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  1. #1
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    Default what makes an engine knock?

    i have a motor that sounds like its nocking... what exactly is doing the knocking in the motor. if i took it apart to fix the knock, what would i have to repair or replace

  2. #2
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    Default Re: what makes an engine knock?

    Need a better description. It could be anything..Poor fuel, bent or stretched connecting rod, bad wrist pin, wrist pin bearing, crank bearing, cam bearing, piston slap, etc, etc,....

  3. #3
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    Default Re: what makes an engine knock?

    it sounds like a knock and i just wanted to know what is required to stop the knock. its in a motor that parts are no longer made for, and 84 tohatsu... it knocks cause it was overheated by previous owner, i have since fixed the cooling problem and now it starts and runs easy and pumps and shifts, but it now knocks... too little too late, huhthanks

  4. #4
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    Default Re: what makes an engine knock?

    Could be alot of things. What grade of fuel are you using? You might want to try premium. It also could be carbon buildup - decarb. Another thing could be the wrong spark plugs or too far advanced timing.

  5. #5
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    Default Re: what makes an engine knock?

    you can hear the insides of the motor pounding against something in there, its pretty loud.... i knw its not the fuel, im using 89 octane with 50:1 synthetic oil mixture. i also know its not ignition timing. its a tohatsu, and the older tohatsus, the ign timing wasnt adjustable.id like to keep the engine, as it starts perfectly, but parts are no longer made for it any more. if i tear it down to inspect the insides, will i be able to tell if something was ou of whack? or if something is shot.......?im really afraid to do this as nothing is made for this motor any more and if i take it apart i wont be able to get new rings or bearings for it if need be.. or can they be made by wiseco or somebody, do i NEED to use oem rings? and can bearings be made by somebody else? if need be

  6. #6
    Master Chief Petty Officer
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    Default Re: what makes an engine knock?

    Topic: what makes an engine knock?
    When it's cold outside and you have the door locked.

  7. #7
    Admiral
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    Default Re: what makes an engine knock?

    Compression readings???And you said "if i tear it down to inspect the insides, will i be able to tell if something was ou of whack? or if something is shot.......?" Ahhhhhhh if you see a broken rod-------------

  8. #8
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    Default Re: what makes an engine knock?

    compression is an even 130 per cylinder, starts first pul, idels well, pumps water and runs cool to the touch for about 5 seconds....?

  9. #9
    Lieutenant Commander
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    Default Re: what makes an engine knock?

    The problem is you need to take this engine apart to find out whats wrong and you can't do this because you can't get parts. Even if you find that its just a squirrel caught in there you will need gaskets and what not to reassemble it. More likely you have a bad bearing or wrist pin and you won't be able to reassemble it. Are you sure you can't get parts? Don't they still make Tohatsus? All you can do if no parts are available is look for squirrels banging garbage can lids in there and hope for the best

  10. #10
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    Default Re: what makes an engine knock?

    they still make tohatsu's, yes, but they do not make the m8a anymore, nore do they make ANY parts for it at all... only option is if a dealer has had the parts on the shelf for last 20 years, they stopped making the m8a in 1985, and switched to the m8b in 1986 and on... i didnt know this untill after i bought the darned paperweight

  11. #11
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    Default Re: what makes an engine knock?

    You could tear it down and part it out on eBay. Your good parts should bring a good price if they are hard to find.

  12. #12
    Chief Petty Officer ziemann's Avatar
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    Default Re: what makes an engine knock?

    Just a suggestion-Give Twin City Outboard a call. They specialize in obscure and hard to get outboard parts. The web site is twincityoutboard.comThey have a giant bone yard of old uncommon outboards. They also have access to lots of after market and new parts. They would be worth a try. I know the m8a has been gone for a while, but it is not that uncommon. Good luck!

  13. #13
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    Default Re: what makes an engine knock?

    i have tried and they said notihing is availableanybody wanna buy a 8 horse paper wieght?

  14. #14
    Petty Officer 2nd Class
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    Default Re: what makes an engine knock?

    or anchor, I couldn't resist. I don't live to far from twin city outboard and if they can't help you i don't know where else you could go.

  15. #15
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    Default Re: what makes an engine knock?

    Run it 'til it grenades, then part it out.c/6Hooty

  16. #16
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    Default Re: what makes an engine knock?

    I'm guessing wrist pin. You could probably have one matched by an aftermarket company, or made. You can make your own gaskets for the tear down.

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