on large tanks is to add the oil to a few gallons in a small tank, mix it up good,and then pour into main tank before filling the rest of the way up. If you pour oil directly into tank it tends to slip down to bottom of tank and not get mixed completely so some of the fuel will be lean on oil and some rich.

The oil injection system is a better way. All you have to do is do the preventative maintenance and use good clean oil.To each his own.
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Old 09-17-2010
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Correct Banjo, at idle you're at 50:1 instead of 100:1. My opinion is this is for emissions purposes only. Someone determined that a 2-cycle engine can live with that. However, there is a commercial charter guy on this forum that says he gets 5000 hrs out of an engine premixed and 3000 hrs from the same engine oil injected. That math was enough for me. This guy is a hard core Yamaha man, I believe he has 6 or 8 big blocks and declares these are the best made engines period. In addition there are some engine rebuilders that will not warrant a rebuilt engine unless the injection is disconnected.
Im sorry 99Yam but I have to disagree. The latest 2-cycle oil is designed to mix almost instantly. In fact, with the exception of the HPDI models, the oiler drops the oil in the VST where is is "mixed" with that gas before going into the injectors or carb; at least in theory. I find it hard to believe that when cooking along at about 4100 RPM you get a 50:1 "precision blend" of premixed fuel. But I have to agree, you have to do a bit of thinking when premixing. I don't have fuel mgt gauges so I go by the half a$$ fuel gages and a note pad and calculator. All of this is thrown out the window with the HPDI. That is a completely different animal and is claimed to be the best engine Yamaha has made. I'm not too familiar with it but guys who have them love them. Again, reading this forum the main problem guys have problems with is...you guessed it the auto oiler.
I stand by the conviction that says auto oilers were designed to make 2-cycles environmentally compliant. They do nothing for performance or engine longevity. This is my opinion and I welcome knowledgeble arguments that would help change my mind. I'm not a mechanic but because of forums like this we can learn from other's experiences and become grass roots experts. I have to agree with your last statement 99YAM. Do the preventative maintenace and you "should" be fine. If I can avoid another "system" to maintain and worry about, I'm going to do it. And the maintenance isn't all that easy. My oil tank was in a compartment accessed by a 10" X 10" hatch.
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Old 09-18-2010
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Angry

Well I can tell you all this. I have a 92 70 "Presicion Blend" I have been working on. Finally after solving several problems, the first was the oil lvl sensor.....the last being 'the timing was way off', I put the boat in the water and it ran like a clock! I was so excited! Once I get home I'm gonna put it on my other boat and get it ready for the duck season....and on my way back to the dock when I was dreaming of all of that ......waaaaaaaaaaaaaaaaauuuuuump!!!!!!! the engine temperarely froze up because the Oiler Went Out! I guess the PM wasn't done on either of the engines I have, because both of the oilers went out. Now I need to recheck compression and bypass the oiler and all that jazz. This is the exact reason I started this thread, but the oiler went out before I even put the dam thing on my boat. I guess I dont need anyones advice any more. Needless to say both of my previous outo oilers are now going to be pre mix. BTW I like the calculator idea at the gas pump....I usually just make sure I put a precalculated amount in the tank, but if you have a cell phone handy you have no problem figuring out excactly how much oil to blend with any amount of gas!...
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Old 09-19-2010
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How do you know the oil pump/system went out?

Usually lack of oil will get the bearings and crank before a piston and a lean fuel/air ratio will usually get a piston first.
Even the wrong timing will get a piston. You need to make sure what happened before blaming it on the oil system.

Did you clean the tanks,change the filters, retrieve the old seal and install a new one when you changed out the level switch,make sure no junk got into the pump,and then make sure the check valves were functioning properly?
These oil pumps are really reliable being gear driven off of the crankshaft as long as you keep the trash out of the system so they can get the oil to pump.
There are ways of testing the oil system to make sure it is flowing the proper amount of oil without running till it locks up. It is all in your Yamaha service manual.

But that is all besides the point now, what you need to do at this point is find out what has happened to the motor and then go from there.
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