15hp Johnson Won't run more than 15-20 seconds

[tjpowell453]

Hi there. This 1985 Johnson 15 hp motor will kick over on the first pull everytime and sounds strong for about 20 seconds then sputters and dies. I cleaned out the fuel pump and checked it - it squirts when the rope is pulled...<br /><br />Pumping the bulb doesn't help. The only way I can get it to run at all is full choke. Playing with the throttle and choke will by me a couple more seconds of run time. <br /><br />Waiting a few seconds and then re-pumping the fuel bulb will get it going, and then die again. Any ideas? <br /><br />The motor sat up for a long time apparently, but looks to be in A-1 prime condition otherwise.<br /><br />I have not rebuilt or removed the carb. Float problem maybe?<br /><br />And yes BTW, I am using new fuel @ 50:1 and vent is open !<br /><br />Thanks!

 

[snapperbait]

Re: 15hp Johnson Won't run more than 15-20 seconds

Sounds like the float or needle sticking in the seat..

 

[jessieb]

Re: 15hp Johnson Won't run more than 15-20 seconds

i would take the carb off and soak it in some carb cleaner and make sure you get all the trash and gummy stuffy out of it and reset the float and this should fix the problem, if it don't it might be a timing problem but i would start with the carb.

 

[tjpowell453]

Re: 15hp Johnson Won't run more than 15-20 seconds

Yep. I think that is the right next move. Starving for fuel, with maybe a slow trickle re-filling the bowl... I will rebuild the carb, then post the results.<br /><br />Thanks very much guys. I appreciate it.

 

[Jack Shellac]

Re: 15hp Johnson Won't run more than 15-20 seconds

I have an '84 Johnson 15 and agree that the carb is probably your problem, with the most likely being a sticking float needle. Try this just as a test; Tap the carb bowl lightly with a plastic screwdriver handle and this will frequently free up the needle. I think I would still go with a carb rebuild though, even if it runs after this.

 

[maked]

Re: 15hp Johnson Won't run more than 15-20 seconds

hi I just want to put in 2cents, I borrowed off someone else on this forum, first, I absolutely agree with everyone else on this post, clean check adjust carb, its most probably in there. In the very unlikely event that that doesn't solve anything, have the reedvalves checked, I know is sounds strange but they can apparrently stiffen up making it difficult for the engine to get enough fuel to burn, which means heavy choking is needed and creates its own associated problems.<br />have fun

 

[tjpowell453]

Re: 15hp Johnson Won't run more than 15-20 seconds

I took apart the carb last night and sure enough, it was full of crud, bowl varnish and the jets were thoroughly clogged. Looked like the needle valve was free however. I think the main jet being as crudy as it was might cause this to happen.<br /><br />I will have the rebuild kit in later this week, and will post more then. Thanks again for the very helpful advice!