Vibrating shaft at slightly high revs.

[delmarrey]

What do you mean by isolators? Are you talking about the rubberized motor mounts?

[Hoohaa]

Stay tuned guys. I have recently installed a new diesel engine. New mounts. New engine bed. And am fine tuning the alignment .
Currently, after doing all this work. The wobble is still there.
But I have come to realize that my past alignment skills were crap. So I am now using feeler guages in conjunction with a drill bit. It's changed my world.
But it still has a little bit to go.
Here is where we are now.

[Hoohaa]

[Hoohaa]

[Three Sisters]

Congrats ! The motor mounts look terrific and appear to be easily adjusted with two wrenches. A pleasure for future checks and fine tuning.

[Hoohaa]

I had another crack at aligning the motor today.
I got it all under 4 th. But when I tightened up the mount bolts the figures changed
Top o
Bot 6
Port 6
Starb 0
Its not bad but I still have the wobble.
The fact that the alignment moved when I tightened it down suggest that I don't have equal weight on all of the mounts.
Is there a way to get the loads even?
I am also replacing the flexible coupling to eliminate it from the equation.
Here is a quick update of what's gone on so far. Including to goes at alignment by marine mechanics.

New shaft
New prop
New mounts
New engine
New rebuilt strut
New cutles bearing.

So you can eliminate all of these things.
Also. The wobble is visible when you turn the shaft by hand. So it's not cavation off the hull or shaft balance.

[Chenega]

Look into a SigmaDrive. A great product / coupling system

[jimbunyard]

Did you have the coupling and shaft assembled and checked/turned prior to installation to ensure that the coupling face was exactly perpendicular to the shaft axis? Did your new engine come with a new transmission? If so, I assume it came with a new output flange? (In other words, the output flange should be perpendicular to the trans output shaft from the factory...)

[a64pilot]

If it doesn’t run true when turning by hand, it’s bent, or the alignment is off.
Yes do look up a Sigma drive, it makes alignment irrelevant. Tied to the dock, mine runs as smooth as glass with a Sigma Drive but underway it vibrates, meaning for sure it’s the prop not liking the induced flow, likely cause I have so much dead wood with my thick keel

[Cheechako]

By "wobble " do you mean visual or vibration? Some just look wierd visually. Is the boat in the water? .006 is certainly close enough if it's not. Recheck in the water.

[Hoohaa]

Jim.
The gearbox hasn't been changed. The only alignments performed this time . Have been by myself. I have had it done twice before, professionally. Without success.
The current alignment is being done in the water.
The shaft was New 2 years ago, so is definitely not bent.
Those Sigma drived have definitely sparked my interest. I am going to contact them tonight.

[Hoohaa]

Chee
Its a visual vibration.

[a64pilot]

The Sigma Drive is nothing more than a Rzeppa joint, first I saw of them was on the front axles of Military trucks and jeeps, friend had an M38A1 Jeep built by Ford that had Rzeppa joints on its front axles as well Deuce and a half’s and five tons.
I bring that up to show it’s a proven design, nothing new here. Brunton I believe bought it from someone, but in a boat it’s under a light load relatively and ought to last indefinitely.
https://en.m.wikipedia.org/wiki/Alfred_H._Rzeppa

[Chenega]

https://kingpropulsion.com/wp-conten...D-banner_0.jpg

Have seen similar issues solved with SigmaDrive. Lead me to install one solving noise and vibration issues
- no connection to them

[a64pilot]

There is no keyway in the Sigma Drive, it holds the shaft by friction alone. It’s a tapered cone that gets pulled into the drive constricting that silver collar around the shaft.
I believe it may slip if you wrap a line or something that stops the shaft, and you can vary driveshaft length by quite a bit depending on how far it’s inserted into the Sigma Drive, it can stick all the way through.
However The bolts are I believe grade 8 and therefore carbon steel, be sure to put your favorite rust preventative on the bolts. The picture shows silver bolts, ones I got were black and I believe very susceptible to rust.