Rudder Vibration from Prop

[seaesta]

Dear all
I have a vibration which starts when I rev my beta 13.5 in drive at over 2500 revs. Lower revs will push her along at 5 kn but I need more to comfortably run at 6kn. The stern tube and shaft seem to be fine but I have noticed the nut on the tiller working lose and the vibration feels like it is coming from steel tube housing the rudder shaft. It seems that the problem may be a vibration caused by the pressure waves or pulses of water flow as the prop rotates and these strike the rudder. Has anyone else had this and what have they done about it? Hope you can help
Martin

 

[Bilgediver]

Have you changed anything recently???? New engine....new propeller...?????

Sometimes if the propeller is too close to the rudder it produces vibration as you describe. This is especially true of rudders with propeller cutaways like Contessas.


John

 

[bumblefish]

I also get some vibration on the tiller but then again the cut away on the Elizabethan leaves about 5-7cm between the end of the prop shaft and the rudder. I have to take the rudder down to get the prop off! I assumed it was just erratic flow over the rudder?

 

[seaesta]

It happened since I fitted the new engine. I have lived with it but would liek to sort it out over the winter. Will measure up when I get her out next week and may mod the rudder and will certainly fit new bearing to rudder shaft
cheers
Martin

 

[Sans Bateau]

Used to get something like this when we owned a Sadler 26, If I remember correctly it was because the bearings in the (transom hung) rudder pintle were loose.

Other than that, get someone to drive the boat at the offending speed while you have a look at the engine with the covers off, see if the engine vibrates. Engine mounts?