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  1. #1
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    Need Help Jetting and timing '86 Johnson GT200STLCDR

    I bought this Johnson last year on a Hydra-Sports 20' bass boat. Spent a year restoring hull and re-wiring. Now on to the motor.

    The motor had a rebuilt flywheel on it, but I replaced (all CDI) stator, timer base, power packs and rectifier, which had previously caught on fire. now has good spark on all 6 cylinders.

    compression: #1 105 psi, #3 110, #5 105, #2 115, #4 115, #6 110

    New Champion QL77JC4 gapped @ .040

    All new 3/8 fuel lines from tank to vro plus added fuel/water seperator. all new lines to carbs and re-circulating system. flushed manifold drains and check valves w/alcohol, replace check valves not working

    rebuilt VRO pump w/OEM kit
    rebuilt carbs kits #0439079
    new OEM thermostats w/diaphrams
    New Boyesen power pack reeds
    did lync & sync twice
    new water pump kit OEM & adjusted shift rod to 21 15/16" per service manual

    The air box was gutted when I bought it, with just spacers. I found a used airbox baffle and was wondering if to install or not.

    The carbs are big bore, venturi measured 1.650", #397340. the side plates on the mixing chamber is 398020 , blank and 398021, although I can't see any difference. They are all jetted the same - low air jet .020, intermediate .000 plugged, fuel jet 76D

    The service manual says (I don't tust it) timing should be 14 deg BTDC. idle 8 deg ATDC

    I am new to 2-stroke outboards, but can turn a wrench. I am also going to do a coolant mod as i saw posted by 'Racer'

    Sorry this is so long a post. Thanks in advance

  2. #2
    Join Date
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    The OEM air box is quite restrictive compared to the version that replaced it.
    Your jetting will be pig fat rich w/it installed but would be close w/the later/better box.

    I doubt youll get away w/plugged mids on a heavy bass boat unless your always WFO.

    Great old motors when solid and well tuned.

    Be careful w/props too.
    They have more RPM than low/mid range torque.

    A 24 Raker may be a bit stiff dependent on load.
    A 22 may be a bit light but the boat would probably love it w/a heavy load.

    RPM will not hurt it.

    If your new packs have 6700 limits (the old ones were 6200) Id target 6500 and let er eat!

    Be careful though, big bore carbs on a heavy boat, w/too much prop, is recipe for disaster and why they were only used for 2 yrs.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  3. #3
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    thanks Instigator. so I should leave the airbox gutted. what about the jetting and timing? the prop is 13 1/4 x 25 4 blade just had balanced and reconditioned. too much? thanks

  4. #4
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    Being only 13 1/4” dia will help a bunch.

    Clearly it was jetted for the gutted box.
    As is, I doubt it will idle or plane.

    I havent looked at #’s, but if they truly are 1 5/8” venturi big bores, you probably wont like them on your rig.
    I’ve tuned them and made them work on everything that most thought they would not but not comparable to the latest mid bore carburetors.

    They are notoriously lean in the mid range which you bass boat guys spend most of your day and will likely kill it.
    If the motor lives youll hate the gas mileage at how rich youll have to jet it to live.

    Timing sounds good although I set idle by ear.

    The 225 carbs (now called mid bore due the big bores being eliminated) that Came out in I think 96 are by far the best and most tunable.
    You can tell that era of car by looking at the front of them.

    They have an allen head adjuster screw for idle setting that is recessed into the face of the carb.
    Ones before that had slotted screws (and sucked) and before that had what you have now which is a replaceable,fixed jet.

    I am impressed that you spent the money and time to do as much for this old jewel as you have.
    Most try to Run it as is and then bitch when the 40 year old ignition doesn’t work and they do not understand lync and sync :-)

    The next step is the most critical to get it to live and that is tuning and set up.

    Many, many before you have done what you’ve done, thought they knew what they were doing and fried it the 1st mile down the lake!

    They then buy a Merc and spend the rest of eternity bashing OMCs, cuz, its the motors fault ��

    What I will warn you with being new to two strokes is the margin of error for tuning on the last 10% is microscopic, and catastrophic if you get it wrong.

    Likely you won’t know it until the motor shuts off.

    )If it were me I would find that new era of 225 carbs and replace your airbox with that style as well. You will get a bonus of a five or 10 pound weight savings as well.)

    Or saws itself in half.

    Trust me, I know of, which I speak!
    Used to have a garden full of dead parts/failed experiments.
    Last edited by Instigator; 10-18-2021 at 01:01 PM.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  5. #5
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    Thanks for the repy Instigator. Alot of good info I can use. will start looking for those mid-bore carbs, looks like they were used on the ocean pro/ocean runner circa 1996 to2000. will I have to change the throttle bodies as well?

    I bought this to use as a flats boat for fishing on the Manatee river and the intercoastal bays in and around Bradenton. Not looking to go fast , just dependable . no need to burn it up. I know these old johnsons are strong and dependable when maintained properly. After all this GT is 36 yrs old, respect your elders.

    will post more as I progress. Thanks, Rich
    This where I'm at so farClick image for larger version. 

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  6. #6
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    just fyi i got a 96 200 or 225 in trade the other day. Haven't gone through it to say its a runner but would sell the powerhead cheap if interested. Id say whole motor but its a 25inch pig

  7. #7
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    thanks Revenge. how much for motor complete

  8. #8
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    I can pick-up

  9. #9
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    im up in RI. Are you taking a trip up north? if so id let the whole thing go for $1200

  10. #10
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    revenge 22, thanks for getting back. I'm going to pass. my brother is in CT and could pick up but I found the carbs here in Florida. thanks

  11. #11
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    no worries good luck!

  12. #12
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    To follow up:

    I would change throttle bodies and all.
    Once youre used to it, its a 15 min job.

    To convert, properly, besides new era air box and carbs, youll need the throttle/shift cable bracket (yours is in the air box base which youre deleting) and the timing pointer, (also on your base) it really cleans up the powerhead.

    W/those Carbs, if you take your time, you can tune them to where they only smoke when started cold, and once warmed up theyre virtually smoke free and they’re great on gas and carburete cleanly through the full rev range.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  13. #13
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    I should add, probably even bigger than the performance advantage of the new air box is, it removes w/no tools compared to your existing.

    Two thumb screws and youre done.

    Realistically, its off in 30 seconds!
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  14. #14
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    so i assume that V6 i got in trade has the newer carbs being a 96' correct? ive got the old style air box on my fishing boat now... might be a nice upgrade didnt realize they were that good. Looks like around 1995 is when OMC did sweeping changes in carbs/tuning to get these to run as well as the Japanese competitors. The 130 v4 looper comes to mind. with the newer carbs, they run so much nicer than the older ones.

  15. Likes Instigator liked this post
  16. #15
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    Instigator, thanks again. am working to find them. Great info

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