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Thread: props

  1. #1
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    Default props

    Ooh, my first post to Boat Racing facts. Maybe I'll learn something.

    I have a few questions on a Merc 60J. I'm assuming 6 hp. What kind of rpm did the 60j run at? What were the speeds? Was the 60J ever a viable J class motor? What props were used on the 60J Merc?



    Oh, thanks to everyone for the "new" site !

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    Sam Cullis Mark75H's Avatar
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    The 60J was the J class motor from 1968 until the OMC 15ss with restrictor came along. The powerhead is basically stock, so I'd assume 5,500 rpm. Speeds were in the 30's to around 40.

    There were special props for the 60J, but there were also adapters to run other props, I assume the same props that had been used on the previous Mk5 and Mk6 Mercs from the previous generation.
    Since 1925, about 150 different racing outboards have been made.


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    Any guess what size props they ran? And are current J speeds above what the 60J did? thanks

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    Sam Cullis Mark75H's Avatar
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    Current J speeds are a little above what most 60J's ran, but I think I saw a 60J run at Camden a few years back. It would be an OK starter motor, but I doubt they would run at the front on most boats.

    The 60J props I've had my hands on didn't have any numbers on them. Ron would know more about what pitch to use.
    Since 1925, about 150 different racing outboards have been made.


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    G&M Racing mercguy's Avatar
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    Quote Originally Posted by Mark75H
    Current J speeds are a little above what most 60J's ran, but I think I saw a 60J run at Camden a few years back. It would be an OK starter motor, but I doubt they would run at the front on most boats.

    The 60J props I've had my hands on didn't have any numbers on them. Ron would know more about what pitch to use.
    hmmm.......

    60J- 6hp+
    15hp Merc restricted - 10hp+
    OMC 15A restricted - 10hp+

    I do not think the 60J would stand a chance, even against the slower Merc 15, which is still slower than the OMC 15, both motors being restricted......in the J class.......
    Daren Goehring
    63-R
    DSH, 500ccmh, 750ccmh


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    so, what kind of rpms are the OMC and Merc J turning today? and how fast are they? thanks.

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    Sam Cullis Mark75H's Avatar
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    The J hydro kilo record is 42.75 mph
    Since 1925, about 150 different racing outboards have been made.


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    Default 60j Props

    Quote Originally Posted by hydroplanes
    Ooh, my first post to Boat Racing facts. Maybe I'll learn something.

    I have a few questions on a Merc 60J. I'm assuming 6 hp. What kind of rpm did the 60j run at? What were the speeds? Was the 60J ever a viable J class motor? What props were used on the 60J Merc?



    Oh, thanks to everyone for the "new" site !
    Back around 1980 several front running JSH's were using ASH props of mine from 10 years earlier. Basicly 6 inch diameter and 9 inch pitch.

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    I see some mod guys claiming 10,000 rpm. Are they running 1:1 gears?
    How does a prop hold up to that kind of rpm?
    thanks

  10. #10
    Sam Cullis Mark75H's Avatar
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    10,000 rpm or more with a mod? Probably not. 9,300, 9,400 with a C Merc mod maybe. 40's and 44's seem to stick at 8,400

    Alkies do run 10,000+ maybe 12,000 or more, but most use at least 7% reduction, some 30% and fairly small diameter .... 7% gives 11,150+ rpm with 12,000 going in ... sounds like that is still the propshaft rpm range you are thinking about

    I don't know what the exact maximum tip speed is in mph or ips, but at high rpm you have to keep diameter down to avoid excessive tip speed or all you get is blow out (pure, true cavitation - boiling water due to the pressure drop, just like in refrigeration )

    If you are going to pull mucho propshaft rpm, you are going to have to keep the diameter microscopic, esp without mucho hp.
    Since 1925, about 150 different racing outboards have been made.


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