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  1. #1

    Default 1 clean spark plug

    Have a mercury 225 opti with 49 hours on it. Life challenges left boat sitting for 8 years. Starting to get it ready to run again. Pulled plugs and one plug looked like it was out of the box. What could have caused this or what should I look at before I try to start motor?

    The engine ran great before storage

  2. #2
    Join Date
    Sep 2010
    Posts
    21,182

    Default Re: 1 clean spark plug

    A clean plug results from , a bad sparkplug , no fuel , too much fuel, no spark or zero compression.-----I would start with a compression test and a spark check.----Good spark is considered to be able to jump a gap of 3/8" ( 1 cm ) or more.

  3. #3
    Join Date
    Jun 2013
    Location
    Duluth Mn
    Posts
    4,074

    Default Re: 1 clean spark plug

    Good advice and hey.......BE SURE TO PUT IN A NEW WATER PUMP IMPELLER!!!!
    Drain all old fuel and flush lines with fresh clear non oxy fuel. You certainly don't want to use ethanol with your operating schedule.....it has VERY short life.

  4. #4
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    6,102

    Default Re: 1 clean spark plug

    I would do an oil pump prime 2x's and put water to it and run it..... Once you have a heat cycle or two then check it over.....
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  5. #5
    Join Date
    Dec 2020
    Location
    Central Pennsylvania
    Posts
    6

    Default Re: 1 clean spark plug

    Water intrusion into a cylinder can actually steam clean a spark plug. Perhaps you have had a slight leak for some time but not enough that you noticed a change in performance.

  6. #6
    Join Date
    May 2013
    Location
    TX.
    Posts
    549

    Default Re: 1 clean spark plug

    Quote Originally Posted by ddc11 View Post
    Water intrusion into a cylinder can actually steam clean a spark plug. Perhaps you have had a slight leak for some time but not enough that you noticed a change in performance.
    That's my thought. With only 45 hours when you put it away, one wouldn't think that salt water passage pitting/corrosion would have been the cause. I had a water intrusion engine once before and it is amazing what water can do in a combustion chamber....as long as combustion is present....steam cleaning personified.

  7. #7
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    6,102

    Default Re: 1 clean spark plug

    Quote Originally Posted by Texasmark View Post
    That's my thought. With only 45 hours when you put it away, one wouldn't think that salt water passage pitting/corrosion would have been the cause. I had a water intrusion engine once before and it is amazing what water can do in a combustion chamber....as long as combustion is present....steam cleaning personified.
    A 2 stroke with water in the cylinder will trash the crankshaft in short time.... Doubtful that he has a water issue...

    There is a chance the cylinder liner is out of position but it is not likely.....
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  8. #8

    Default Re: 1 clean spark plug

    So just to clarify, the engine likely had the issue before storage? But hasn't ran yet? Was it winterized?
    I would swap the ignition coil from another cylinder and see if you're now getting spark to that clean plug. I've had this issue on Optimax.

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