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Old 03-11-2017, 08:50 PM   #3
LarryM
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City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 936
Eric,

I studied the shaft and intermediate bearings used in Willard and Fales boats a couple of years ago when I faced a shaft vibration issue in Boomarang. It appears that Willard in many of the Vegas used the shaft/bearing design you have. Those Dodge flange-mount setscrew ball bearings are designed to be locked to the shaft precisely so that they cannot slide and wear. The inner bore of the bearing race and the shaft are not bearing surfaces. By locking the bearing to the shaft, effectively the intermediate bearings become thrust bearings. This obviously works, as there seem to be many Willards with this arrangement. I imagine the pulses you describe are largely absorbed by the mass of the flywheel to the point where they are negligible.

Fales chose Dodge babbitt sleeve bearings that support the shaft while allowing the shaft to move freely fore and aft. In this way, the engine thrust is transmitted to the hull structure via the engine mounts. The intermediate bearings only stabilize the un-supported shaft and eliminate whipping. With Yanmar power and their very flexible engine mounts, this is the only solution that makes any sense. This was also the arrangement for the original Perkins 4-107 as well. Boomarang's shaft moves about 3/16" (3/8" total) fore and aft with fresh engine mounts.

BTW, PSS now recommend locking collars on their shaft seal installations and sell them directly.
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