Thread: Johnson "70mod"

  1. #231
    Team Member hupiveneilija's Avatar
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    From left#1#2#3. This is after 10nmile, fullthrottle almost hole trip and wot last 1nmile.
    59jets and timing 22*. Temp from head surface after shutdown little under 40*c, thats too low have to get higher or what? But where to restrict the flow? And 2.5bar pressure wot or its where meter stops.
    Otherwise goes really nice, boat is 👌to drive even it was real choppy today.

    Went 54kn 7400rpm, awfull wind facing front.

    A friend of mine was riding along today with his Argo cat 21& 200xs Ros.

    Need more this! 😂😂
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  2. #232
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    54 knots ? that is pretty dam fast . it = 62mph .
    to get that with a head winds is extremely good, and 7400 rpm she must sounds very good too.
    photo shows the boat running pretty level,

    the 1992 carb , is that 1.5 inch throat or 1.25 inch throat ?

    on plugs no 3 looks to be best to me no 2 a bit lean maybe
    and what colour 2 stroke oil are you using ? .. clear...red...blue...green ?

    temp will be low if no thermostat fitted, too much water flow cooling it down, I would sooner have thermostat that restrict the flow any other way.
    because to get correct temp at high rpm the water pressure would be far too low at slow running and idle.
    with a thermostat it will be right all the time.

    glad it is running good for you ....

  3. #233
    Team Member hupiveneilija's Avatar
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    1.37in throat. Thermostat is in place, but those water mods done to the block increase flow quite much. Have to lessen it.

    I might leave #1 untouched and lean #3 little bit but first have to try with fresh plugs and see how they look.

    Blue full synt 25:1=3.85%

  4. #234
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    With the spark plugs I thought number 3 plug looks best, slightly rich, but best for high rpm...?

    where on the head are you taking the reading from ?
    do you have a gauge fitted in the head or use a heat temp infra red gun ?

    There is threaded hole in the head for the temp sender, it is on the right side of thermostat cover ( pic below)
    the sender can be bought from any auto parts store as it is the same as used on cars, then I just bought a cheap durite temp gauge and ran
    a single wire from gauge to the dash and a positive from other clocks, works perfect every time. and can see it when going along real easy.
    simple to fit and dont need to be real tight as it is a tapered thread on the sender and no water to come out of like on cars when fitted into water gallery/housings.
    the threaded area gives the temp of the head to the sender.

    this way you know what is going on all the time and at what rpms. with this and water pressure gauge everything on the cooling is monitored on the test runs.


    .
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  5. #235
    Team Member hupiveneilija's Avatar
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    Ihave pressure fitting there. 3mm hole on the bottom.
    Pistons after taking boat to trailer, few minutes of idling. From up 1,2,3. That is lower tr port.
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  6. #236
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    what do you mean 3mm hole ?
    are you saying you drilled through this area ?

  7. #237
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by filthy phill View Post
    what do you mean 3mm hole ?
    are you saying you drilled through this area ?
    Yep. Also have to use 8mm drill to get hloe deep enough for tempsender. Its now in contact with water. 4.5mm through hole now.
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  8. #238
    Team Member hupiveneilija's Avatar
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    DONE!
    My cockpit.
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  9. #239
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    This is why your seeing such low temp readings. you are not getting the temp reading at the right place !!!! you are measuring the water not the head !!!
    I have no idea what the water temp is meant to be on these, definitely not the same as head temp though.
    on a car when water temp shows 88C the head temp will be way over 100C.... so maybe if you read the actual head temp you might already be at the right place..

    think of the tell tale water, that never gets to 62c and that has come straight from the head ?? so water temp and head temp are 2 completely different things.
    water temp will only be the similar to the head in a closed circuit system like a car or motor cycle with radiator etc.

    next time I run my motor in the tank I will get temp reading of the head and temp reading of the tell tale water, I think it will be atleast 10c difference maybe more.


    The new complete dash is plain simple and easy to see everything straight away, I like that dash very practical for a fast boat..

    I like that 8,000 rpm tachometer, what make is that one ? is it a marine tacho ?
    and I see the pressure gauges too, they work pretty good, and I like how you mounted that.you have given me an idea with the pressure gauge mounting ha ha
    .

  10. #240
    Team Member hupiveneilija's Avatar
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    Water over the sender is like conductive material, it is not in a strait flow, see how it works. And that telltale is NOT coming from head, it comes from top of the block, 1st cavity under excover plate.

    Tachometer is quicksilver made by Tflex.
    Yes im very satisfied for the layout, simple and very readable. On the left i have RAM mount for 7in tablet as a plotter. Doesnt show on the picture.

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