85 johnson 120 - idle again with video

Well I'm back working on my engine again. Seems I take a few months off, enjoy the other boat, then come back to this one.

Here's my problem. I cannot get the engine to idle down to the right rpms in water, without it wanting to die out. I get it down to where it needs to be and it gets really bumpy and sometimes just stops. So I'm stuck setting it a little higher in gear, maybe 900-1000rpms, but when I shift into neutral, the rpms go up to 1400-1800. If I clunk it back into gear it drops down to 800+ or so. I have done a link and sync and the throttle plates are closing 100% when in neutral.

I've done the most obvious things here including rebuiling carbs (reset float 3 times), check for air leaks, new fuel lines and tank, cleaned recirc valves, new veranatherms, new waterpump, I re-sealed the gearcase borrowing mechanic's tools, set idle and WOT timing, and more I probably can't think of right now. The engine runs perfect off idle, through the rpms to WOT with no hesitation and all out power. I just can't get it right. I've included a video since a picture is worth a 1000 words. Please advise me what to do next.

http://www.youtube.com/watch?v=tiX0X3tdRsA

couldn't get embed to work, so direct URL above.

Re: 85 johnson 120 - idle again with video

You will always idle slightly higher on muffs. On the water you will want to be around 750-850 rpm, usually like 1000-1100 rpm on muffs.

Re: 85 johnson 120 - idle again with video

My problem is, when I'm on the lake, in order to set the idle close to "spec" without the engine dying, it becomes a really high idle when I put it in neutral (still on the lake). The idle is close to around 900rpms or so on the lake in gear. Any lower it bumps around a lot and dies. The last 2 minutes of the video really show exactly what it does in the water, but with different screw settings to compensate for back pressure since it is on the muffs.

Re: 85 johnson 120 - idle again with video

Have you checked the compression and spark?
When you had the carbs apart did you make sure the idle orifices were clean?

Re: 85 johnson 120 - idle again with video

Indeed, that was one thing I forgot to mention. I checked the powerpack with a CDI peak reading adapter for my voltmeter. It's getting good spark.

Compression is 120-125psi on all 4.

When I had the carbs apart I disassembled all jets and ran small copper wires through them. I ran a wire up the pickup tube as well and carefully blew out the passages with carb cleaner and air. I used a led flashlight to ensure my passages were clean by shining light through them.

I've been reading the spittle through the carb and rough idle could be broken or chipped reed valves, but I don't think that's a common thing. All 4 carbs have the occasional spittle. Maybe the carbs are just bad? I really dislike these plastic carburetors.

Re: 85 johnson 120 - idle again with video

It's probably stupid of me, but I ordered a new powerpack anyways. I figure it wouldn't hurt to have a spare and the old one looks like an original part number - though it did pass the voltage test.