Process of elimination- vibration

[Florida]

I have a 25hp 2003 Johnson that shakes side to side in neutral and idle speed. At full throttle I can balance a wine glass though. What should my process of elimination be? For instance

1 carb clean
2 new plugs
3 new wire
4 fuel filter
5 ?????
6 ?????

There is no idle adjustment on the carb that I can see. The idle adjustment is external and is on the tiller handle. I don?t see a difference when I turn it either way.

thanks

 

[Texasmark]

Re: Process of elimination- vibration

First of all, how much vibration are you talking about? You have a twin cylinder (probably loop charged....Merc for that year is), alternate firing twin engine. You are going to get some shaking at idle because of only 2 cyl's (firing every 180 degrees of crank rotation) and the fact that it's loop charged (as compared to cross flow which are said to idle more smoothly).......but for me, that is no reason to want a cross flow.

The higher the rpm's the faster (closer together) the explosions and the vibration is reduced.

Does it misfire, or sneeze (mis a lick now and then). Does it respond to advancing the throttle; like taking off from a standing stop?

If your answers are no and yes, then I'd not worry.

As far as what you suggested, it depends on what the engine has been exposed to since '03. Sitting up, yeah the carbs could be dirty. Ignition wiring, on an engine that young, I'd doubt it unless they got damaged (physically) somehow.

Might try a decarb just for the heck of it; won't hurt anything and the engine will definitely like it; whether or not it needs it, who knows.

HTH

Mark

 

[Florida]

Re: Process of elimination- vibration

First of all, how much vibration are you talking about?

If I were to tape a newspaper to the engine at idle speed or neutral I wouldn?t be able to read it because it would be shaking back and forth. It does misfire and cough at times. When It does it nearly pulls the tiller steering out of my hand. I ran a half bottle of seafoam through the gas tank and it now runs smoother but still shakes. I don?t remember it shaking that much when I first bought it.

 

[tashasdaddy]

Re: Process of elimination- vibration

as mark said all 2 cyl shake even my 50hp. you might try to fine tune idle. but not going to help much. new plugs never hurt, if you do a lot of slow speed running. idle, trolling you can try opening the plugs, .005 to .010 more. they say it makes the trollers run better at slow speed.