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channelfats

Adjusting idle down

7 posts in this topic

I recently purchased a used boat with a 97 yamaha 30 tiller on the back. Motor runs great, except she idles a tad bit high for my liking. 1.5 in gear, and .6 in reverse... its kind of the annoying in-between, either use a trolling motor, or get the cranks out. How easy is it to adjust myself, or should I say, how much trouble can I get myself into? I am somewhat aware of how to adjust it, but how much before I mess up the oil injection ratio? Or if I even will... ? Am I better off taking it in?

Thanks

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Or, is this idle speed normal, and I am expecting too much from a 3 cylander. I am used to 15hp motors.

thanks

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Dunno if the idle speed is normal.

The engine mfg specs that by RPM. However, the speed depends on RPM, prop pitch, and boat size/weight.

Not sure about Yamahas, but Mercury idle speed on my 90HP is adjusted with the ignition timing. Tweaking that does not alter the relationship of the oil/fuel ratio.

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I have a 90hp merc 2 stroke. It idles my 17' at 2.8. Is this high and coulp I make it go slower. It has the original aluminum prop on it.

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I have a 90 merc on a 17 also. The boat speed at idle is 2.4 in forward. Thats at 500 rpm. I have a 21 pitch prop on. Those two; pitch and rpm are what matters. Setting an idle screw down will not affect oil mixture.

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I have a 50hp Honda and when I bought it new the idle was to fast. It has 3 carbs , there is a idle back off srew that the linkage rest or stops on, I backed that off to slow the idle. You can alway try that and set it back if its to slow. The carbs themself come set from the factory,the srews heads are removed or broke of so they can't be fooled with, but after a couple years and the motor getting broke in I reset the carbs a little richer because it was starting to die while trolling. A small punch and light tap in the end of the srew lets you adjust.

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Quote:

there is a idle back off srew that the linkage rest or stops on, I backed that off


This is right on.. if you look at the rod that connects the carbs together there's probably a screw threaded into a flange on the carb. Back the screw off a little bit to slow the idle down.

As others have said, idle speed is set by rpm... for a 2 stroke 550 - 600 in gear is typical.

marine_man

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