Omc 120 3000 Rpm At Full Load?

Discussion in 'Sterndrives' started by H180DSC, Sep 22, 2009.

  1. powerabout
    Joined: Nov 2007
    Posts: 2,903
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    A Mercruiser 120 which is the 153cu in chev like yours has a full throttle operating range of 3900-4300
    So you want over 4000 with a lightly loaded boat.

    Did you look at the mechanical advance in the distributor as Frosty mentioned?
    We need to know the sterndrive gear ratio to determine how the 15" prop will perform.
    I would guess a 15 prop on that boat would get it over 4000rpm depending on the drive ratio..

    Sorry..that engine photo is not yours is it?
    Can you post one
     
  2. stanl
    Joined: Aug 2010
    Posts: 14
    Likes: 2, Points: 0, Legacy Rep: 28
    Location: portland,ore

    stanl Junior Member

    hello powerabout,the motor runs pretty good for bein such an girl,oil pressure is never below45 and 55-60 at 3000 rpm, my concern is overeving.in addition to this WOT question, why is it i cannot find a SEASWIRL home page or archives that give info on thier product?i live here in PORTLAND,OREGON and from what i can figure ,they are built right over MT, HOOD in madras,ore. ENGINE MODEL#990242D,,,, OUTDRIVE MODEL#981110, SERIAL#W153435,,again thanks for the help,,,,,,,,stanl 4000rpm wow
     
  3. stanl
    Joined: Aug 2010
    Posts: 14
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    Location: portland,ore

    stanl Junior Member

    stanl here,here are some pics of my 1978 seaswirl,you mention MERCRUISER in last reply ,,i thought was a ford product,i know nothing,but i do know i have a chev. thankyou again for your replys,i am learning everyday.,,,,,,,,stanl
     

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  4. stanl
    Joined: Aug 2010
    Posts: 14
    Likes: 2, Points: 0, Legacy Rep: 28
    Location: portland,ore

    stanl Junior Member

    stanl here again, with more pics. is the engine that was nicknamed "the iron duke"??? must be fun scootin in and around three different countrys,what do you do?,,,,,,stanl
     

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  5. powerabout
    Joined: Nov 2007
    Posts: 2,903
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    The package will last for years as long as you flush out the sea water after use and the stern drive is full of oil.
    The engine is OK to run at 4500rpm all day.
    Re the performance issue have you
    1. used a timing light to see if the mechanical advance is working
    2. remove the flame arrestor and open the throttle fully to see that the butterflys are vertical, i.e. fully open
    3. make sure the choke is coming off when the engine has warmed up
    cheers
     
  6. Wassman
    Joined: Aug 2018
    Posts: 1
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    Location: Alberta Canada

    Wassman New Member

    Hi, I had same problem, changed prop to 14/11 now get full rpm and zero lag out of hole. Top speed 45kph at 5000 Rpm
     

  7. powerabout
    Joined: Nov 2007
    Posts: 2,903
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    Unless that boat is very heavy it should be going faster then that, 5000 is a bit too much when going that slow
     
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