1994 Johnson 25hp Missing at mid throttle

3

3with1shot

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Mar 16, 2010
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Compression checked out to 105 and 115. Carb has been cleaned 3 times, replaced high speed jet. cleaned fuel pump, new champion plugs, replaced 1 coil, new gas tank, new line, and new bulb. Starts great and runs fine until it gets to mid throttle and acts like it is starving for gas..bulb does not stay hard..I can pump bulb while running and it gets hard and then goes down? Running out of ideas??? Power head?
 
A

AlTn

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Mar 9, 2010
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Re: 1994 Johnson 25hp Missing at mid throttle

put some fuel mix in a spray bottle and spray it in the carb throat when you reach the "starving for fuel" point..if the motor picks up ...you've got a fuel delivery problem...if it floods..you've got an ignition problem...the bulb becoming soft is normal, as it becomes part of the fuel line , so to speak, after the motor runs for a while
 
jasper60103

jasper60103

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Re: 1994 Johnson 25hp Missing at mid throttle

3with1shot,
I was thinking when you mentioned things start acting up around mid throttle (i.e. starving for gas), maybe you can see a change in fuel delivery?

I don't know the answer, but when I ran my motor with the hood off, I could see a lot of fuel spitting down the carb throat when throttled up, around the 2:20 or so (see video below). Also, you can observe the position of your butterfly. I'm thinking when things start acting funky, maybe you'll see the fuel delivery interrupted, or something strange going on? I'm no expert though.

http://www.youtube.com/watch?v=wd5TOTrxFSs

edit: I guess my reasoning is similar to AlTn above.
 
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3with1shot

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Mar 16, 2010
Messages
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Re: 1994 Johnson 25hp Missing at mid throttle

Thanks guys. Is there a way to test voltage coming out of coils? I can see an arc across both plugs. will try spraying gas in carb this weekend.
 
jasper60103

jasper60103

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Re: 1994 Johnson 25hp Missing at mid throttle

3with1shot said:
Thanks guys. Is there a way to test voltage coming out of coils? I can see an arc across both plugs. will try spraying gas in carb this weekend.
Click to expand...

Buy yourself a spark tester for about $6-7 at an auto parts store. A strong blue spark should jump 1/2" air gap, then call it good.

You can also go to the CDI website and checkout their troubleshooting guide...http://www.cdielectronics.com/Support.aspx
 
Cofe

Cofe

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Apr 23, 2009
Messages
1,883
Re: 1994 Johnson 25hp Missing at mid throttle

Check fuel pick up line in the fuel tank, some have screens that need cleaned once in awhile. Check all fuel lines for good tight connections and check the o-ring in the fuel line quick disconnect on the motor. Feel fuel lines for exterior vibration rubbs, these can let air into the fuel line. Kinked lines are bad also.
If you can borrow a fuel tank from someone, you could quickly find out if yours is bad. Hope this helps
 
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3with1shot

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Mar 16, 2010
Messages
9
Re: 1994 Johnson 25hp Missing at mid throttle

Thanks for the help guys. Definatley have fuel delivery issue. sprayed gas in carb and no missing. anybody ever added a in line 12V fuel pump?
 
jasper60103

jasper60103

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Messages
2,055
Re: 1994 Johnson 25hp Missing at mid throttle

3with1shot said:
Thanks for the help guys. Definatley have fuel delivery issue. sprayed gas in carb and no missing. anybody ever added a in line 12V fuel pump?
Click to expand...

If you suspect your fuel pump is the problem. I would try pumping the bulb when it's starving for gas and see if that makes a difference.
 
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