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Old 09-10-2014, 15:59   #31
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Re: Name this prop noise...

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Originally Posted by delmarrey View Post
Then I'd be looking at the prop.

While its out of the water run the system with water running over the cutless bearing and into stern tube (stuffing box) and watch the shaft.

If the noise is that far back I'd suspect the prop being out of balance, loose or even bent where it presses on.
My dumb guess would be the prop also. Maybe the rebuild wasn't good? If it a harmonic of speed and that prevalent.
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Old 09-10-2014, 18:20   #32
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Re: Name this prop noise...

I come back to the initial statement of 0.04" of misalignment. that right there is more than enough to cause exactly what you are describing. order of magnitude too high.

good luck!
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Old 09-10-2014, 18:24   #33
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Re: Name this prop noise...

Thanks for the info and the help. We are going to keep the RPMs below 50% for the times we are motoring and stay under sail as much of the time as possible. Once were back on the hard the engine mounts are coming out and we will be inspecting the stern tube. I'll update this thread once I have more info so keep tuned!


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Old 09-10-2014, 18:41   #34
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Re: Name this prop noise...

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Originally Posted by AndDavRos View Post
Thanks for the info and the help. We are going to keep the RPMs below 50% for the times we are motoring and stay under sail as much of the time as possible. Once were back on the hard the engine mounts are coming out and we will be inspecting the stern tube. I'll update this thread once I have more info so keep tuned!


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Just for S&Gs can you feel it on the engine? I would think, if the .04 was the problem you would?
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Old 09-10-2014, 18:42   #35
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Re: Name this prop noise...

We didn't see or feel any significant movement in the engine, but I'll check the next time we run everything up this weekend.


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Old 09-10-2014, 18:53   #36
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Re: Name this prop noise...

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We didn't see or feel any significant movement in the engine, but I'll check the next time we run everything up this weekend.


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Thought I'd ask. Replacing engine mounts sounds expensive. It might be a if it is a wheel or shaft.
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Old 09-10-2014, 20:58   #37
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Re: Name this prop noise...

Just found this thread. Heres my left wing suggestions.
1.Did you mention the make of engine, has it got a balance shaft in there for harmonic purposes that is now malfunctioning?
2. Is it a 4 blade propeller that is giving you the double harmonic by passing thru the deadwood area of your long keel? has somehow the axial clearance of the propshaft to keel been altered.
3. How many couplings between your gearbox and propeller are there any Universal couplings or soft couplings?.
Cheers
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Old 14-11-2014, 10:54   #38
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Re: Name this prop noise...

It's been a while since I updated this thread so I thought I would follow up with folks. The engine and transmission are not the issue. It looks to be a combination of factors. Our alignment is off slightly and there is a very small clearance in the stern tube with an unsupported length of a little over 4'. The sound we were hearing is (most likely) the prop shaft coming into contact with the tube (which has a lot of rust scaling). We are going to pull the prop and shaft and hone the stern tube and have the engine mounts machined to give us the clearance required to bring the engine into alignment. The trick will be testing the setup before we put in in the spring. I'll update this thread as we find out more details once we pull the prop and shaft.


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Old 11-01-2015, 21:40   #39
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Re: Name this prop noise...

Uh, .003 is acceptable. Not .015, that's way out.


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Old 11-01-2015, 21:44   #40
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Re: Name this prop noise...

Did you say 4' of unsupported shaft length? if so, you'll need to rig up something to support the shaft during alignment, that much "hang" bends the shaft enough to make alignment very difficult.


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