Johnson 25hp 1979 starting and running problems.

[sxm_tj]

Hello,

I have a johnson 25 hp outboard engine from 1979 with an electronic egnition and electric start.

the problem:
it first started like this :
engine ran fine but at low rpms the engine sometimes stutered.
then sometimes at high rpms the engine would got down to lower rpms, as if she was running on 1 cilinder.

no she doesnt want to run longer than 5 seconds.
she starts and then bam shuts off again and a "ploff" from the carb and gas sprays out the carb.

ive cleaned the whole carb, ive check the spark, ive tested the coils,they all work fine, i have got no clue whats wrong with it, i am a car mechanic but this beats me.

could it be a default powerpack, or a default head gasket, what could it be, please help.

thanks



could it be that the powerpack some how fails or that the

 

[bgbass.1]

Re: Johnson 25hp 1979 starting and running problems.

sound like carb. problem try adjusting float sound like flooding.

 

[tashasdaddy]

Re: Johnson 25hp 1979 starting and running problems.

check the fly wheel key, if sheared, will throw timing off. do you have good bright blue spark. also read this. http://forums.iboats.com/showthread.php?t=158071

 

[sxm_tj]

Re: Johnson 25hp 1979 starting and running problems.

check the fly wheel key, if sheared, will throw timing off. do you have good bright blue spark. also read this. http://forums.iboats.com/showthread.php?t=158071

i just renewd the key so thats no the problem, and the carb is not flooding, i tetsted that, anyone else idea's or had this problem before?

 

[tashasdaddy]

Re: Johnson 25hp 1979 starting and running problems.

link n sinc? gas spraying out the carbs, tells the the reed valves are a problem. they are behind the carbs, and have to be totally clean, straight, not bent. what's your compression?

 

[sxm_tj]

Re: Johnson 25hp 1979 starting and running problems.

Wel i checked the reedvalves visually when i took the carb off, they looked very nice and clean and not worn out, but il inspect that beter to be sure, compression is good but ill try to get a compresion tester from work to see what the graphs say.

is this a possible problem or is there no high spoeed ajuster, and the lowspeed ajuster could also be wrong.


(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

 

[catfish hunter]

Re: Johnson 25hp 1979 starting and running problems.

I have the same problem with mine. Its a 1981. I thought it was the carb but I have rebuilt it twice now. Good spark and compression. Checked the plugs and there wet. Im lost. Its getting ready to go to the shop. I just dont want to see the bill If I find out anything ill let you know.

 

[sxm_tj]

Re: Johnson 25hp 1979 starting and running problems.

I have the same problem with mine. Its a 1981. I thought it was the carb but I have rebuilt it twice now. Good spark and compression. Checked the plugs and there wet. Im lost. Its getting ready to go to the shop. I just dont want to see the bill If I find out anything ill let you know.

googluck hope they find it and its not too expensive

 

[sxm_tj]

Re: Johnson 25hp 1979 starting and running problems.

oke i im going to clean the carb trugly tomorrow at work, now i want to do a link an sinc, but how i have no acces to a book.
ive read lots of treads but cant really find any info on how to do this or just give me an idea of how to do this.