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Results 1 to 18 of 18
  1. #1

    Default 1992 Mariner 15 HP outboard trouble

    Hi guys, I've been bringing an older outboard back to life, but I've run into some trouble. After rebuilding the carb, the engine starts very easily with one pull, and idles okay. I did a compression test, and while it came back at 95 and 100 psi for the cylinders, it did seem that on #1 there were a couple of cycles where the pressure did not increase. The manual says this might be a sticking reed valve or incorrectly set timing. The reeds look fine, but I ordered new ones anyway. The manual says that to set the timing, I first need to run the engine up at full throttle and check the spark advance. The problem is that the motor vibrates so much and smokes so badly when above 1/2 throttle (it is just billowing smoke) that I'm afraid to rev it up any more. I know the carb is good and the gas is exactly 50:1 with fresh gas. How do I set the timing? Any other ideas?

  2. #2
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,293

    Default Re: 1992 Mariner 15 HP outboard trouble

    Are you sure it is firing on both cylinders? Disconnect one at a time to see if it still runs.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  3. #3

    Default Re: 1992 Mariner 15 HP outboard trouble

    Yes, I tried that and it runs on each one...

  4. #4
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,621

    Default Re: 1992 Mariner 15 HP outboard trouble

    Sorry, the reed valves have to do with compression in the crankcase and NOT in the cylinder.----Does the manual fuel pump on the hose go hard after the caruretor is filled ?

  5. #5

    Default Re: 1992 Mariner 15 HP outboard trouble

    Yes, the old line was bad so I installed a brand new one. Also a new tank source and fuel filter. I do have about 1oz of Seafoam per gal gas, and I'm thinking of making just straight 50:1 to see if there is a difference.

  6. #6
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,293

    Default Re: 1992 Mariner 15 HP outboard trouble

    1oz of Seafoam per gal gas won't make it smoke heavily.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  7. #7
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,433

    Default Re: 1992 Mariner 15 HP outboard trouble

    Is there an oily film on the powerhead itself - in particular, just put your finger up under the flywheel and give the top of the powerhead a wipe. The 6/8/9.9/15 horse powerheads are notorious for blowing two things - the upper main crank seal and the intake gasket (the one on the starboard side back near the plugs, not the one behind the carb).

    Both conditions will make it seem like a 1.5 cylinder model which often leads (mistakenly) to carb repairs.

    So check for the oil sheen (almost like the motor was "fogged") and if it's not present I would check out the intake gasket..
    Graham

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

  8. #8

    Default Re: 1992 Mariner 15 HP outboard trouble

    The plot thickens. I was able to remove the intake and exhaust covers yesterday. Here is what I found inside:Click image for larger version. 

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    There was a small black patch inside the intake cover and also on part of the intake itself. I am assuming that this is carbon buildup? The piston side walls and rings look clean, but the heads are also covered with this black sludge making me think it is all over the inside of the upper cylinder walls. I tried wiping it off the tops of the pistons with a Qtip, but it is more burnt on there. The exhaust cover was simply caked with this black sludge. It wipes right off with a paper towel, but you can see inside that the tops of the pistons are covered with it sort of burned on. I am assuming that this is what is causing all of the smoke when the engine runs. Kind of like when you have something on the bottom of your oven and you turn it back on - it smokes like crazy. Is this right? Is a complete tear down in order, or is there another way to clean this out?

  9. #9
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,293

    Default Re: 1992 Mariner 15 HP outboard trouble

    What oil has been used in the gas...4 cycle motor oil? Carbon buildup on the pistons can be removed w/a Seafoam treatment. Is there a thermostat in this engine?
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  10. #10

    Default Re: 1992 Mariner 15 HP outboard trouble

    I bought this used about 3 weeks ago. I do not know the history of the outboard before that, other than to say that the outside of the outboard and tank were caked in black grease. I had heard it was used as a dinghy motor by a lobsterman. The gas now has 2-cycle quicksilver 2-stroke outboard oil at 50:1. Believe it or not, I did perform a Seafoam treatment. This is after the first attempt. Maybe it didn't get in there? Yes there is a thermostat. I pulled it yesterday and it was gunked up (see pic) but I cleaned it up and tested it in a cup of hot water. Still works fine. So i put it back in.Click image for larger version. 

