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Current Replies for Mark II Prop Shaft Question
 
  Mark II Prop Shaft Question (rgoeke)
Posted: 6:47:54 pm on 6/24/2012 Modified: Never
 
Hello, I made the mistake of thinking of could pull the shaft on my 1973 C&C 27 Mark II to replace the stuffing box hose.  Wow.  I finally have the coupler off (after cutting the bolt heads) and am about the simply cut the shaft as close as I can to the coupler.  I'm hoping I may have enough extra length on the prop end to simply move it up so I can re-use the shaft.  If not, has anyone replaced their shaft recently.  Is it a double tapered shaft?  I just ordered a split coupler from Moyer Marine.  Anyone try one of those?  Thanks a bunch and all the best!  Rob Goeke
  Re: Mark II Prop Shaft Question (Roger Gibb)
Posted: 8:57:00 pm on 6/26/2012 Modified: Never
 
Yep - had to replace my prop shaft last year after a lurking deadhead attacked it in the Strait of Georgia.
To answer the specific question: the inboard end was not tapered.
More info:
The 4 bolts on the union came out quite easily after a good soak in Liquid Wrench (cutting them off must have been quite a task!!). The union attached to the prop shaft also came off fairly easily after soaking the square headed bolts in Liquid Wrench and some gentle tapping with a hammer. As I recall the end was shaped where the square headed bolts landed, but I could be wrong. I did not need to apply heat, fortunatley. Because the shaft was distorted by 30 thou or so (with associated vibration) I had a new one milled for about $400 out of 7/8" ss stock. Since the shaft is out anyway you may choose to have it checked for trueness. I also replaced the cutless bearing since I had gone to all this trouble.
The problem with shortening the prop shaft is that the prop tip clearance will be reduced significantly, resulting in possible excessive turbulence and vibration (prop tip clearance should be greater than 15% of the prop diameter).
Good luck

Roger Gibb


Passtime (27-4)

  Re: Mark II Prop Shaft Question (rgoeke)
Posted: 3:46:24 pm on 7/4/2012 Modified: Never
 
Thanks Roger.  I have it all apart and am going to go with a new ss shaft per your suggestion.  I will send photos.  I'm also going to replace the cutlass bearing.   I cannot tell for certain if the outside diameter is 1 1/4 or 1 3/8.  Do you happen to recall by chance?  Thanks again!  Rob
  Re: Mark II Prop Shaft Question (Roger Gibb)
Posted: 9:04:15 pm on 7/4/2012 Modified: Never
 
I'm sorry - I'd be guessing as I don't recall.
FYI I have recently added a R&D Marine flexible coupling between the shaft couplings - that helped extend the shaft length about 1.25", and increased the prop tip clearance about 3/8" - enough to reduce the vibration caused by turbulence considerably. I originally ordered the ones recommended for Yanmar (I have a Yanmar 2GM) but they were way too large, so went with 800-037, which replaced the original mounts nicely. (It is very important to also buy the electical insert to ensure electrical continuity through the coupling, otherwise bye-bye zincs and prop in short order).
Roger

Roger Gibb


Passtime (27-4)

  Re: Mark II Prop Shaft Question (Roger Gibb)
Posted: 4:58:07 pm on 7/5/2012 Modified: Never
 
I apologize, I seem to have indulged in a seniors moment in my reply, so here is a corrected version (I somehow got into engine mounts, which I have just replaced and were top of mind!!).
I'm sorry - I'd be guessing on the cutless diameter as I don't recall.
FYI I have recently added a R&D Marine flexible coupling between the shaft couplings - that helped extend the shaft length about 1.25", and increased the prop tip clearance about 3/8" - enough to reduce the vibration caused by turbulence considerably.
Roger

Roger Gibb


Passtime (27-4)