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Thread: Any up-date on high compression pistons in 59 cu. In. Mercury?

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    Question Any up-date on high compression pistons in 59 cu. In. Mercury?

    Awhile ago there was a thread on performance improvements for the 40 and 60 horsepower 59 cubic inch Mercury. A fellow had manufactured replacement pistons that increased the compression. Were the pistons ever produced? If so how did the motor run and did it require any other changes to go along with the change in compression?

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    Why not? Instead of flat tops, the pistons could have a mild 'bump' in the middle (like 4 stroke high perf pistons).

    Hope they got made.

    Jeff
    "We live at the bottom of an ocean of air." - General Marvage Slatington

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    Jeff Dunn makes them he is on fb.
    According to him they make an extra 10 hp on stock motor .
    Some of the duck boat boys are getting well into the 80 hp range with ported motors
    Some guys are getting over a 100 but not sure if this is with nos or not.

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    Quote Originally Posted by fs5 View Post
    Jeff Dunn makes them he is on fb.
    According to him they make an extra 10 hp on stock motor .
    Some of the duck boat boys are getting well into the 80 hp range with ported motors
    Some guys are getting over a 100 but not sure if this is with nos or not.
    Thank you.. I found Jeff on S & F he is a major player in southern drag racing and has built some very fast tiller boats. One runs 73 mph with a mod 59 cu. in. Mercury. We hope to run T850 boats in drag next season. T850 is dominated by 56 OMC motors. It would good for the drag class to have the Mercury in it.

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    Default 52ci Merc with custom high dome pistons

    Here is a 52ci Mercury engine with custom, high compression pistons...

    https://tallahassee.craigslist.org/b...382567875.html
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    Now that is interesting. That fellow has invested a lot of time and money into the motor and prop to run mid 60's. There have been several bone stock 52 cubic inch Mercurys race in our FV class a few years ago on similar hulls. They ran low 60's. The bone stock 59 cubic inch Mercurys ran mid to high 60's on the same hulls. Sometimes people think they know more than the engineers who build the original motor and waste a lot of time and money to create their super motor. Many times the result is not as good as the dream.

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    I'm currently working with Jeff and have had the pistons in a 59" for about 2 years. Mine were milled to make 150 psi and work well for me, wanted to be able to run pump gas. Made 83 hp on a land n sea dyno and runs 72 with a worked 18 chopper on a cypress strip boat.
    Likes LittleCharger, hydrospeed77 liked this post

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    Quote Originally Posted by hightide View Post
    I'm currently working with Jeff and have had the pistons in a 59" for about 2 years. Mine were milled to make 150 psi and work well for me, wanted to be able to run pump gas. Made 83 hp on a land n sea dyno and runs 72 with a worked 18 chopper on a cypress strip boat.
    I am guessing your outfit is a tiller mod 40 Mercury. In the rules of our T850 class we allow the 60 hp 59 cubic inch Mercury. The motor has to be stock however they would be allowed to use an aftermarket piston to obtain 160 lb compression. Could you supply us with the piston?

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    Absolutely, we'd be happy to. We just got a shipment of stock bore and .020" over. They are a wiseco piston. Jeff can mill them to approximately 160 psi for you.

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    Thank -you, I sent you a message.
    Likes hightide, hydrospeed77 liked this post

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