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2000 Johnson 200 HP Ocean Pro RPM low

C

carloliveira

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At full throttle turning a 14.5" x 19 pitch on a 21 ft Chapparal I'm showing 4700 RPM on the gauge and a speed of 28-30, all prop calculators are saying I should be at around 5200 rpm with a 19 pitch and somewhere in the upper 30s for speed. Besides a possible carburetor problem or a link and sync as well as a reed box seal maybe, has anyone else experienced this and if so what did you do to correct the issue? Thank you for your time.....
 
There are different ways to go about this.--------Perhaps the motor is running on 5 cylinders.-----------Test compression.----Check for spark on all 6 leads.-----------Or ask a shop to run it on a dyno to see if it is in good shape and producing proper power.
 
The spark plugs show evidence that all 6 are firing, if it were a spark problem I believe it would be running rather rough would it not? I'm gonna definetly check compression after warm up on the six cylinders
 
Had exactly the same thing...and as Racer says, it had dropped one cylinder.
It was however, a complex failure mode. The cylinder in question, #2, only dropped out after QS disengaged.
Very very weird. You would think it was the powerpack, but it actually turned out to be the timerbase.
I still have that TB, and can re-create the problem anytime.

The way I actually found it was I put new plugs in, and ran it. Number two was like new when I went to read the plugs.
When doing a static spark check, all were firing...why...because the ignition system was in QS mode while doing the spark check test. Then, sure enough after I saw #2 plug was like new, I actually started it up with a timing light on #2, and watched the spark drop exactly when QS disengaged. Very weird.

The key here is the fact you have lost 1000 rpms. Almost always a sign in a v6 that one cylinder is down.
 
yes. do the testing to be sure you are dropping a cyl first tho.
read exactly what i did above to arrive at the dropping cylinder conclusion.

there are 6 787071 manuals on ebay right now.
 
daselbee said:
<...> Then, sure enough after I saw #2 plug was like new, I actually started it up with a timing light on #2, and watched the spark drop exactly when QS disengaged. Very weird.

The key here is the fact you have lost 1000 rpms. Almost always a sign in a v6 that one cylinder is down.
Click to expand...
Just an aside on reading Sparkplug's, any trace of water in combustion chamber (Gasket, Crack or Hole) will really Clean that sparkplug.

Newly installed plug "like new" after run told you what you needed for sure.:cool:
Art
 
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