Thread: Yamaha 225 SHO

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  1. #1
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    Yamaha 225 SHO

    I just blew my 225 SHO up one week ago. It just hit 300 hours, and I had my Yamaha dealer perform the 300 hour service on it. Then.........it slung a rod through the block. Fortunately, it is under warranty.

    It seems that there is some history of these engines self destructing. I am just fishing for information. If I am right that these engines have some history of doing this, what is the general opinion of why they have this issue. Or, am I wrong, and they have provided excellent service and longevity.

    I appreciate any input.

  2. Member
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    #2
    Hmmmmm. I must have asked a naughty question. All I wanted to know is in general, what is the cause for the majority of the 4.2 SHO powerhead failures. Right, wrong, or indifferent.

  3. Member
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    #3
    i would like to hear what is said about the 225 also. just got a new skeeter zx225. and did alot of research and mostly only seen good reviews about the 225. hope im not wrong..
    Chris
    2019 Skeeter zx 225

  4. Member
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    #4
    18 Month old 250 SHO cracked something at 130hr, water in the oil.
    They did not specify exactly what failed.

  5. Member
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    #5
    Quote Originally Posted by friogatto View Post
    18 Month old 250 SHO cracked something at 130hr, water in the oil.
    They did not specify exactly what failed.
    Would be interested to hear what is found. What year?
    Lake&Bay Boca
    SHO

  6. Member
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    #6
    Quote Originally Posted by jeff7y28 View Post
    I just blew my 225 SHO up one week ago. It just hit 300 hours, and I had my Yamaha dealer perform the 300 hour service on it. Then.........it slung a rod through the block. Fortunately, it is under warranty.

    It seems that there is some history of these engines self destructing. I am just fishing for information. If I am right that these engines have some history of doing this, what is the general opinion of why they have this issue. Or, am I wrong, and they have provided excellent service and longevity.


    I appreciate any input.
    It seems that there is some history of these engines self destructing. I am just fishing for information. If I am right that these engines have some history of doing this, what is the general opinion of why they have this issue. Or, am I wrong, and they have provided excellent service and longevity.

    There is enough stuff just here on the BBC to fill up a big book about this subject. I purchased a 250 Sho a couple of years ago that at that time had around 60 hours on the new factory powerhead replacement. From what I've been able to learn it seems the problems have been centered around two issues. The original powerheads had a bearing design problem that Yamaha to their credit took care of, even on many motors that were still running well. I think the new bearing design in the new powerheads have proven to be reliable and the solution. The other major problem is the engine's tendency to "make oil" which is really blow fuel past the piston rings and dilute the crankcase oil thus raising the oil level. Most opinions seem to be this is caused by a combination of these factors: 1) All 4 stroke outboards are liable to make oil, at least until the rings seat 2) Our Sho engines run a very low oil temperature, I think at the most 147 degrees or so and that only with a long WOT run. This low oil temp is not enough to purge the fuel content out of the oil and I would add it is concerning about moisture as well. I've read that the new Merc 4S runs 250 degree oil on up to as high as 277 degrees. I'm no engine engineer but oil temps that high would concern me as much as too low but that is another brand and subject. My engine runs great and doesn't seem to make any oil. I now have about 85 hours since the powerhead was replaced. What concerns me is some reports I've seen that say an engine that stops making oil can start making it again if you idle around too much as in graphing a lot. Maybe this goes back to the Sho design that uses plasma hardened cylinder walls instead of sleeves. The plasma hardened wall is very, very hard which should make for long life but perhaps doesn't work well with the ring material / hardness being used. What is concerning about the possibility our engines will start making oil again is the effect that oil that is diluted by a solvent (gas) will have on bearings. Just guessing but maybe that explains why we still see reports of well maintained engines that supposedly were broken in that without warning blow up. I don't know but now you're up to speed on the Sho engine, at least what I know. I love my Sho and plan to keep it a very long time. I try to follow the book about care and I'm especially particular about letting the engine warm up before running over 3000 rmp and allowing it to cool down after a run. I also about every three or four times out try to make a run at 5500 rpm or over for at leat a couple of minutes. One last thing - I believe in Ring Free plus in every tank of non-ethanol 89 octane fuel. Disclaimer - I hope no one will take offense about any of this. I love my Yamaha and would buy it again. These are the facts as I understand them and I welcome any and all input including corrections if I have something wrong.

  7. Member
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    #7
    My 250 has about 400 hours and has been flawless.

  8. Member
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    #8
    The majority of the power head failures you've read about are from the faulty bearings in the early built ones that choochoosnakeman mentioned.

    But your motor falls under the "shit happens" category. Boat motors just blow up. All makes and models. You're asking a motor to turn 5-6k rpm on cold starts and short burst where the oil never gets up to proper temperatures to protect moving parts. Then it'll sit for weeks or months letting the oil film dissapate so the next crank is essentially dry. Pretty much normal bass boat motor operation is a long list of everything you're not supposed to do to keep a motor together for a long time.

  9. bullyfish
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    #9
    Expensive over engineered piece of junk if you want something reliable put a Suzuki or Honda on it

  10. Member chrisansilver's Avatar
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    #10
    Quote Originally Posted by BULLYFISH View Post
    Expensive over engineered piece of junk if you want something reliable put a Suzuki or Honda on it
    No thanks, I’ll stick with the over engineered junk...
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