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  1. #1
    Seaman
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    Default adding oil to gas vs. auto injection

    I have a 1994 Tohatsu 60 HP that has and oil tank and it does the whole auto injection thing. However, I have read and heard and been told that many fellas don't trust that system because if it fails you burn up the motor. They state to mix your gas.

    Should I do this for insurance?
    Do I need to disconnect the oil injector system or can I mix and keep that system operational?
    Whether I keep it hooked up or only mix the gas... What ratio should I mix? 50:1? 25:1?

    I am new at all this so any help and comments would be helpful. Thanks in advance y'all.

  2. #2
    Supreme Mariner
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    Default Re: adding oil to gas vs. auto injection

    Whereas it is true that if the oil injection system fails, the motor burns up, it is also true that if you forget to add the oil to the gas, the motor burns up just the same. The question is who is more reliable, you or a mechanical system?

    I would start asking the Tohatsu gurus how reliable is the oil injection system and weigh their answers agains your personal reliability.

  3. #3
    Petty Officer 3rd Class
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    Default Re: adding oil to gas vs. auto injection

    Personally I prefer to premix, then I know if the motor is running it's getting oil.

    However as Chris points out, it still relies on someone remembering to mix in the 1st place!

    I have a simple routine, tote tank(s) out of boat, full up, then the tank does not go anywhere near the boat until it has oil added, once I've added oil, straight back into boat.

    So I know if it's not in the boat it hasn't got oil, and if it is, it has

    ...and I'll wager more motors have be burned from human failure than from mechanical

  4. #4
    Supreme Mariner
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    Default Re: adding oil to gas vs. auto injection

    The oil injection on my '98 Johnny 150HPV6 has been proven to be very reliable, and has low oil and no oil sensors. It is real convenient to use, versus mixing up 25gal of fuel each time I want to go fishing. The mix is always fresh as well.

  5. #5
    Supreme Mariner
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    Default Re: adding oil to gas vs. auto injection

    Disconnect the injection, disconnect the warning sensors. Doesn't make sense to me. We've rebuilt many more motors because someone forgot to add oil / didn't add enough than because of a TRUE injection system failure.

    Oil injection, don't leave the dock without it.

  6. #6
    Supreme Mariner Frank Acampora's Avatar
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    Default Re: adding oil to gas vs. auto injection

    How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

    I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.

  7. #7
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    Default Re: adding oil to gas vs. auto injection

    Quote Originally Posted by Frank Acampora View Post
    How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

    I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.
    Exactly!! Well put Frank!

  8. #8
    Admiral j_martin's Avatar
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    Default Re: adding oil to gas vs. auto injection

    Well, there are times when it's prudent to block off the oil system. On a V6 merc, the drive gear is nylon. If the engine is grossly overheated, that nylon gear is compromised. If you don't wreck the engine, it's a good idea to block off the oil pump at that time and pre-mix. You have to pull the powerhead and split it to replace that drive gear. Save the injection parts, as you will be overhauling it soon anyway, and that's a good time to refresh the nylon gear.

    The other time is if you mod the engine to turn extreme RPMS consistently. The Merc oil pump is not reliable above about 6500 rpm's.

    I once saw an old man cry on the landing. He had forgotten to add oil to the gas and fried a vintage (green) mercury 5 horse.

    Pay attention. Look into it if the power on self test (POST) tones are not heard when you turn on the key, and if the alarm goes off when running.

  9. #9
    Petty Officer 1st Class riptide09's Avatar
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    Default Re: adding oil to gas vs. auto injection

    I have never had a problem on my '03 Johnson. The oil injection system works as advertised and to me it is way more convenient than adding oil to the gas, especially when i don't know exactly how much gas it will take to fill the tank.

    If the oil injection systems were unreliable they would not continue to make them. Maybe when they first came out there were issues but that was 20+ something years ago.
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  10. #10
    Vice Admiral
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    Default Re: adding oil to gas vs. auto injection

    Have a buddy that does both. Pre-mixes at a 100:1 and still uses the oil injection.

  11. #11
    Lieutenant Commander
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    Default Re: adding oil to gas vs. auto injection

    Quote Originally Posted by tx1961whaler View Post
    Have a buddy that does both. Pre-mixes at a 100:1 and still uses the oil injection.
    Kind of like folks who ues synthetic oil in their car or truck and change it every 3000 miles. JUST TO BE SAFE.

    PEACE...of mind.

  12. #12
    Lieutenant Commander 109jb's Avatar
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    Default Re: adding oil to gas vs. auto injection

    Quote Originally Posted by Frank Acampora View Post
    How often does an oil pump on an automobile fail? Do we worry about that destroying our engine?

    I think that auto mix systems failing are an urban legend. Don't listen to the low oil warning or run without oil and you will ruin the engine, but that's not the pump's fault.
    This isn't even a good comparison. In our 4-stroke cars we have absolutely no choice because the lubrication system is not even connected to the fuel system. The oil and the fuel never mix. On a 2 stroke, the oil and gas mix, it is just a matter of whether a person or a piece of machinery is doing the mixing.

    Do 2-stroke oil injection systems fail. You bet they do, but they are for the most part very reliable. I ride snowmobiles and although I have never had an oil system failure I have a friend that had one fail and lost the engine.

    As was stated before it depends on the system. My father had a 60 hp Johnson with the VRO system. Not known for its stellar reliability. We disconnected it and ran premix in that engine. I now have a 115 Mariner and relatives have had many Mercury's and they have a reliable proven oil injection system. So, the system on my Mariner is still pumping oil into the engine.

    Can someone forget to premix?? Yes, I suppose, but I've premixed for 20+ years before the boat I have now and I never forgot because it was a given that you add oil every time you fill the gas tank.

    Can someone forget to add oil to the oil injection tank?? Yes. I have done this because the big oil tank lasts for many tanks of fuel. Has it ever gotten low enough to be a problem?? No, but if someone were to get complacent enough with checking the level then it could be a problem. I will tell you that when I got my boat the warning buzzer did not work. The buzzer itself was bad and all the sensors in the world don't mean nothing unless the sensor has a way to notify you.

    Like I said, to me it depends on the system whether I would unhook it. Some I would unhook, some I wouldn't.
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  13. #13
    Seaman
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    Default Re: adding oil to gas vs. auto injection

    Thank you all for your input and help. I have learned a lot.

    Does any one know the reliability of oil injection systems on Tohatsu motors?

  14. #14
    Lieutenant Commander
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    Default Re: adding oil to gas vs. auto injection

    Try posting your question on the Tohatsu board. Tohatsu Guru hangs out there and pretty much knows what there is to know about Tohatsu.

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