250 SHO idle vibration

[bkeenom]

Seri 6CBL1000022

2010 250 SHO
Idles smooth and quiet when in neutral. When in gear and idling it seems to run rough or have something vibrating. Very smooth when accelerating and running. Can't pinpoint the issue. Any idea on this issue?

[McQuaig]

Sounds like "prop chatter" or "prop rattle"...fairly common with 4strokes, sometimes not noticeable but sometimes more, depending on prop. If you do a search on here (BBC) there are lots of threads on it.

[tracer1]

Maybe a slightly bent prop shaft also. I know the SHO has a close tolerance for the shaft. Mine was out of alignment a little. Dealer straightened it back to Yamaha tolerance. I'm just guessing, as I'm no where near a mechanic, but you might check that also. In idle, the prop is barely or not at all moving. In gear could be the vibration from the shaft.
Hey McQuaig, did you get the hub kit squared away?

[bkeenom]

Checked the shaft and it is straight.

[tracer1]

Oh well, just a thought.

[McQuaig]

I do think it's prop chatter (I'm having the same issue with a new 4 blade prop, which I intend to solve with a "softer" hub kit when I find it). It doesn't happen with every motor, but it's caused by a combination of 4stroke engine pulses, lower idle speed and heavy/stiff SS props, especially 4 blades which are heavier than 3 blades. To check for sure, if you could borrow a 3blade with rubber hub or an aluminum prop just to try in gear at boat ramp (pitch won't matter since you don't have to run on top) to see if the sound/vibration goes away.

[bkeenom]

I do think it's prop chatter (I'm having the same issue with a new 4 blade prop, which I intend to solve with a "softer" hub kit when I find it). It doesn't happen with every motor, but it's caused by a combination of 4stroke engine pulses, lower idle speed and heavy/stiff SS props, especially 4 blades which are heavier than 3 blades. To check for sure, if you could borrow a 3blade with rubber hub or an aluminum prop just to try in gear at boat ramp (pitch won't matter since you don't have to run on top) to see if the sound/vibration goes away.

Or try without a prop to rule out issues in and above the lower unit.

[bkeenom]

Tried it without a prop and quiet as a mouse. What hub kit what I need stop this?

[McQuaig]

Tried it without a prop and quiet as a mouse. What hub kit what I need stop this?

There are a couple replies on the thread below this caledl "hub kit" that might help you. Whatever you go with I'd appreciate your results since I have the same issue but I can't do anything until spring...thanks in advance