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Old 06-28-2017, 07:11 PM   #21
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Originally Posted by Ski in NC View Post
There is runout visible. Put dial indicator on shaft about a foot aft of coupling and roll it by hand. If zero or close, then likely prop. If significant, like over 0.020", then loosen coupling bolts one turn each and repeat. If runout decreases significantly, there is runout in either shaft coupling flange or tranny flange. If runout still there, shaft likely bent.

Above is an easy check that will narrow the list of possibilities. Can be done in under an hour.
Sounds simple enough although I don't know what the "dial indicator" looks like, or where to purchase one. And when you say roll it by hand, am I rolling the dial, or the shaft? