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  1. #1

    Default 8hp Mercury faster prop

    Hey guys I got a 8hp 2 cylinder 2 stroke Mercury from the 80's. Can't remember the exact year. Anyways I run it on my 8ft sea flea and it has no trouble pushing me along the motor doesn't bog at all. It runs about 22mph. I was wondering if there is a different prop I could get for it so I could get it moving faster. If I can does anyone know what I would need to gain more speed? Thanks for any input!

  2. #2
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    9,114

    Default Re: 8hp Mercury faster prop

    Nope - at least not any speed you would notice.

    If you have the factory OEM prop it will be a 9 pitch.

    Michigan Wheel and Solas makes a 10 pitch that will fit but going to the higher pitch also drops your max rpms plus the prop bites harder and "slips" more (slip is present in all props and not something you can mitigate).

    I have tested 8P, 9P, 10P (3 blade) plus a 10P 4 blade on a 9.9 Merc (1986 model) and under the same conditions (swapped all the props at the lake, so all testing was within the same hour or so - as scientific as you can get in "real life") and the results (gps - only myself on my 14 foot aluminum) were "all within 1 mph" - which is almost a rounding error.

    If you want more speed, and can tell you now 22mph from an 8 horse is awesome, strap on a 15 or 20 horse (even going to a 9.9 might only give you 2 more mph).

    There is essentially "nothing" you can do to that 8 horse to gain "speed you will notice", unless your only goal is to see 22.2mph on the gps instead of 22.0mph.

    You can replace the exhaust plate and tube (one unit), retro-fit a new water tube (because the old ones will not fit the new plates and you have to drill out the pass through hole in the exhaust housing for the new tube to fit) and then replace the carb with one from a 9.9 and you will improve your top end speed by about 7% (1.5 mph on flat water with no wind). And yes, I have done the conversion for more than one motor - some guys don't mind spending 300'ish bucks - at least the last time I source parts - to be "faster".
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  3. #3

    Default Re: 8hp Mercury faster prop

    I have a Mercury 6hp twin merc 60 motor. The motor runs but when I put it in gear the boat does not move . I removed the propeller but I can't see anything wrong. Any suggestions?

  4. #4
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,706

    Default Re: 8hp Mercury faster prop

    possible spun hub inside of prop.With engine shut off shift and listen to l/u for click in gearbox.

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