Thread: Johnson "70mod"

  1. #221
    Team Member hupiveneilija's Avatar
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    1st pic is what you get for too much ign timing. 2nd when it breaks headgasket and leans mix and over heat piston.
    But nothing that cant be fixed. Little solid hone use and new used piston, off you go!

    It can tolerate quite much timing adv. with 1.5mm gasket compared to 1mm. When i get this back together have to check timing and take it 2* lower 'cause it worked good with that. Part of it because i dont have high comp pressure.

    And i use copperhasket spray, dont know is it good or bad.
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  2. #222
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    when you say
    Ive got 1.5 to1.9 in fullspeed and motor is 40*c after wot run.
    do you mean 1.5 to 1.9 BAR water pressure ? if so thats perfect. (21 psi to 27 psi) that is ideal pressure.

    you need a thermostat to keep engine running at the right temperature, or you will destroy the block by running too cold.

    timing at 17 to 19 is good, no more or it will again ruin the pistons and rings.

    what is compression on this engine now , cold cranking on starter with no added oil put in the bores ?

    what is your maximum rpm so far with this motor ?

    40 deg c is way too cold, and you will be losing power.
    if on the newer ignition you wont even be out of quickstart mode at 40c. that is only 104 f !!!!!

  3. #223
    Team Member hupiveneilija's Avatar
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    Yes BAR is the unit. I have to limit waterflow some how to get temp up a little that said put stock spring on thermo/pressure relief and take spacerplate away.
    I have thermostat in place but dont know how much water pressure is too much for the motor.

    And yes 40*c is way low for temp.

  4. #224
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    these can run at 40 to 45 psi water pressure no problem.
    you used to get 2 gauges from omc zero to 30 psi and zero to 60 psi. that would be zero to 2 bar and zero to 4 bar.
    so you are fine with water pressure..
    remember if there is a bit too much there is also escapes built in the system for that, in the front of the leg and in the adaptor.

  5. #225
    Team Member hupiveneilija's Avatar
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    Okay, first; Do not use copper spray with headgasket!
    I think it caused that water problem yesterday and before. When i took gasket off surface felt kind of a slippery what makes little leak, now without spray no problem.

    2nd. Went ramp today to warm the engine so i can retorque bolts. With 1mm gasket in place and 21* ign timing, yes i know now that it can manage with something like 25* with 1mm gasket and more with thicker, dont ask HOW i know��. Didnt hear any sounds that dont belong there when made full throttle pulls with testprop and also in went 1.5mm~59 jets, up from 56.
    Sounds nice��.

    For the cooling. In place is thermostat, stock reliefspring and no adapterplate between head and thermcover.
    Water pressure at idle is 0.6bar and 5000rpm 2bar. Warms pretty quick on idle to ~70*c and when made those wot pulls its ~50*c. Temp measured on head surface.

    Looking forward tomorrow , going out if the wind is low enough. We have had crazy winds last 6 days yesterday approx 15to23m/s.

  6. #226
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    Hope you have a good run with motor.

    those Jets is that with the smaller carbs or the bigger carbs ? ( bigger being 1.5 inch throat at the back )

    50deg on full throttle is not too bad , 70 at idle is a little bit warm but not too much.


    I know what crazy weather is like, 2 weeks ago we had 32 deg C then 4 days later everyone wearing winter clothes !!!
    temp went down to 14 deg C within 2 days, realy crazy and then high winds and rain.

    we are now forecast some good warm weather but maybe thunderstorms , no good for boating.
    I am hoping to get out myself either Friday or Saturday if weather permits.
    I need to test a couple of propellers to see if my idea has worked to raise bow.

  7. #227
    Team Member hupiveneilija's Avatar
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    To LC and Hevi Kevi, there is a chance that those 72 jets with 1.5in carbs were too small for starters. Have to try bigger jet when everything else is working. Thumbs up!
    When i went testing them the engine behaved like what i tought was over rich situation but must have been other ways. MY bad! So naturally i went towards leaner wich i hope now was wrong way. But like i said have to give them a new chance.
    Dont know for sure if they are from 75hp or older 2cyl but definetly need big jets, like you said that have run 78 with no problem.

  8. #228
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by LittleCharger View Post
    You can hear if you know what you are listening for but most of the time people find out to late lol..
    This is SO TRUE!

    Now i know what to listen!

  9. #229
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    what carbs and jets were on the original motor you were running before you made nose cone ?

  10. #230
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    Quote Originally Posted by filthy phill View Post
    what carbs and jets were on the original motor you were running before you made nose cone ?
    These 1992 70hp wich are in place now. 50D.

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