engine vibration

[Leo]

After moving Sol to the San Juan's we have a lot more vibration from the engine. I read that any time you move a boat it should have the prop shaft realigned. I also read that motor mounts need replace every 7 to10 years.
Has anyone out there changed out your motor mounts? And did it make an improvement? Did you use Westerbeke mounts or an aftermarket? Any insight on mounts or alignment of the v-drive would be appreciated.   

[PeteW]

By "move" I'm assuming that means lifted out of the water and placed on a trailer?  And by "lot more vibration" you also mean "and all of a sudden". If that's what was done the evidence points to a bend prop shaft. A consequence of a misplaced lifting strap. Check the prop shaft run out at the stuffing box with a dial indicator.

I never heard of having to realign the shafts after a haul out. The rule I follow is never attempt to align any shaft flanges until the boat is in the water.

Pete

[Leo]

The boat was pulled out of the water and moved. No problems with the shaft I was present when it was hauled.

[PeteW]

The reason why I recommended checking the drive shaft for run-out is because  its the only rigidly mounted shaft in the drive train and it must be straight and it must be perpendicular to the v-drive flange to better than 2 tenths of a  one degree. ( Using Trig, the inverse tangent of a  .003" feeler gauge divided by a 1" diameter coupler flange)


Secondly I know from experience that the V-drive will raise up 1 inch or more when the 365 is placed on its keel.  Using trigonometry again, this  movement places a tremendous amount of bending force of at least 1 degree  on the shaft, its coupling flange, the v-drive and its mounting brackets. So while the boat was lifted onto the hard I am saying that something got bent, broken or tweaked. And when the boat was returned to water that something did not return to what it was. ( It might actually be wise to loosen the 3 flange bolts on the  prior to hauling the 365.)

Pretty amazing that you could conclude its not the drive shaft simply because you looked at it from 50 feet away. The run-out I am talking about  might only be 10s of  thousandths of an inch. If the shaft is straight check the coupler flange for .003" or better alignment. This is the correct order you must follow. I forgot to mention a bent strut which will show up irreconcilable misalignment to either port or starboard.

The input shaft alignment and motor mounts will be the last thing you check. The drive shaft to v-drive must be 3 degrees or less and the U-joint/gearbox flange must be perpendicular to the drive shaft to better than 1.5 degrees. Using dial calipers and trigonometry you can measure and record the u-joint alignment values (vertical and horizontal) with accuracies better than one tenth of a degree. Write them down so that you can go back at a later date to see if anything moved.

Pete

[SVJourney]

Pete,

This brings up an interesting question.  I am overhauling the V-Drive on journey as it is sitting on its keel in the yard.  From what you are saying, it is not possible to check for a bent shaft or align the box while its in the yard?  That means I must launch, check the shaft alignment, then haul out again and replace the shaft if needed.

At this point it sounds like I should just remove the shaft and check it on the bench to make sure its straight. 
We had a fairly significant visible vibe at the packing gland, so I am almost sure that it is bent.
Anybody know if the shaft can be straightened?  Or have a source for a new shaft?

Wayne

[SVJourney]

Leo,

The best instruction to aligning our drive system that I have seen is the Walter V-Drive manual.  It give the procedure, with illustrations and tolerances.  Here's a good electronic copy from Sea Dragon's website:

http://www.sailingseadragon.com/Manuals/Walter_V%20_Drive.pdf

Wayne

[Jim S]

Since you have already uncoupled the shaft from the v-drive, having a machinist check the shaft for straightness would be prudent.  The original shafts are now 30 plus years old and better materials are most certainly available.  Phantom was repowered in 2005 with more torque on the shaft.  The original shaft, a bronze colored metal, was true, but the increased torque of the new engine, v-drive and propeller caused a whiplash effect that caused knocking above 1700 rpm.  A new stainless alloy shaft, aquamet I think, remedied the problem.

Since a lot of 365s are hauled each year and set on their keels with no widespread reports of shafts being bent from an unknown cause, my suspicion is that a "settling effect" probably is not the cause of the vibration.

[INCOMMUNICADO]

Wayne,At one time we had a good prop shop here in Jax. but can't reccomend any that are left. New shaft Deep Blue Yacht Supply A-22 stainless 82 3/4 x 1 2/1 single taper. 393.72 tax 23.62 shipping 18.14. They shipped it in two days. Allen

[Jim S]

Is the shaft 1 1/8 or 1 1/2?  Mine is 1 1/8.

[PeteW]

I pulled my shaft when I did the last haul-out and ended up having to make a new one for $550. I don't know if it was bent but it was deeply scored around the stuffing box. Also the cutlass bearing was down to nothing.

I do believe you can spin the shaft in the boat and check it with a dial indicator for straightness, but you need to loosen the coupler flange bolts first. Here's why I say that:

A SS prop shaft is also a spring , or torsion rod. Whatever misalignment exists between the shaft coupler flange and the V-drive will exert a torsional force on the shaft and the v-drive mounts. This force will spring load the shaft and cause it to run elliptical. Every 180 degrees of rotation will show up as a high and low spot on the shaft. Besides transmitting vibes through the hull it's not good for the stuffing box or cutless bearing either.

My hypothesis is that this spring loaded distortion of the prop shaft caused by misalignment is what causes the vibration. I'm suggesting that you should be able measure this with a dial indicator spinning the shaft by hand. I would also expect to measure some up and down rocking movement  at the V-drive itself.

When doing the alignment I follow the Walter procedure but have improvised measurement techniques that give greater accuracy. It all involves right triangles. By enlarging this right triangle to a couple of feet the error of my measurement is greatly reduced. Useful when you align the motor to the V-drive. (you don't align the v-drive to the motor)

The Walter u-joint alignment measurement requires taking the difference top/and bottom left/right of the flange to u-joint knuckles. I convert this to degrees by using the well know identity: Tan = opposite/adjacent, so that the misalignment in degrees = Inverse Tan ( a-b/diameter of the flange). We can better relate to degrees.

As Dale pointed out some time back, misalignment of the input shaft to the v drive will not cause vibration because the angular velocities are cancelled by the double Cardan u-joint in the v-drive. But misalignment of the u-joint to gearbox flange will cause vibration because  angular velocities will increase exponentially with misalignment. Based on the Walter spec this calculates to not more than 1.5 degrees.

This means that the compromise in aligning the motor to the v-drive would be to favor better u-joint alignment at the expense of input shaft alignment for smooth operation at low RPM. Something you might have to do if you run out of motor mount adjustment. When I aligned my motor the u-joint alignment was 0.95 degrees on both axis. Something you can't measure with a protractor. I could only achieve this by accepting less than ideal 2 degrees of input shaft misalignment. (I bottomed out my front motor mount  adjustments)

Pete

[Leo]

I got back to Sol and found that the bolts on the port side of the v-drive were loose! Problem solved.
Thanks for all the great info, learn every time I start a new project.

Thanks,

Leo