Martec non-geared props have issues with both blades opening especially if they get worn at the pin in each blade. Sounds like that might be the issue. Was on a J/35 in the late ‘80’s that had that issue and the whole boat would shake. The owner and his son had a routine they went through to coax both blades to open; IIRC they went to neutral, then reverse with some throttle, then relatively quickly went into forward. Might guess that put some additional wear on the cones in the transmission, but it seemed to work.
Martec will recondition the props, but that obviously means pulling the prop and sending it to them… Many of us who had Martec’s have changed to Flex-O-Fold geared props to eliminate the potential to vibrate due to a blade not opening and for much improved reverse. Have my old Martec if anyone wants it: RH 16 x 14 for a 1” shaft… Brian From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Kevin Paxton via CnC-List Sent: Sunday, May 27, 2018 10:46 AM To: cnc-list@cnc-list.com Cc: Kevin Paxton <kpax...@paxdesigns.com> Subject: Re: Stus-List 3GMF knocking sound Pretty sure it's a martec, folding 2-blade. I try to power up and it vibrates like crazy. I power down to try and get it to reset so that I don't damage anything with it vibrating so bad. Then I try again. If I rotate the shaft manually I can hear each blade folding open but for some reason it is tough to open it after sailing for a bit. Coming out of the slip it opens without a problem. The sounds came this time though while already under power and the prop was open. On Sun, May 27, 2018, 10:27 AM Gary Nylander via CnC-List <cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com> > wrote: I’m curious. What kind of prop do you have that requires you to slow down to get it to open. Most folding ones ask for more speed to get the blades to open. Non opening would produce lots of vibration, which would get lots of noise as the engine bounces around on (particularly) old motor mounts. Shake the motor. Gary Flex-o-fold geared
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