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Exhaust Plug Corrosion: Can Engine Hours Predict Case Corrosion Risk?

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  • Exhaust Plug Corrosion: Can Engine Hours Predict Case Corrosion Risk?

    Hi, newbie here. I am considering buying a boat with a 2004 215 hp 4 stroke "Johnson" (Suzuki) engine. (J115PL4SR) The owner claims ignorance on the notorious exhaust plug corrosion issue and the stock plug is in place. (But he also claims regular maintenance by trained techs who would seem likely to know about such matters. Color me skeptical. ) The more I read about this issue, the more freaked out I get about potentially buying a boat and having the engine essentially become an expensive anchor due to this problem.

    Is there any number of engine hours beyond which I should not get this boat because the odds of the case being corroded is high?
    Is there a "safe" number of hours where corrosion is not likely?
    (I'm happy to replace the plug but if the surrounding case is corroded such that it stages for a catastrophic failure, that seems like a waste of time.) 300 hours? 500 hours? ____ hours?
    f the case is not corroded and you replace the steel plug with an anodized aluminum one, is that a long term fix or are you just delaying catastrophic corrosion for a while?

    Note that the engine has no hour meter and I am attempting to arrange for a tech with the Suzuki SDS system to determine engine hours and any history of error codes when we meet to test the boat on the water next week. (So far can't find anyone in the Phoenix area who can do that, recommendation welcome.)

    Thanks for any info or help anyone can offer!

  • #2
    Karasu, I believe hours are not the major contributing factor. I brought a 2002 DF140 with over 2000 hours and simply got a hex socket and undid the old steel plug and replaced it with an alloy one i turned up, but i have also read on this forum engines with as little as 300 hr having to replace engine holders because of the corrosion. Things like is the boat moored in the water, aluminum hull or glass, lots of use or little use.


    • #3
      I have a pair of 2003 DF140's with 2,200+ hrs on them. I replaced the plugs last year at 2,100 hrs. When I pulled the old steel ones out, inspection of the the casting showed a little interior erosion, but not enough to cause any concern.

      Aluminum plugs were installed as replacements and both motors are continue to run fine.

      If I was considering the purchase, I would ask the owner to pull the plug and allow your visual inspection of the casting. With a penlight you will be able to ispect the threads an see a limited amount of the exhaust chamber.
      Last edited by Ole Joe; 10-06-2018, 09:30 AM.