70 hp johnson stumbles

[barroomhero]

Working on a 70 hp johnson that idles and runs fine out of the water but as soon as it goes in the water it stumbles and will not idle with no power..... Any ideas? I'm thinking the carbs need to be adjusted in the water due to influence of backpressure...... timing? Any suggestions would be great, Thanks

 

[fireman57]

Re: 70 hp johnson stumbles

You are correct. You need to set your idle while the boat is in the water due to the backpressure. Try that then post back your results.

 

[Randybeall]

Re: 70 hp johnson stumbles

I had that problem. Regapping the spark plugs to .040" solved the problem. Champion chart showed .030" which was wrong. I had a hard time believing the change.

 

[tx1961whaler]

Re: 70 hp johnson stumbles

Where did the .040" gap specification come from? I haven't run across any Johnson/Evinrude that specs out a .040 gap........

http://www.boatsetup.com/SparkPlugChart.pdf

 

[DJ]

Re: 70 hp johnson stumbles

That .040" gap has come from years of experimentation by many boat owners. It does make a difference, especially at idle.

You are not getting full power from all three cylinders. It is the first sign of carb. troubles: dirty, misadjusted, etc.

 

[barroomhero]

Re: 70 hp johnson stumbles

I gaped the plugs to .040" and still had to luck. I do not have much experience with these older carbs, I was looking to fine tune the air/fuel mix. Where are the screws? Put the boat in the water and it starts hard.....once running it will not idle and when you try to accelerate it bogs down, like its getting to much fuel. Then we you try to start it, fuel pours out of the carb.... Improper float height? Cylinder one was not spraying fuel when I cranked it over with the plug out. Any ideas? The model number is J60ELCDS and serial is J7122208


Thanks

 

[barroomhero]

Re: 70 hp johnson stumbles

Took apart carbs and found small debris but nothing extreme. I found a bent elmusion tube, is this normal?

 

[barroomhero]

Re: 70 hp johnson stumbles

Any chance it would just be clogged jets?

 

[barroomhero]

Re: 70 hp johnson stumbles

What should the proper float height be?

 

[barroomhero]

Re: 70 hp johnson stumbles

Cleaned all three carbs, inspected fuel pump and check all fuel lines. Cylinders one and two are not getting fuel and I can't figure out why. 120, 110, 120 psi for compression respectively. Any ideas?

 

[barroomhero]

Re: 70 hp johnson stumbles

So I took the plugs out and cylinder 3 is getting plenty of fuel but not 1 or 2. I switched carb 3 with one to see if the issue was with the carb and 3 is still putting out good fuel with carb 1. So I am now wondering if it could be the reeds. 1 and 2 spit fuel out the carb when cranking, could the reeds not be closing properly. Any ideas on the specs for the reeds

 

[barroomhero]

Re: 70 hp johnson stumbles

Reeds are good, float height is good, no matter what i do #3 has fuel and the other two do not.

 

[fireman57]

Re: 70 hp johnson stumbles

Wow, this thread went from setting your idle to no fuel. What a quirky turn of events. I also see that you started a new thread. It's tough for someone to follow if you do that and the people that are trying to help you get confused. If you are sure that this is the problem then you might ask the mods to get rid of this thread.