250 HP SHO VIBRATION AT LOW RPM QUESTION

[johnwater]

need some advice on a new 2021 250 sho short shaft, that i put a driveshaft extension on to fit my bay boat transom.
just has not quite 20 hours on it so still in break-in mode, idles fine and hi speed runs great,.
only thing i notice is that around 2000-2500 rpm, just before going on plane noticeable shake/shudder/vibration from engine.once get up on plane, no issues.
any one know if this is just inherent on adding extension to drive shaft? was done by Dealer,they say they have done many before.
i am due to bring it in for 20 hr checkup, will let installer know of course, anything else i should look for?
thanks
john

[BroWhoop]

No expert here! Could it be the prop as you're just getting on plane. A slight slipping or cavitation. The transition of getting on plane is where you can have these kind of issues. You even post this in the setup or prop forum.

[21XDC]

The propeller was my first thought as well. Known as exhaust rumble. Normally it happens at lower speeds

[HH45cal]

Bent prop shaft?

[bgibson]

I am with prop cavitation as well. No worries!

[ClarkBird]

Throttle up when it starts and slip it until she breaks over and hooks up.