I agree, it is scary. I may be double-counting the deflection - I'm just eyeballing it and looking at the apparent diameter which starts as a 1" shaft or so and shakes enough to look like a 2" shaft when in action.
Thanks for the ideas. On Thu, Jan 9, 2014 at 12:55 PM, Gary Russell <captnga...@gmail.com> wrote: > Wow! 1" of deflection is huge! Anything over 1/16" is out of spec. It > is strange that it is so bad in forward, but not in reverse. Is it > possible that the engine is moving in one direction in forward, and the > other in reverse (I know you checked the engine mounts, but did you observe > the engine while shifting gears)? Something has to be loose somewhere. I > doubt a defective MaxProp can cause that much deflection (I have one) on a > 1" shaft. > > Good luck, > Gary > S/V Expresso > C&C 35 Mk II > East Greenwich, RI, USA > > > On Thu, Jan 9, 2014 at 12:46 PM, William Hall <wh...@alum.mit.edu> wrote: > >> Dear List, >> >> I've been troubleshooting quite a vibration problem since I got my boat a >> year and a half ago. I had hoped it all just needed an alignment, but that >> does not appear to be the case. I'm hoping that if I present the situation >> someone on the list may be able to point me in the direction of a fix! >> >> The boat is Starfire, my 1985 C&C 37. It has a Yanmar 3HMF. I believe >> it's the original engine, but was overhauled a few years ago. The previous >> owner said it was overhauled because it was no longer producing enough >> power. >> >> The engine drives a 2-blade max prop. There's a line cutter on the >> shaft. There's an R&D marine elastomeric coupling between the end of the >> prop shaft and the engine drive shaft. >> >> When I bought the boat, we noted a lot of vibration when in gear above >> about 1800 rpm. The surveyor thought it needed alignment and noted as well >> that the max prop had more play in it than it was supposed to. I hauled it >> that first winter, had the max prop sent back to max prop for overhaul, had >> new cutlass bearing installed, and when it all came back together in the >> spring found the same vibration as before. When running in forward, the >> prop shaft deflects significantly at higher RPM's (maybe 1" of wobble at >> the worst point along the drive shaft), and things shake in a way that >> can't be good. In neutral, as well as reverse, it runs smooth as silk >> right up into high rpms. >> >> I've since had a few engine / drive people look at it and try to figure >> it out. The shaft appears to be true. The alignment appears to be right on, >> as measured by two different mechanics. The elastomeric coupling was a bit >> worn, so we put a new one in. The engine mounts are substantial and seem >> good. The engine people think there's something wrong with the prop that >> the overhaul didn't fix. >> >> What does the list say? Is it the prop? Could there be something wrong in >> the transmission, say a thrust bearing or something? In flat calm I can >> get almost 5 knots without too much worry of breaking things, but into a >> sea or wind I'd really like to have the option to use more power. What >> would you try? >> >> Thanks in advance for the thoughts. >> >> Regards, >> Bill >> >> 1985 C&C 37 - Starfire >> Stamford, CT >> >> -- >> William D. Hall, Ph.D. >> 203 653 2886 (o) >> 617 620 9078 (c) >> wh...@alum.mit.edu >> >> _______________________________________________ >> This List is provided by the C&C Photo Album >> http://www.cncphotoalbum.com >> CnC-List@cnc-list.com >> >> > > > -- > ~~~~~~~_/)~~~~~~ > > > _______________________________________________ > This List is provided by the C&C Photo Album > http://www.cncphotoalbum.com > CnC-List@cnc-list.com > > -- William D. Hall, Ph.D. 203 653 2886 (o) 617 620 9078 (c) wh...@alum.mit.edu
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