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  1. #1

    Default "I have a merc 115hp 4 stroke

    "I have a merc 115hp 4 stroke efi. It smokes when I start it up. Not alot, but a few puffs and then it runs fine. I've been told that having the motor trimmed in causes oil to seep past the rings and that its perfectly normal for a 4 stroke to smoke at startup. When I leave it tilted up a bit, no smoke. Any opinions? Do I have a problem or is Merc right in their explanation?"

  2. #2
    Join Date
    May 2007
    Inverary, Ontario, Canada - The Great White North Eh!

    Default "Tom, 4 stroke motors are stil

    "Tom, 4 stroke motors are still pretty much a "new invention" to most of us on here - so your questions may tend to go unanswered.

    I do have service manuals for 4 strokes and did have a read through the one pertaining to your motor.

    It appears to have a system much the same as a car - oil sump/pump which pumps the oil at about 27 psi up through the filter, into the journals and ultimately to the cylinders.

    Since the sump is below the powerhead, and fed to the pump via a pick-up it would lead me to question why oil would be in the the cylinders (and leak past the rings) when the motor isn't running, unless the motor was pretty close to being upside down (???)

    All I can compare your situation to is a normal vehicle - if it smokes when you start your car, that's usually the first sign of the rings starting to go.

    Perhaps though there is someone here who has experience with 4 stroke outboards and can add their opinion.

    The only other point I can pass along from the service manual is - if you are operating the motor in an area where the temperature is consistently above 40 degrees (F), then you should use 25W40 oil as opposed to 10W30."

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  3. #3

    Default "Thanks Graham. I got the exp

    "Thanks Graham. I got the explanation that oil might be seeping by the rings from a dealer I took it to, from another merc authorized mechanic at another dealer and also directly from merc. I'm just having a hard time buying the explanation. I was hoping that someone here would have some experience that they could share. I tend to question their explanation for the same reasons you have. The only thing I can think of is that the cylindars are horizantal and the lower cylindar does tilt downward towards the combustion chamber when it is trimmed in. Again...thanks for your thoughts."

  4. #4
    Join Date
    May 2007
    Inverary, Ontario, Canada - The Great White North Eh!

    Default "Tom, I would be interested if

    "Tom, I would be interested if you ever do get a "good" explanation. I work exclusively on 2 strokes but know full well that in say, 10 years, there will be alot of "old" 4 strokes out there that need to be looked at.

    These are still pretty new to most of us here and somewhat of a mystery in some of their issues and/or "quirks"...."

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  5. #5
    Join Date
    Oct 2007
    Winnsboro, Louisiana, Franklin

    Default "Tom, I would think that if t

    I would think that if those four strokes are built like an auto engine you may have some bad valve stem gaskets. Over a period of time, they will harden up and lose their elacticity and ability to seal, allowing oil that is on top of the stem to seep down into the cylinder. I would pull a compression test on it and if all the cylinders show to be close to each other and within mfg. specks I wouldn't be concerned about it."

  6. #6
    Join Date
    Sep 2007

    Default Any leftover oil that that is

    Any leftover oil that that is stuck to the cylinder wall's does find its way past the piston rings into the chamber if the motor is not sitting level. If you leave it tucked under it will run down hill. The cylinders are stacked up horizontaly. Dont tilt it any farther back than you need to either. This also scatters the oil. Leave the oil level half way up the safe zone. Don't top off.

    115's seem to be more susaptable to this than others.

  7. #7

    Default "Thanks Bandit. That is basic

    "Thanks Bandit. That is basically the explanation that I am getting. I've heard some boaters say it happens to them similar to my experience and others say it never happens(smokeing at startup) I've also been looking at my transom as compared to other boats. I think my transom is at a steeper angle and that may be a reason that I see the issue and others dont. I hate to be a worry wart, but its a relatively new motor and I just wanted to be sure."

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