Rough Idle

[Charley]

I have a 75 HP. Yamaha (1997) 2 stock. Has a rough idle it will kill at closed thoutle. It runs rough intil 4500 RPM Runs fine from their on up. Put new plugs in. Any ideas?

[overdalimit]

Check the timing, clean the carbs, check the compression, make sure the gas is fresh, run the old stand by seafoam through it and let us know if it made any difference at all. You want to do the easy stuff before you dig deeper.

[Charley]

Gas, I been fishing a nummber of times put 15 gal. of gas in thurs. I run seaform a number a times in a season. Its ran great all year so far. Was on Leech all the day before. Again ran great.

[marine_man]

Sounds like you need to clean your carbs out... sounds like the low speed jet is partially clogged / plugged.

marine_man

[Charley]

What would clog a jet on a carb?

[jeffreyd]

dirt in fuel, varnish from old fuel, piece of hose that came off several things.

[marine_man]

Absolutely.... most notable varnish from old fuel.

marine_man

[Charley]

Even if you store it with seafoam in in it?

[marine_man]

It's possible...

It kind of depends on if there was some buildup prior to storing it with seafoam, or if there's gunk in the carbs (which seafoam wouldn't do too much for).

marine_man

[BoxMN]

That is what was wrong with my 25hp, after I bought new fuel line, new gas tank, rebuilt fuel pump... all it needed was a shot of air through the jet... doh! Easy fix, I would measure how far the jet is from "all the way tight" - I put tape on screwdriver and then count the turns, its a bit easier to keep track for me

Then take an air compressor and give it a shot or two of air. Worked perfect for me. Good luck.

[Charley]

Well took it too Hannays the diaphragm was bad. One thing they told me was the corn whiskey gas they are selling is not good for outbroads.

[jeffreyd]

heck it is not good for anything boxmn. not even drinkin

[marine_man]

The diaphragm in the fuel pump?

Glad to hear you got it squared away.

marine_man

[Charley]

Marineman- In the carb.

[BoxMN]

Is there a diaphragm in the carb?... I don't recall seeing one in the ones I did, but there could be a combo carb/fuel pump I guess.

I do recall needing a new daiphragm in my Dad's motor when I was young, but I can't recall any more than that. Glad its working again for you!

[marine_man]

No, I don't believe there's a diaphragm in the carb.

marine_man