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  11. #11
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
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    Default Re: 1992 Mariner 15 HP outboard trouble

    but I cleaned it up and tested it in a cup of hot water. Still works fine.
    At what temp did it open? The engine needs to be at operating temp. for good combustion. I would replace it due to age and condition...unreliable. Repeat the seafoam treatment but let it soak overnight not 15 mins.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  12. #12

    Default Re: 1992 Mariner 15 HP outboard trouble

    Okay, that sounds like good advice. The thermostat is only $20. Does the engine need to be warm when I Seafoam it? The bottle recommends it, but if I leave it overnight then it will cool off anyway. Should I tip it on it's side and just pour it into the cylinder? Anything better than Seafoam? Thanks.

  13. #13
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,433

    Default Re: 1992 Mariner 15 HP outboard trouble

    Your intake/exhaust looked fine. Agree with Guy, change the thermostat. These did NOT ship from factory with a thermostat, but they are essential for a smooth idle and better cold starts - so yes, chuck the 20 bucks.

    Also agree - either too much oil or a "non" TCW3 oil has been/was used. TCW3 (water cooled outboard oil) burns up at the lower temp of a water cooled engine. Lawnmower/chainsaw 2 stroke oil, while often cheaper in prices, needs a considerably higher engine temp (like on an air cooled engine) to burn up without leaving a bunch of sludge behind.

    Also noted some build-up/slime on your thermostat. Since we are just talking about a 15 horse here this is what I would do to ensure all the water channels are cleaned out nicely.

    Put the thermostat back in (or at least replace the cover) - remove the lower unit and turn the motor upside down. Then make up a solution of 50% white vinegar and 50% tap water and pour it down the water tube until it starts leaking from the exhaust plate (this with the motor still upside down). Leave it like that for about 24 hours. The acid in the vinegar will eat all the lime, rust, calcium, salt etc that is in the engines water channels without hurting anything else. You can buy a commercial product that does the same, but with vinegar barely over a buck a gallon, you won't find anything cheaper....

    And "anything better than Seafoam" - for "fast fast relief" I prefer a product from Merc called "Powertune". Comes in a spray can (runs about 10 bucks) - it's like Seafoam on steroids. It cleans out everything but the metal (a substance that resembles McDonald's chocolate milkshake spilled on a sidewalk comes from the exhaust when using Powertune - I usually keep going until it (drips) clear - 1 can usually lasts for a half dozen treatments (or more) and is my product of choice when bringing motors out of winter storage that have been "fogged")
    Graham

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

  14. #14
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,293

    Default Re: 1992 Mariner 15 HP outboard trouble

    a product from Merc called "Powertune
    I'll have to give it a try.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  15. #15
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    12,421

    Default Re: 1992 Mariner 15 HP outboard trouble

    Compression is too low. Hone and re-ring.

    Jeff

  16. #16

    Default Re: 1992 Mariner 15 HP outboard trouble

    Hi Jeff, I'm really just a weekend warrior, but I've got the engine block off, crankcase separated, and pistons out. When you say hone, do you mean cylinders or pistons? Take it to a local machine shop?

  17. #17
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
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    8,433

    Default Re: 1992 Mariner 15 HP outboard trouble

    I don't know Jeff - I personally would be ok with a 95/100 compression on a 15 horse.

    115 to 125 would be a "new" engine so it's down by maybe 20%'ish, but the balance is fine (and don't know the calibration of the pressure gauge) -

    However, now that you have her split, Jeff was referring to honing the cylinders. These "jugheads" (split block/headless motors) can be honed to (clean them up) or even be bored out to .015 over. Personally, I would take it into a machine shop and have them do it - they know what they are doing and even if it needs to be bored you are out less than 100 bucks.

    If it does need to be bored you are looking at about 200 bucks a hole for a replacement piston/ring set (oversize piston goes for about 150, rings about 50 bucks a set) - but will say that in many many years of working on jugheads I have never come accross one that needed to be bored simply due to normal wear and tear (and even some significant abuse) - they just don't break.

    However, if you get it honed (or do it yourself), you might really want to consider dropping 100 bucks on a new set of rings for her - you will never do them again (and the motor can well last you another 30 years - I'm serious about the 30 year part, these are awesome motors - I personally own 3, a pair of 9.9's and a 15, with the "youngest" being 23 years old - all have well in excess of 1000 hours use (actual run time - and the 15 probably has at least 2000 hours)
    Graham

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

  18. #18

    Default Re: 1992 Mariner 15 HP outboard trouble

    Thanks very much Graham. The cylinder block is at the machine shop. I bought new rings too, so hopefully when I get it all back and put it together, it will be like new.

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