Hi Dave, Is the lapping compound you used something like this?
http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/abrasives/lapping-compounds/lapping-compounds-prod1137.aspx Regards, Brian 1980 Landfall 38 On Mon, May 9, 2016 at 9:24 PM, Dave via CnC-List <cnc-list@cnc-list.com> wrote: > I replied earlier in haste, but another clue here is the forward-reverse > thing as well as the low rpm banging only. > The shifter moves a bronze clutch back and forth, this has a conical > surface on each each end that mates with one mating female cone for > forward, and the other mating female cone for reverse. In neutral, the > conical clutch sits between both and engages neither. Forward is used a > lot more, therefore it glazes first. > As to rpm- these boats do not have thrust bearings so the prop thrust > pushes forward on the engine/trans and ultimately the mounts. It does so > via the trans, so the thrust overcomes the slip at a certain point and the > banging stops. > Before long it will slip irrespective of rpm, and get so bad that you will > think the strut will be sheared off the hull. > Per instructions in the internet I used valve lapping compound. Did not > rebuild the gearbox, only lapped the cones. the halves use no gaskets, > just silicone. > I used a punch to mark the orientation of the cone and any other parts and > was very careful to clean any residual lapping compound out of the > transmission. > Worked perfectly. > Make sure you secure the prop shaft so it can't fall out. > > > Dave. > > Date: Sun, 8 May 2016 15:40:53 -0700 > From: Andrew Means <andrew.cnc...@gmail.com> > To: cnc-list@cnc-list.com > Subject: Stus-List Soft thumping/banging when in gear at low-rpm? > Message-ID: <etPan.572fc098.5095526e.13b@worsley.local> > Content-Type: text/plain; charset="utf-8" > > Boat: 1977 C&C 34 > Engine: Yanmar 3GM30 (F) > Prop: 3 Blade Max Prop > > Recently I noticed that when engaged in forward-drive, at low RPM, it > almost feels like something is banging against the bottom of the hull, like > a piece of kelp or rope tangled in the prop. Once the RPMs get above 1400 > or so the roughness goes away completely and everything feels very smooth. > > Sent from my iPhone > > _______________________________________________ > > 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! > > -- Brian Davis 1980 C&C Landfall 38 "Nina" <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> <#DDB4FAA8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
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