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1989 Johnson 70hp SLOW mode

C

cdodge1983

New member
Hello,
I have a 1989 70hp Johnson. Every time we get up to 20mph the boat goes into slow mode. You could literally just put it in water and hit throttle and as soon as you get that fast, boom slow mode. Steps taken so far.
1. Unplugged temp switch and still does it.
2. Replaced thermostat
3. Tested voltage and found bad rectifier. Replaced with new. Voltage now stays between 12.6 and 13.4
4. Replaced power pack
5. replaced all electrical cables to control box and put new control box in. More because old one was broke and such.
6. Replaced impeller and inspected all areas for clogs
So someone mentioned possible stator however now we are getting into the guessing game. I am not throwing more money at it unless i know.
Any thoughts on Stator or something else i can check. Otherwise getting to point to find someone reliable to bring it to.
Thanks
 
I can not see or hear your motor.----Information is needed.----Compression test must be done.---Post the numbers.----Does spark jump a gap of 3/8" or more on a test device?----Does tell tale come off the side of the block or the top of the block ?---Any other trouble shooting done ?
 
Last edited:
racerone said:
I can not see or hear your motor.----Information is needed.----Compression test must be done.---Post the numbers.----Does spark jump a gap of 3/8" or more on a test device?----Does tell tale come off the side of the block or the top of the block ?---Any other trouble shooting done ?
Click to expand...

Racerone
compression = 120 each for all three
spark plug gap = .03 each plug
tale comes off top of block and is steady stream

Disconnect thermal and still does it, dont think overheating as temp does not get that hot right away when it goes into slow mode.
 
Sorry----I asked whether the spark can jump a gap of 3/8" or better.---I did not ask what the plug gap is on your motor !
 
Check the flywheel key.-----A sheared key throws off the timing.----Run with a timing light one cylinder at a time and observe flashing light as you hit the 20 MPH mark.------And remove intake silencer cover.----Use a STRONG flashlight and observe / compare fuel amount coming up the main nozzles.------Note----No money spent doing these simple tests.-----
 
racerone said:
Check the flywheel key.-----A sheared key throws off the timing.----Run with a timing light one cylinder at a time and observe flashing light as you hit the 20 MPH mark.------And remove intake silencer cover.----Use a STRONG flashlight and observe / compare fuel amount coming up the main nozzles.------Note----No money spent doing these simple tests.-----
Click to expand...
Thank you for the feedback, greatly appreciated will try this out and see what i get
 
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