| Author |
Message |
    
phillip ramsey
New member
Username: phillipramsey
Post Number: 1
Registered: 07-2009
| | Posted on Thursday, July 02, 2009 - 12:35 am: | 
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the motor starts and runs fine but when i open it up to full throttle it starts to take off and then shuts down to about half power. it will jump to full power every once in a while and sometimes when it does this it will stay at full power until you throttle it back down. i have replaced the coils, points, and condensers and im not sure what else to do? |
Bob Caskey
Advanced Member
Username: bobbyc
Post Number: 415
Registered: 10-2007
| | Posted on Thursday, July 02, 2009 - 06:18 am: |
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Sounds like one of the cylinders is not firing under certain conditions. When it goes to half power, let it run for a few minutes and then feel the temperature of each cylinder head. The non firing cylinder should be noticeably cooler. If that is the case, then check that cylinder for spark. Usually an ignition problem but several other possibilities. One on the water test would be to temporarily gap the plug to about .010. If the cause is a weak spark, this will put less demand on the system and if the motor then runs normally, you have found the problem. |
dan
New member
Username: dntrylr
Post Number: 1
Registered: 07-2009
| | Posted on Saturday, July 04, 2009 - 09:19 am: |
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1975 70hp johnson have only half power at full throttle been running great put up for winter took out and now just half power something sticking? |
Morten Ringvold
Senior Member
Username: haffiman37
Post Number: 3886
Registered: 04-2006
| | Posted on Saturday, July 04, 2009 - 09:31 am: |
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Dan.
More likely a clogged main jet in one of the carbs. |
dan
New member
Username: dntrylr
Post Number: 2
Registered: 07-2009
| | Posted on Saturday, July 04, 2009 - 09:39 am: |
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do i need to take apart or can I spray cleaner in carb? |
Joe Reeves
Senior Member
Username: joereeves
Post Number: 7581
Registered: 02-2001
| | Posted on Saturday, July 04, 2009 - 09:45 am: |
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Take it apart, clean and rebuild it.
Spraying cleaner into a carb is a waste of time. It simply goes thru the carb throat and into the crankcase..... not into the carburetor passageways.
Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:
http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store |
Morten Ringvold
Senior Member
Username: haffiman37
Post Number: 3887
Registered: 04-2006
| | Posted on Saturday, July 04, 2009 - 10:01 am: |
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You may get away by taking out the drain plug in the float bowl and then with a screwdriver remove the main jet, but the best and safest it what Joe describes. Following Joes's advice You need the repair kit at hand. My suggestion is more a 'band aid' attempt. |
