Thread: Johnson "70mod"

  1. #111
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by LittleCharger View Post
    Yes you really need to understand what your doing when moving the transfers, a good block becomes scrap pretty quick. Generally just clean up on transfers. We use to turn in the 7's with a stock ported 56er with 160lbs compression with a nitro case and a 23 no problem, doesn't get much simpler then that.

    Sounds like swimming weather at 4 degrees. We don't run a thermostat after break in but have to monitor heat in the block when testing in the spring due to cold water.
    Thats true with transfers.

    Do You leave therm/reliefvalve all away? I opened that plastic core and took thermo element&spring out. Center portion flows now all the time and then have to find/make softer spring for the valve.
    Made those watercavity mods You see in a last photo . Those and this thermostat mod see how it works. Hope it flows enough.

    But wich reeds? Ccms or Boyesen? Have both.

    7*c YES! Its summer!

  2. #112
    Team Member hupiveneilija's Avatar
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    Putting powerhead together, degreed ex dur 180* and blowdown 29*

  3. #113
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    go and buy a new thermostat and the right spring and the new style cover. or you WILL destroy that motor.

    if the 56 is not at right temp she will die very quickly.
    do it right or you will be needing another block too.
    Even fast fred always says about getting the 56 upto temp before hitting the throttle, with no thermostat you wont reach correct temp in cool water. if in Miami then yes, in finland NO.
    with the right thermostat the motor will come upto temp in about 3 minutes maybe less.
    I start my motor up and by the time I have released the ropes and lit a cigarette she is ready to put into gear, another 30 second and the temp is perfect, then it stays good.
    even running full throttle I still keep around 60c degree in the winter, 65c in summer at 6300 rpm and heavy load. and will idle in gear all day at 70 deg c...

    you need minimum 50c deg to run without being too cold for the engine, ideal is about 60c to 65c deg on max speed.

    running too cold is just as bad as too hot ..

    56 is not good if its too cold, the clearances are not correct and boom, another engine block for the junk pile.

    leave the transfer ports normal and the boost, just raise the exhaust only.
    you dont know and understand 2 stroke enough, your allways thinking 4 stroke technology.

    get the normal head and shave 1.5mm then just put it on, then put it on and go play at 7500 rpm and hopefully she will last a little bit longer.
    if you run at 8,000 then 20 hours maybe 30 if very lucky before needing re-build AGAIN.

    on my project engine I will only raise the oval port and shave the head, everything else will stay the same, including timing and the electrics. but I only want 6500 to 6800 rpm and engine to last long time.
    parts in the uk are very expensive, and I only use for fun not
    Likes midlandtuffknt liked this post

  4. #114
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by filthy phill View Post
    improved thermostat and housing and spring .

    .
    What do You think is improved spring?

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    it is a totally different rate of spring and just different type, different thermostat and also different housing.
    I have 2 styles of thermostat housing that are newer than yours, you cannot use the same spring in each housing cover, one is a cone shape and the other normal shape.
    But both are very different to what your housing takes.
    a pic below shows the thermostat cover is a very different shape to yours, its goes in not outward.

    if you look at the later style you will see that the cover is almost flat with the centre slightly going in, your cover comes out by a fair amount.
    if your going to be taking thermostats apart there is no point at all to even have one in there, then you can happily wait for the engine to destroy itself due to running too cold.
    too cold means the wear on the motor is going to happen fast, very fast.

    most people that run without thermostats are racers who have to re-build their motors in very short amount of running times anyway.
    if your prepared to keep destroying stuff then just dont fit the right thermostat and housing and newer water pump, let it stay the same as it is.
    the scoring of the top and middle pistons and sleeves was why omc sent out the bulletin, it happened to thousands of engines not just the odd one.
    Joe reeves even speaks about the problem and I think it is on this very forum..


    here below is 2 very different thermostat covers, and both of these are much later style than what you have. the springs will not inter change on these covers
    take a close look you will see the centres are very different !!! 1 has a centre with 3 small prongs the other has 4, .
    also a pic showing the complete breakdown of the parts.
    it is very different to the older versions. this is what omc service bulletin recommended to keep the motors at correct temperature.
    Attached Images Attached Images    

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    it is totally different to your thermostat spring .
    it is also the housing that is different, not just the spring, it is the complete unit.
    There is a large spring, small spring , thermostat, plastic housing , seal and the gasket and metal ring and poppet type thing, its complete different to older style..
    here are some pics to show everything.

    1st pic , notice the thermostat cover goes inward not out !!

    2nd pic, two much later types of thermostat covers and springs, not interchangeable.

    3rd pic, the breakdown of the complete thermostat assembly... very different to your older style thermostat assembly.

    .
    Attached Images Attached Images    

  7. #117
    Team Member hupiveneilija's Avatar
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    Went to testdrive today not white ph but with blue one. Made my speed record dont know what the engine rpm was but it was HIGH!

    Made spacer between thermostat cover and head , then softened reliefvalve spring as much as I could. With these and those drillings&grindings done to waterjacket, pressure is now at full speed around 0,9to1,2bar. Engine warms up pretty fast but there might be just too much flow at speed.
    Maybe put unmodified relief spring its place. After slowing down from wot head is aprox. 45*c from surface, could be higher.

    To LC: I put 56 jets and middle is 57. Plugs shown in picture.
    It feels really strong through hole revrange when on plane. And goes to plane with no drama.

    I have stock tuner on it but still it revs higher than I imagined. Went 56.4kn 2.42 gears and srx my own desing. Dont know max rpm because tachmeter stops at 7000.
    Attached Images Attached Images  

  8. #118
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    PLugs look perfect to me, propertan colour not lean and not too rich. ( but I am not an expert at reading plugs)
    on temperature I would seriously get the new complete kit and be safe. 45 deg is far too cold.
    your speed is fantastic. glad it s going so well for you. 56.4 knots is 65mph !!!! that is very fast on that boat and very fast on any boat

    did this motor have new rings ? or just the exhaust ports modified. and exhaust water passages ?

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    Old used rings and pistons. Oh and ig timing 17*. Think that head did the trick. Fellow who did it knows his business!

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    what is compression, cold cranking all 3 plugs out and NO oil put in the bores, cannot get proper reading if putting oil down the bores.

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