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Old 09-13-2019, 01:36 PM   #1
City: huntington harbour
Country: US
Join Date: Jul 2015
Posts: 2
Metal to Metal Sound from Drive Shaft

Hello All:

I have a DF41, with Twin Lehmans and Velvet Drives. The Shafts go through a two stud packing box arrangement, out the boat and through a strut with a Cutlass Bearing, then the props.

Sometimes (Usually after sitting for a few days), when I engage the port transmission in idle in the opposite direction from the Stb trans, I hear a medium to high pitch noise that sounds like metal rubbing on metal. The noise goes away when I go back to neutral or raise the rpms to 700 or above. It then may come back at the next counter rotating turn, until I start cruising and then I will not hear it again for that entire trip.

I keep from 2 drips per minute to 10 drips per minute for each packing, and I replaced the flax packing completely and the noise came back. My packing consists of 2 pieces of 5/8, and 2 pieces of 5/16 at an inner step of the packing. The drive shaft is aligned per the .003 feeler gauge, but there is about a 1mm off set trans flange to stbd, and shaft flange to port. Bolts slide in easily without any persuasion. The engine mounts are currently maxed out and I cannot remove this 1mm offset. I've put on thousands of hours, and replaced packing about 5 times in 10 years before this started. Upon diving I have noticed the cutlass bearing could use replacement at the next Haul. (With most all my strength on the prop, I can detect movement even if it is unmeasurable)

Based on another forum search, it seems like two possibilities are 1) a singing prop from thin inconsistent prop edges, or 2) Rubbing on the shaft tube between the stuffing box and the strut. I also wonder if there could be some metal or an overzealous set screw in the cutlass bearing that sings a little in certain conditions and goes away with more of a load.

BTW: I have changed ATF on a regular basis, and not detected metal in the trans, and I'm 99% certain the noise is generated from somewhere between the front of the stuffing box, to the back of the prop.

I am probably still 12-20 months away from a Haul Out, and would appreciate hearing about any similar experiences or countermeasures applied to the inconsistent noise.

Thanks, Gary Higgins, Always Sunny, DF41, HB, So-Cal
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