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1998 Johnson 90hp idle adjustment

G

gone_postal

Regular Contributor
"J90ELEC

It idles around 70

"J90ELEC

It idles around 700-800 when in neutral, but when I pop it in gear it drops to 400-500, bouncing around and stalls. It made slow speed trolling impossible the other day. It will also sputter and stall in neutral, but stays running longer - popping it into gear is w/in 10 seconds. I bought a factory service manual thinking it's something I could adjust myself, but the damn optical ignition requires a special tool that is $250 from what I can find. Is it possible that the timing is correct and just the mixture is off? (read there is a mixture screw on the carbs - found it, but don't want to mess w/ it in case it indeed is timing). Also, is there any way to do this without that tool?"
 
"Before You start, give the en

"Before You start, give the engine a Seafoam/engine tuner treatment.
Then check that Your spark plugs have even color to be sure that there is not something else wrong or going on.
Then You may adjust idle by moving the 'LOW' tab on the ignition adjustment."
 
"Well, only about 50hrs on the

"Well, only about 50hrs on the total rebuild - plugs & wires have only maybe 15. My mechanic recommended I take out VRO and put in a heat range hotter plug to help burn oil at idle (due to 50:1 ratio when it'd normally see 100:1 or so w/ VRO). Anyway, when my fuel pump went out, I decided to install new VRO tank & lines b/c the pump is usually the problematic part. I then went back to new stock plugs.

The motor also doesn't have thermostats. He said they're unnecessary here (FL) b/c it's rarely cold enough and when it is, you're not likely to find me on the water. I always give it ample time at the dock to warm up before I make a run, so I attribute "cold" stalls to that issue, but don't expect it to stall later when warmed up.

As for adjusting idle - which direction (bow or stern) will the tab increase idle? Also, what exactly is that changing? Timing advance / retard? How incremental is it? Is one notch a big jump? I definitely don't want to screw anything up, but I don't want to spend the $250 on the tool either. Might end up being worth my while though b/c a shop will probably charge me that much to correct this issue anyway"
 
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