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1984 25hp not running right

E

Ervin Brumfield

New member
My 1984 25hp johnson has always ran like a sewing machine til one night I went fishing and it wouldn't start. Since I have rebuilt the fuel pump, new fuel lines, new plugs, rebuilt the carb and instaled a new water pump. The motor will crank it just idles riff and will not run at full throttle when in the water in gear. I try the motor at the house and it seems alright but when the motor has a strain on it it will not come up to speed hoses you hand choke the carb what's wrong
 
Hook up a spark tester at BOTH cyl's.
Unscrew the plugs, pull the cord.
Sparks should go 1-2-1-2......
My guess you have either a dead cyl, or a cyl that double fires. (2 cyl's at the same time)
If so, change the power pack.
At the same time do a compression test, both cyl's within 10% of each other.
If you do not have a tester, make one:
 

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sounds a LOT like what i'm going thru with my 1981 evinrude 25hp. see the thread titled "sometimes it starts, sometimes it doesn't" down the list a bit. i am going to update that thread today after i fiddle with the boat again in the driveway.

good luck- you've done a lot of work on your engine.
 
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