"Mid Size Power Boats": A Guide for Discreminating Buyers - by David Pascoe

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Troubleshooting Problems  
Involving Engine/Shaft Alignment
  

Photos by David H. Pascoe, Marine Surveyor

 

Photo #2 

This type of mount is fine for gas engines but not for heavy diesels. This mount, on a brand new 45 footer, is badly distorted. Note how it is cocked toward the engine and forward. In this case, the mounts allowed the engine to move so much that the shaft coupling came apart.

 
 

 

Photo #1 

Judging by the large gap at the top, his bearing looks like it is worn. Actually it is new but the shaft is badly misaligned with the strut. This is determined because the gaps are on the opposite side of the bearing at the front side of the strut. Thus, the shaft is "cocked" in the bearing. 

 

 

Photo #3 

The strut in photo #4 below carries the same size shaft and prop as in #3, both of which are in a 40' boat. But the #4 is double the thickness in both width and cross-sectional area, with a substantiallly wider base. There is no doubt that this strut will hold the shaft steady. Also notice that the length of the strut bore is double the length of that in photo #3. 
 

Photo #4 

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About Author:
David H. Pascoe is a marine surveyor (retired) with 40 years' experience.

He is author and publisher of power boat books:

"Mid Size Power Boats"
"Surveying Fiberglass Power Boats" 2E
"Buyers' Guide to Outboard Boats"
"Marine Investigations"

Visit  yachtsurvey.com  for more than 160 online articles.

David Pascoe's biography

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