'90 johnson 40 will not stay running

[mrolp84]

hey all,
i have a 1990 johnson 40 hp vro outboard. Sunday i took it out and it ran great have not had a problem until now. i was heading to the dock at about 3/4 throttle when i lost my hat, i throttled down , spun the boat around, got the hat at idle, then proceeded to throttle up to get back on plane. I reached my cruising speed when the motor slowed down in rpms and when i brought the controls to netrual it died. I thought i ran out of fuel but when i hooked up a second tank that was full and when primed up it would not start. i had to push in the ele. primer to get it to start and then had to keep pushing it to keep the motor running. when i got home i changed the plugs, fuel filter and even got fresh gas. i pulled the carbs and cleaned them. compression on each cylinder was at 120/125 out of three test on each cylinder. i checked for spark with a spark tester and both are firing. I got it to start and tried to adjust the carbs. It seems to favor the top clyinder cause no adjustment to the bottom carb made a difference. When it warmed up it quit just like before. Again i could get it to run and stay running with the primer but once i stopped pushing the primer it would stop. I am lost any help would be great. i am a mechanic (small engine) so nothing is too much for me. I just need another set of eyes so to speak. i also did a link and sync since i removed the carbs. If more info is needed just ask and thanks again for your time. -matt o.

 

[bktheking]

Re: '90 johnson 40 will not stay running

How long did it run for before it died, when you got it running and started adj the carbs?

 

[mrolp84]

Re: '90 johnson 40 will not stay running

maybe 15 min just at idle i just adjusted the carbs to keep it running it sounded normal but than just shut off and would not re-start. i am also getting good fuel flow out of the vro i disconnected and tested for flow. i kept the spark tester hooked up and i don't think i lost spark

 

[bktheking]

Re: '90 johnson 40 will not stay running

So after it dies and you try to restart it you do have spark?

 

[mrolp84]

Re: '90 johnson 40 will not stay running

yup got spark i even did a compression test when warm and got the same results. if i push the primer in it will start and if i bump the primer it will stay running but quit if not pushed every ten seconds. would a bad power pack light up a tester but still be to weak to fire a plug? also why does it favor the top cylinder is this normal in these engines? thanks, i can't sleep fall striper season is coming.

 

[bktheking]

Re: '90 johnson 40 will not stay running

No doubt, I couldn't sleep either. A bad powerpack and there is no spark and you say you are getting spark. I did have a 9.9 in last week that had spark that came and left, one of the wires coming out of the pp was shorting inside of the powerpack, one minute you got spark the next you didn't but it was noticeable. Once I replaced the pack the motor ran forever, the owner put 10hrs last week and it didn''t miss a beat. Bumping the primer richens the mixture, normally when you bump the primer the thing will buck and blow more smoke and possibly die. Yours is running normal with choke closed, being a small engine mech and that's where I started, running only on choke means the motor isn't providing the proper fuel air mixture to run the motor.Sounds like a fuel problem. You said you cleaned the carbs, I noticed that these carbs have an idle mixture screw, did you pull the screw, clean the crap out with cleaner and hit it with compressed air?

 

[mrolp84]

Re: '90 johnson 40 will not stay running

yes i tore down the carbs bare put them in a hot bath that uses hot soapy water instead of harsh chemicals. i then sprayed the carbs with crc carb cleaner and compressed air. i think i may need kits have never really "rebuilt" the carbs just cleaned them since purchase last year. i don't like the looks of the welch plugs and the o-rings around the air/fuel adjust screws. i just don't understand why it quits when warm. i am going to test the power pack via selocs manual spec and see what then. i am also going to tear down the carbs again just in case i pulled trash when changing filters. i hope it is just a fuel problem i think i may replace all hoses as well just to get closer. thanks BK P.S. don't let me keep you up. -matt

 

[tashasdaddy]

Re: '90 johnson 40 will not stay running

possible ethanol poisioning. read here, http://forums.iboats.com/showthread.php?t=299680

 

[mrolp84]

Re: '90 johnson 40 will not stay running

thats the plan to replace the fuel lines and clean the carbs again. i hope this is just a fuel problem though. any complaints about the sierra rebuild kits? i would like to purchase from this site and i don't see an omc kit. i just like to use factory stuff but if the sierra is just as good i will try them.

 

[tashasdaddy]

Re: '90 johnson 40 will not stay running

i use sierra all the time.

 

[mrolp84]

Re: '90 johnson 40 will not stay running

okay got back to the motor today. i replaced all of the fuel and oil lines as well as carb gaskets. i cleaned the carbs again and got fresh fuel. after getting her to start and idle i let it warm up and it seemed to run okay. made some more fine tune adjustments and from what i can tell i seems to be doing okay. i am still going to buy rebuild kits i think they may give me an even smoother idle. my theory was i had bad fuel. when i sat down and thought about it i had filled up that morning but did not use that tank until it was time to go in. the trip from the cove to the dock is about 5 miles and about half way though is when it started to slow down an then die. so i feel bad fuel was to blame. now here is a question, do these stacked two cylinder engines favor the top cylinder? this one seems to be more picky to adjustments made to the top carb than to the bottom. most two cylinders i work on are v-twin or opposed twin. this style motor is new to me but i really do like them. thanks for your help guys and i will let you know how my first trip out goes later this week. thanks again -matt

 

[SparkieBoat]

Re: '90 johnson 40 will not stay running

did you try throwing your hat back into the water??? LOL
I couldnt resist. I hope your problem is resolved.
good Luck Sparkie

 

[mrolp84]

Re: '90 johnson 40 will not stay running

you know i thought about throwing the hat back in but i dont think i need to replicate every step to make sure i got it right! lol thanks on another note does anyone have a tach hooked up to this size motor i want to install one and want to know how to hook it up?