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  1. #1
    RIN's Avatar
    RIN is offline Registered User
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    Default Found my old Mercury 7.5HP Outboard today

    In the back of the garage. Hasn't been used four 4 years. I am going to try and start it tomorrow. It would be ridiculous to expect it to start so has anyone got any suggestions for things I can try to coax it into life? It's a two stroke.
    Last edited by RIN; 17-03-10 at 22:38.

  2. #2
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    - Drop some 2-stroke oil down the spark plug holes, and make sure it turns over freely
    - New spark plugs
    - Fresh fuel
    - New impellor
    - WD40 sprayed around key electrical bits, check wires etc.

    See what happens!
    If it works, change the lower unit oil too.

  3. #3
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    an old merc 2 stroke... oh lovely.. what age?

    The first thing that I would do is take the spark plug out and put some penetrating oil in the cylinder and let it sit for a day. See if the motor will turn over, if it is stuck and will not turn put more penetrating oil in it. Don't try and force it or you may break a ring and you don't want that. Take a look at the carb, probably a quick strip & clean & rebuild wouldn't do any harm.. drain old mixed fuel out and replace, buy a new spark plug, and have a go.... if it runs great, if not put new points and condenser and you should be in good shape. Impeller will need renewing, do check the tell tail (assume you will be starting in a big bucket of water or the like?)

    tell us how you get on.


    edited bit;
    sorry, bit late but at least you are getting the same advice twice!!
    Last edited by Firefly625; 17-03-10 at 23:00.

  4. #4
    Tremlett 15's Avatar
    Tremlett 15 is offline Registered User
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    Quote Originally Posted by Firefly625 View Post
    an old merc 2 stroke... oh lovely.. what age?
    totally agree.......& yes what year ?

    7.5s built 1979 > 1985., 75s ( 7.5 ) built 1967 > 1987. which is urs ?

    you may not need new plugs, I am still running my 1976 Merc 500 on the original spark plugs...........and would go with the rest of the advise. Hope all go well & do let us know.

  5. #5
    RIN's Avatar
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    Not sure how old it is. We bought it second hand in 2001 as a "get you home" engine for our old bayliner and never did use it much. It has 7.5 on the side but no "s" It has two cylinders, no kill cord, I think you can track the age from the serial number so I'll have a go at that. It's currently mounted on a beam supported by two aluminium ladders and is sitting in our dustbin full of water in front of the pattio windows and SWMBO wants it moved. Now.

    Will report back tomorrow evening

  6. #6
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    4 years? That's a mere holiday for an outboard. Check it turns over OK with a gentle pull on the cord, change the fuel for a fresh batch & it should run fine.
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  7. #7
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    If it were mine I'd give it some fresh fuel and see if it starts. I have an old Yamaha 2 which sat in the engine room on my old boat unused for over 2 years. When I finally took it out it started 2nd pull, didn't even change the petrol. Now in my garage, been there 3 years, might give it a look today, expect the same result.

  8. #8
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    Quote Originally Posted by longjohnsilver View Post
    If it were mine I'd give it some fresh fuel and see if it starts. I have an old Yamaha 2 which sat in the engine room on my old boat unused for over 2 years. When I finally took it out it started 2nd pull, didn't even change the petrol. Now in my garage, been there 3 years, might give it a look today, expect the same result.
    mmm yes I would expect that from a Yami... but these Merc's take a little more tinkering... (IMO)

  9. #9
    Tremlett 15's Avatar
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    Quote Originally Posted by RIN View Post
    It has 7.5 on the side but no "s" It has two cylinders, no kill cord, I think you can track the age from the serial number so I'll have a go at that.

    Will report back tomorrow evening


    post or pm me the serial No. I have a list that covers most Mercs or a photo of the decals as I also have a decal list for engines upto 1985.


    example
    added.... 1985 decals 7.5hp

    Last edited by Tremlett 15; 18-03-10 at 08:48. Reason: adding photo

  10. #10
    NickRobinson's Avatar
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    Default fuel and spark, spark and fuel....

    I agree with most of the posters, but wouldn't put penetrating oil in the plug holes of an unseized engine.

    Remove the plugs, fit them on the leads and get someone you hate a bit to hold them against the block while you briskly pull the cord. ( Probably how morris dancing was invented-)

    Got two sparks? Pour a table spoon (not my tablespoon!) of petrol or 2 stroke into the plug holes, replace plugs and try to start, no choke at this stage.

    It'll cough and run, as it dies, apply full choke.

    Have full and enjoy exercise, you will warm up first? (not the motor...)

    My 'best' one was a 6hp Perky my son found in a neighbour's hedge. Both coils crusty/dusty (ie dead) so we ran it off two 12v car coils and a non charging car battery...

    Did Coniston fine!

    Nick

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