25 hp johnson running bad PLEASE HELP!

jigemup

Cadet
Joined
Mar 29, 2011
Messages
19
I have a 1976 Johnson 25 HP manual start that started running bad saturday while fishing. When I start it acts like it wants to die. Then when I can keep it running and go to shift into gear it acts like it wants to die. When I was finely able to get it into gear, I would have to give it alot of throttle in order for it to keep running. At all speeds it just seemed doggy and acted like it was going to die. Not a mechanic so any help would be great

THANKS
 

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: 25 hp johnson running bad PLEASE HELP!

Probably running on 1 cyl. Do a compression test and hook up a spark tester and check for spark on both cylinders.
 

jigemup

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Joined
Mar 29, 2011
Messages
19
Re: 25 hp johnson running bad PLEASE HELP!

So I did a comp test and ea h cykinder is at 120lbs. I have the motor in a tank now and it starts on the first pull. As it sits there idling it is rough. As soon as I try to move the throttle to the shift position it dies. But if I mess w the choke and idle it up it will run as long as soon as I try to slow the motor down it dies?
 

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: 25 hp johnson running bad PLEASE HELP!

Perhaps you should try to clean/rebuild the carb as first option. However check that you are not loosing spark as you start advancing the timing.
 

jigemup

Cadet
Joined
Mar 29, 2011
Messages
19
Re: 25 hp johnson running bad PLEASE HELP!

Where do I get a service manual as I'm unsure about tearing into it with out the proper knowledge?
 

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: 25 hp johnson running bad PLEASE HELP!

Try to get an OEM manual:
e-Bay
Marineengine
Ken Cook
 
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