79 johnson 9.9 dies at full throttle

[brokenjohnson9.9]

three years ago I was given a 79 9.9 johnson short shaft, manual start, outboard by my father who had it since new. It had sat around for a few years but ran well over all. now its thing is at full throttle it will run for twenty minutes or so and then rpms and power will fall off. If I apply full choke it will run at half speed(still full throttle) and really lug. If I try to open the choke it will stall. It appears to run allright if I stay at 2/3 throttle or less.<br /><br />I have replaced the fuel line and tank. Had the lower end re-done with new impeller and thermostat.<br /><br />If I squeeze the primer bulb during the low rpm condition, no change is seen. Vent is open on tank<br /><br />Tiller grears are in sync and not off a tooth<br /><br />After each stalling it getts harder and harder to start. it acts like its flooded (full throttle open choke 15-20 pulls to get a stammer then 5 -10 more to start it)<br /><br />I plan a carb and fuel pump rebuild but would like other possible solutions in case that fails.<br /><br />Thanks in advance,<br />Charlie

 

[fireman57]

Re: 79 johnson 9.9 dies at full throttle

At first glance it seems like you may be losing fire. Make sure that you don't have a coil overheating and dropping a cylinder. You say that it will run okay at 2/3 throttle. That indicates more of a fuel problem. Could have some junk in the carb. Buy a rebuild kit and do them like you say. make sure that you blow all the orafices out with a good carb cleaner and compressed air. Give them an overnight soak if you can. You shouldn't have to be full throttle to start this baby. I have a '76 9.9 that I love and it starts second or third pull.

 

[ezeke]

Re: 79 johnson 9.9 dies at full throttle

Just one person's opinion, but it is a waste of your good time rebuilding that fuel pump - just get a new one. <br /><br />Spend your time on the carburetor, where it counts.

 

[brokenjohnson9.9]

Re: 79 johnson 9.9 dies at full throttle

Thanks guys for your response. It may be a week or so until I get a chance to get the parts together and see what was what. <br /><br />I took the carb apart and the bowl had a fine rusty looking grit to it, that was also on the main jet. and some whiteish scale all gone now and its soaking now.<br /><br />Inside that main jet that goes through the float<br />Is that included in a rebuild kit or should I try to remove that and claen it out or just blow it clear. I hesitate because it looks like the wrong size driver was used and the slots are rounded and might be problematic to getout without killing something else.<br /><br />I guess the next question is how would I check to see if the coil is overheating and dropping out? remove the plugs and do a spark test on the water once the problem happens?<br /><br />I will get a new fuel pump and save myself that fun (thanks for that suggestion)<br /><br />Hope to have this running soon, I need some reliable relaxation.

 

[OBJ]

Re: 79 johnson 9.9 dies at full throttle

No you don't have to pull the main jet. Just get a can of choke and carb cleaner and shoot the stuff through the jet hole. Won't hurt to shoot it any place else you can find a hole either...... <br /><br />If you get an OEM kit, which I suggest cause you get a new float and new core plugs, knock out the core plugs and shoot them also. The large plug on top of the carb covers the idle holes. I would at least knock this one out and make sure there is nothing laying in there.<br /><br />I wouldn't worry about the coil till you get the carb done and pump on and see what she's going to do. Take it one step at a time. And yeah....I agree with ezeke....just get the pump. OEM kits come with instructions but I've seen a lot of guys still bring them back put together wrong.<br /><br />EDIT: Forgot to mention....once the carb is soaked and blown out with carb cleaner....follow all this up with compressed air. This usually dislodges anything still sticking around.

 

[jleus]

Re: 79 johnson 9.9 dies at full throttle

One thing often overlooked is where the trash in the carb(s) is coming from. Be as thorough with cleaning the tank as you are with the carb or you will repeat.