J3BRCEC 1989 Johnson 3HP dies on quick throttle

Hello all!

I'm at my wits end with this motor and thought I would appeal to you guys for some help. I've tried searching for issues similar to mine but other motors seems to be more complex than what I'm dealing with. Mine doesn't have a fuel pump, primer bulb or anything like that.

So my troubles started when I got water in the motor via bad gas. Since then I've cleaned/dried the carburetor completely/rebuilt it. I replaced the spark plugs and dried out the pistons. I also dried out the gas tank and gas line. Put new gas in and everything runs fine. It starts on the first pull and idles without issue. However when I increase the throttle gradually it'll start to stumble at about 2/3's, if I do it fast it'll die. After stumbling a bit sometimes it'll die or get itself right and kick out a bunch of exhaust and then it'll run full speed for as long as you please. It'll even throttle down to idle fine, but if you kick it back up it'll stumble again.

Seems to me it's running rich and having trouble burning all the gas it's getting hence the plume of exhaust it kicks out right before it starts running fine. Just a guess, but I really don't know what else to look at. If anyone has any troubleshooting tips or things to check I'm all ears. Is there a surefire way to tell if its rich or lean? Can I use the choke to see if it's lean or blow in the air intake to see if it's rich?

Also, it's an old motor but compression is 90 PSI in both pistons. I've also hooked up a spark tester and tested both plugs, they seem to both be running fine.

Sorry for the long post, I like to let you in on all the details!

Thank you for any help!

Eric

Re: J3BRCEC 1989 Johnson 3HP dies on quick throttle

Sounds like you still have a carb problem. When you cleaned the carb did you just take the bowel off or did you actually overhaul it?
Are the high and low speed needles set properly?

Re: J3BRCEC 1989 Johnson 3HP dies on quick throttle

Daviet said:

Sounds like you still have a carb problem. When you cleaned the carb did you just take the bowel off or did you actually overhaul it?
Are the high and low speed needles set properly?

Click to expand...

Well I bought a rebuild kit and took it apart enough to use all the parts in that. I've sprayed all the holes with carb cleaner, I even popped the aluminum cap and sprayed the idle jets and used a flashlight to verify the holes we're clean. My carb doesn't have adjustments for a high speed needle so nothing to adjust there. It just has an idle screw which is turned 1 1/2 out from seated. I must not have something right, I've triple checked the float as that's where I think the problem might be but I can't see anything wrong with it, its level with the carb when inverted and I can hear it move around once I have it back together.

Thanks for the reply, I'll go back in and see if I missed anything.

Re: J3BRCEC 1989 Johnson 3HP dies on quick throttle

OK well I've gone back in the Carb a few times and haven't found anything new. I've run wire through all the jets and sprayed them, its pretty clean in there. I did notice that my fuel line when disconnected seems to dump gas out pretty quickly. It does this even when the tank vent is closed. Shouldn't it be held back by vacuum? It goes right from the tank to the Carb and I don't see any gas leaks. Also I've noticed when throttling down to idle from 2/3rds throttle it'll sometimes die. It'll start right back up tho and idle forever. So it seems to have trouble throttling up or down quickly, but only 70% of the time.

Re: J3BRCEC 1989 Johnson 3HP dies on quick throttle

So an update on this situation, I've taken it out on the lake for the first time since troubleshooting. It started out just fine, started right up and changed throttle positions without issue. However after about 50min it started having trouble, you could hear it stumble slightly, then it didn't want to go past 1/2 way, every time I tried to do it it started to die. It was very consistent like this until I tried pumping the choke. After that it perked right up and was fine for the next 1-2 hours and didn't have anymore issues for the rest of the day. So it seems I have a lean condition that shows itself when it wants to. I'll update this post if I find anything else out.

Re: J3BRCEC 1989 Johnson 3HP dies on quick throttle

Hi there!

I've the same motor with the same problem. We're you able to get it running right in the meantime?