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Johnson 200 shuttering above 4200 rpms

SnapperBlues

New member
Hello,

I have a 1990 Johnson 200 looper (J200TXESM) that I worked to get back in service last year. I purchased the outboard from a gentleman that had it sitting for 5 years for 200 dollars.

I diagnosed and replaced the:
Stator
Flywheel (incorrect flywheel - they had a counter rotating on on it)
Powerpack
all 6 coils
plugs (new champion ql77jc4)
Thermostats
water pump
rebuilt all 6 carburetors
replaced lower unit fluid
Replaced VRO with another I had that already had oil delete (premix in tank)
Plug wires (replaced with the 9 foot long CDI wires ugg)

New Johnson fuel/water separator along with new gas lines from tank to outboard and new primer bulb.

From my research, these are low compression engines, my measurements are as follows:

76,76,82,80,85,85

My mechanic said that these numbers were fine and he has seen them run well at 70 psi as long as all were within 8 - 10 psi.

The engine runs great, have run it all day under 4K rpms and no problems at all.

If I run the engine above 4K rpms, more like 4200 to 4500 for 90 seconds, it falls off plane and shutters. It still runs, but when I throttle back up, it shutters and wont pass 2,500 rpms.

In checking the temp, the heads are all just about 152 to 155 degrees.

If I let the engine sit for 10 minutes, fire it back up, it runs fine again then repeats the same issue once above 4K rpms.

The only thing I have noticed is that a lot of fuel is spitting out of the exhaust at times and when priming with the primer bulb, It is hard if not impossible to get the bulb to become firm.

When inspecting my tank, I saw no leakage and there were no fumes. I am thinking that it is either:

Bad powerpack from CDI;
gunk in gas tank;
bad fuel pump (diaphragm looked fine)

I have all the proper testing tools and factory manuals. I have checked the timing and voltage from the powerpack, stator, timer base and coils all within the CDI specs.

Any thoughts. This one is breaking me.
 
Last edited:
Are you taking these voltage readings while/when this problem exist?
Are all six throttle plates opening all the way?
Disconnect temp switches and rerun.
 
Are you taking these voltage readings while/when this problem exist?
Are all six throttle plates opening all the way?
Disconnect temp switches and rerun.


Voltage readings before and after. Both within the CID numbers. Throttle plates are synced and opening all the way.

Tested with both temp switched disconnected already.
 
They had a counter rotating 1988 flywheel. That 200 actually ran backwards. Took some time to diagnose that issue. Realized it when I looked at the trigger points when taking the flywheel off.
 
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