1990 70HP Johnson started for the first time in 20 years, Idle problem

[soundchaser]

Hello Let me say first, Any help here is greatly appreciated.......) Okay here's my story, I bought this Motor probably 15yrs ago and had it sitting in front of my garage on a stand since then and it had sat for at least 5 before that. I always had a feeling it was a low hr motor. So I just kept it around incase there came a day that I wanted to employee it... Well That day has come, I picked up a 16' Wahoo boat and I'd like to run the motor on this boat.

Here's what I've done so Far, I obviously went to cleaning it, But far as mechanical, I removed the complete fuel system and cleaned the Carbs real clean. It was a VRO, so I replaced all the fuel lines, Mounted the fuel Pump, Made a new brass fuel bar manifold. got everything to a point I thought would be a go.... Problem I'm having is I can get the engine to start at too high RPM's but it doesn't want to idle down. It just shuts down. I do have a thick mix of oil in the Fuel, but I did put fresh plugs in it too. After starting and running a little bit, I did a compression check and all cylinders came up at even and just over 120psi

One Question I have is,
I see there's a fuel/air low speed adjustment screw on each carb, what's the average turns out these motors like to idle at?
I looked at the plugs after I checked for spark and ran it, one was wet, One was black and one looked good and tan... Should I consider going back after cleaning the carbs or might I just have the air/fuel screws wrong at one turn out?
I also have removed the drain plugs from the carbs and Hand pumped fuel Through the carbs. Everything seems even and after I ran the Engine, The manual ball is still hard, I suspect the fuel pump is working fine...
Any other ideas about my problem are welcome... Again Thanks for any help in avance... Harry

P.S. I have pics, But it's not letting me post them

 

[JerEazy]

1 1/2 turns is the general setting on the idle screws.

Then start at the top and work your way down 1/4 turn out at a time - wait a few seconds to let it take and see if it changes sound. Keep doing that until it loads up. Then go the other way doing the same thing until you hear it start to sputter from being lean. Setting is in the middle. Do that all the way down, and then I do the top again. But that may not be necessary.

 

[jakedaawg]

Probably best to check for spark on all 3 leads 1st.

I find its easiest to do these in the water, the final adjustments. You can get it relatively close in a big barrel but on muffs tuning tends to be useless...

 

[jakedaawg]

Also,.verify that red lever on primer solenoid is in line with solenoid body, not 90 degrees.

 

[IDFISHER]

Maybe it's just a typo but I dont believe the VRO was in existence in 1970.

 

[jakedaawg]

Maybe it's just a typo but I dont believe the VRO was in existence in 1970.

I believe it's a '90 70hp...

 

[IDFISHER]

I believe it's a '90 70hp...

Sure enough, my mistake. Clearly not enough coffee in my system today.

 

[oldboat1]

I do have a thick mix of oil in the Fuel

What does this mean?

 

[soundchaser]

I added extra oil for initial start, But now I have a regular 50:1 mix in it. Where I'm at now Is I have the carbs perfectly clean and when I check spark it seems to be fine. But the engine still will not idle correctly. it's bucking and jumping..

 

[jakedaawg]

On muffs or in water?

 

[Crosbyman]

have you tried fuel type products like BRP decarb or Seafoam… ….. some like it some don't

mix up 1 gallon 50/1 oil and add half a can of Seafoam

start her up and let it circulate the juice … it will smoke

 

[oldboat1]

If your model has a needle valve angling out from the carb top, that's an idle adjustment for the air/fuel mix. Close it (them) gently clockwise until they seat, then back out c.clockwise about 3 turns. See if it starts and runs at that setting, If so, let it warm up and adjust clockwise (leaner -- more air than fuel) about 1/8 turn and let the engine adjust. Do the same with the other carbs, then return and work through again. At some point the engine will pop (lean sneeze) or stall. At that point, open the needle(s) about 1/4 turn and try running with that.

If you have a service manual, look for the initial needle setting and use that -- if it's something other than three turns. Older motors used 1 1/2 turns as the standard initial setting.

You need to do this in the lake or with the l.u. immersed deep in a large barrel or trashcan (water about half way up the leg). Hopefully, you will see less bucking and jumping after adjusting. Idle or fast idle only if running in a barrel -- avoid flushers as you need some back pressure to make the adjustments.

 

[soundchaser]

Well here you have it, I pulled the flywheel and found a sheered timing key. Hopefully if this engine didn’t go through too much of a hard time, it’ll be ok... I’ll try running it tomorrow when I can pick up a new key... I’ll keep you posted.... thank you very much for the help so far......)

 

[soundchaser]

By the way, as hard as it was to pull that flywheel, I kinda knew that key was sheered and wedged.......