Dave,
A couple other things to explore beyond the engine / shaft alignment already mentioned: A possibility might be the hub of the Flex prop is not seated properly on the shaft and therefore is off center. If the key moved out of position as you slid the hub on, the hub could ride up on it and not be fully on the shaft. The cutlass bearing may be worn, especially if it had several years of operation with that out of balance Martec prop. Try to dive on the boat and see if you can move the shaft at the strut. A rule of thumb I heard years ago is anything more than 1/16” of play is too much and the cutlass needs to be replaced. Another possibility is the shaft is not true. The prior owner might have caught a lobster pot or other line and bent the shaft. While the prop could be reset while in the water it would require a knowledgeable diver and some of the pre-coated set screws that came from Flex o Fold with the prop. Otherwise, a short haul is in order, or living with it and chase down the cause(s) after hauling for the winter. I did get the 16x12 blades for my old Flex hub [replacing the 16x13 blades originally sold to me] and it made a significant difference in reducing vibration. Good luck Brian From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Robin Drew via CnC-List Sent: Tuesday, June 14, 2016 10:39 PM To: cnc-list@cnc-list.com Cc: Robin Drew <cncforum.ro...@gmail.com> Subject: Re: Stus-List Awful vibration Did you check you engine/ shaft alignment? It's a common cause of vibration. Robin On Jun 14, 2016, at 8:55 PM, Dave via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: I purchased my boat, a 1984 35Mk3 three years ago. The first season the boat would vibrate badly when I'd slow down under power. I'd put it in reverse, throw it into forward (ouch) and things would be fine. The blades always opened initially when I motored off the mooring but if I slowed down the flow over the blades exceeded the centripetal force and folded one of the blades and not the other . So, that winter I sent the 2 bladed prop back to Martek to have it rebuilt. They said the blades were so badly oxidized that they couldn't weld them to build up the stops so, they replaced the blades with another pair (used) they had available. To be sure the problem was fixed I also had the cone clutch in the transmission replaced. Last summer the only thing that changed was that the boat now moved forward when the lever was pulled back to reverse and visa versa. The vibration still happened under the same scenarios. Having had the blades replaced and the transmission rebuilt there was no way to tell whether it was that the blades were the opposite hand as what I had previously or if the transmission was done incorrectly. This spring I purchased a 2 blade Flexfold geared prop and guess what, the vibration problem is still there and forward and reverse are still, yep reversed. So, I know that the direction issue is the transmission and that is easily fixed by rotating the linkage arm. But, I'm totally baffled as to why the vibration problem has not been resolved. So, if anyone has any suggestions or ideas they would be greatly appreciated. Dave J Saltaire C&C 35Mk3 Bristol, RI _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
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