Results of balanced prop/new SS shaft

[Kyle Ewing]

Donnybrook went up the river Saturday.  For those not familiar with Chicago river runs, imagine going under 15 draw bridges and one river lock over a two mile stretch through downtown Chicago with 30+ other sailboats.  It went mostly without incident and Donnybrook is now safely home at Belmont harbor.  I look forward to our second season together.

Off-season I found a loose cutlass bearing so I decided to replace it.  While off I took the original bronze shaft, propelor (15 x 9 3-blade), and coupler in for checkup and found a slightly bent shaft (could've bent as I worked it around the rudder) and 2 of the three blades out of spec pretty bad.  It surprised me since it seemed to run very smooth.  There were no nicks or anything else on the prop to indicate impact.

With the newly balanced prop, new stainless steel shaft, and a Globe drive saver (model 404A), vibration and noise are about the same (very smooth at most RPMs), but I have noticeably more torque as indicated by prop walk (a plus as I use it to my advantage when maneuvering in close quarters) and maybe half to a full knot more boat speed for the same RPM!  I also noticed that the engine wants to turn at 3500 RPM (overrev) vs. the 3300 RPM max I had before the prop balance.

The place where the prop was balanced (Airmarine in Chicago, who also made the shaft) said sometimes when blades go out, the blades can offset each other so you don't notice vibration.  I guess the prop balance may have caused the wear on the cutlass bearing (or maybe the loose cutlass bearing caused the prop to go out of balance) and may or may not have contributed to the bent shaft.  I was also told that an important area that is sometimes overlooked is the coupler to shaft alignment.  If there is any play at all, there will be a lot vibration.

Before I put the new shaft on, I went ahead and dropped the rudder as a precaution.  Its been written here that it can be worked around the rudder, but my experience was that it took A LOT of effort to get it out and I don't think I could've put it back in without messing up the new cutlass bearing or warping the shaft.

Kyle Ewing
C34 #1010, Donnybrook
Belmont Harbor, Chicago

[PAUL T.]

Kyle.... It is much easier to remove the propshaft if you remove the old cuttlass bearing first. Then put the shaft back in then the bearing. that little bit of extra room makes a world of difference.