Thread: Johnson "70mod"

  1. #311
    Team Member hupiveneilija's Avatar
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    Carbs from 70hp
    Block bp without comp relief holes
    Ex 1.382 45* chamfer
    98e5
    56kn with 2person=64.4mph
    27 i dont know but 25to26pitch yes. If going higher with propshaft then 27 is doable, atleast with 1 person load.

    That 2blade prop is somewhere 25-26 in pitch but slips more, still same speeds with 1 or 2. 3blade is more drivable. 2blade need more pitch.


    #1 145 #2 150 #3 150, retorque multiple time pays off! Have to get that 1mm headgasket, sierra 1.5mm in place now.
    All this 21* ign timing.

  2. #312
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    I would not have timing at 21. 19 max and that is more than the proper 17 deg.
    omc took it back to 17 for a good reason.

  3. #313
    Team Member hupiveneilija's Avatar
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    Ive done most things "wrong" including ignition timing and it still works, lucky me!😂😂

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    Lucky you ?

    Yeah right , you carry on writing it and one day it might all come true..




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  5. #315
    Team Member hupiveneilija's Avatar
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    Testrun today with those 1.5in carbs, now they work. Acceleration is even better now!
    With sligth backwind took 58kn so that didnt even realise first i was going so fast😂😂.
    From 50kn floor the pedal and can feel the acceleration to maxspeed.
    Now goes maxspeed with little less trim so there is more power.

    Got 1.6mm mains and i think #41 middle for jetting, might need going bigger from that 41. And maybe try 1.7mm main.

    I think if get rpms around 7500 with right prop then it goes even faster😉

  6. #316
    Team Member hupiveneilija's Avatar
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    Checked cold cranking comp, 150psi on every 3 cylinders. This is one reason to use heavy oil ratio, get good compression and proper lubrication for the engine. And therefore dont have to run too rich fuel/air mix to get it going.

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    so you have got normal compression now then ?
    nothing special about 150 psi on a fresh motor, especially if running loads of oil.
    that is just normal compression.

    what is the compression on your later 56 oval port motor with same gauge ?

  8. #318
    Team Member LittleCharger's Avatar
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    Quote Originally Posted by filthy phill View Post
    so you have got normal compression now then ?
    nothing special about 150 psi on a fresh motor, especially if running loads of oil.
    that is just normal compression.

    what is the compression on your later 56 oval port motor with same gauge ?
    I believe he has raised his exhaust port height so there is a difference

  9. #319
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    yeah ported I know, but your not taking into account it has tiny little 21cc heads ? 7cc less than a sst60 ???
    put those on a normal 56 and it would be crazy high straight away, so even with the porting of the exhaust this should be much higher.

    what is the cc of your heads Little Charger on the motor with the high compression you posted a pic a week or so ago.in the 190psi.

  10. #320
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by filthy phill View Post

    what is the compression on your later 56 oval port motor with same gauge ?
    If you mean that on the summer cottage, dont know.

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