73 Johnson 9.5 rough idle

[cr9c1]

My 73 Johnson 9.5 (Some of you may have seen/heard about already) has a rough idle problem.

The following things/parts have been replaced:

Coils, Points, Condensers, Spark Plug Wires, Spark plugs

I have rebuilt the carb with the carb kit from OMC including all new float, needle valve, seat, all applicable o-rings, washers, removed both core plugs and checked for gunk (Found none)

I also cleaned the flow bowl and everything I could get at on the carb system. I soaked the carb in carb cleaner and blew it out with compressed air. Only thing I saw when disassembling was some varnish in some of the passageways of the carb and the float bowl.

It'll idle right down and everything fine, and I've checked my mixture screw 4 times to make sure its set where it should be (Per Joe Reeves article)

It runs rough low speed only, high speed seems ok, and though I haven't had the time to take it to the lake (It was near dark when I finished rebuilding the carb, and trying to rebuild the steering tensioner thing) it did run rough at the lake on the boat before the carb rebuild and has run rough since after it.


My second question is: I disassembled all parts that tighten the steering up and verified according to the diagrams on Evinrude's website that the parts are all there. It just doesn't seem to tighten up. The threads of the bolt look fine, as do the threads on the square nut that sits down inside the stern bracket.

All help is greatly appreciated. (I have also verified that all three small holes in the throat of the carb flow freely, as this was the reason my last 9.5 wouldn't idle at all)

 

[samo_ott]

Re: 73 Johnson 9.5 rough idle

Maybe you have a vacuum/intake manifold leak? If air is getting in it would be rougher...

 

[cr9c1]

Re: 73 Johnson 9.5 rough idle

All new gaskets, nice and tight. I thought about this too, but I'm more inclined to think that it may be more varnish behind the plastic plug (That I have not been able to remove to this day) that sits behind the larger core plug, and is in back of the 3 small tiny pinholes in the bottom of the throat of the carb.

 

[iwombat]

Re: 73 Johnson 9.5 rough idle

so, the 9.5s will almost always run rough in the barrel at idle. They suck up a lot of exhaust unless vented properly like on the transom of a boat. I wouldn't put too much stock into what you're seeing until you can reproduce it on your boat in the water.

 

[F_R]

Re: 73 Johnson 9.5 rough idle

Yes, I am wondering if by "rough", you mean shaking? They normally flop around quite a bit. However, they also have a lot of problems with the front rubber mount breaking, and then they REALLY shake. Grab hold of the flywheel and see if you can move the powerhead fore and aft. A bit of rubber movement is normal, but if it flops fore and aft, the mount is broken. A very intimidating repair for the novice. Can I assume the vibration dampers are in place on both sides of the powerhead?

Do you have the two friction washers in the steering co-pilot? They go directly above and below the slotted arc piece.

 

[cr9c1]

Re: 73 Johnson 9.5 rough idle

By rough I mean it not shaking, but not smooth. I've checked all the mounts and they're fine. I've had to replace them before so I'm familiar with how to do it. I checked the mounts before I bought the motor.

It just basically doesn't seem to be very smooth at all if you up the RPM's and bring them back slowly. It sounds like it isn't getting enough fuel. It seems to be slightly better if I use a garden hose to spray near the exhaust and haul it away from the motor. So I'll try it on the lake and see what happens then. If not, I have an idea that there may still be some gum in the carb somewhere because on the large core plug, in behind the plastic piece behind that it looked like varnish on the other side but I couldn't tell. I had carb cleaner flowing through all 3 small holes.

As far as the steering, and as I can tell, I have all the necessary parts including the two friction washers (One on top of the arc, one on bottom), the spring, square nut, and the washer with the ear on it. I pulled the guts out of it to see if anything was stripped but it didn't appear that way. It just doesn't seem to tighten up as much as I'd like and basically sits there and spins.

Thanks for the input so far.