Thanks guys for the spark plug tips. I never thought about gap alignment before, although I have played around with changing the gap on problem motors with mixed results, and I have put a higher heat range plug in one cylinder if the plug consistently comes out looking wetter/blacker than the other and this often works! Orientation of the electrode may explain why a 9.9 Johnson I worked on 3 years ago went from terrible to perfect idle when I put in new plugs, although I did change from Champion to NGK. Maybe the alignment just happened to get right with the new ones?…although NGKs just seem to work better in some motors.

Dave

Thanks again for the info – never too much info – something here is likely to make it idle right. I have new B7 plugs in it but have some B6s I can try. I have tried the idle screw out as far as 5 turns. It does a very slight bit better 3 or 4 turns out than at the recommended one turn, and no change beyond that, but still not at all good. I’ll be digging into it again in the next couple of days. The owner needs a slow idle to back-troll for walleyes.
Dave

Ok – I dug into this motor again today. Compression is fine – 90 on both cylinders.

I think I’m getting somewhere with the carb: I pried the welch plug off the top of the carb and it gives access to the three idle holes going into the carb throat – I ran a wire through them and they are fine. I notes that only one hole is downstream of the carb throttle plate. The welch plug also gives access to the downstream side of the hole the low speed needle point sticks part way into, with the needle removed, I ran a wire through that it and it was clear, also blew carb cleaner back through the needle cavity from the small hole accessed via the welch plug. That welch plug did not give access to the needle valve’s bearing. I shined a flashlight into the needle valve’s mounting hole and could see something that looked no good at the end. With a small wire bent into a hook, I managed to pull out a small glop of what looks to be foreign material. It was "mush" when I squeezed it. It was much too small to be a partially carb cleaner dissolved bearing. It looked suspiciously like the crystalized stuff I found jamming the entire length of the float valve needle when I first took it apart, so it could have been some of that stuff that must have formed when gas (maybe gas with ethanol or some strange additive?) dried up in the carb, and the carb cleaner may have made it mushy.

When I looked into needle valve’s mounting hole with the flashlight, at the far end I am not sure if I’m seeing a bearing or not (hard to see up there), but I think I am because I am seeing detail that looks like the radius of the bearing housing and the center hole looks like it would match the cylindrical machined surface on the needle valve assembly just behind the actual needle – seeing this hole, does this mean the bearing is in there? The hole I see in the welch plug area coming from there is much smaller for the needle tip.

So now I will get a carbkit – need a new welch plug for starters.

More Questions:

1. Does a new bearing come with the Sierra Kit? The OMC kit? I think I’m seeing it in the OMC kit but not the Sierra in online photos, but it’s hard to tell. Otherwise, I see I can buy the bearing separate, but may not need it.

2. I’d like to make sure all idle passages are really clean, and that means removing the lead shot plugs. I’ve never done that before. Any tricks to shot removal/replacement? An old Clymer manual says to pry them out with a sharp knife, awl, or other sharp instrument. To install new shot it says to use a hammer and appropriate size punch. Any really slick ways to do this that anyone has found?

3. I’m not seeing lead shot in the carb kit photos. Can I use small fishing sinkers, squeezing them shut and , if needed, sanding the size down? I see part #0304201 lead shot at Marineengine.com for $8.93. Does that get me a few in a bag, or is that a price for one? The carb has 4 of them.

Thanks again for all the tips. To summarize, I think I’m onto something with the bad idle finding that glop of stuff up by the needle bearing area, and likely more in passages I will get to by removing lead shot. If knowing all carb passages are clean doesn’t get me a good low idle, I will then try the spark plug electrode tips.
Dave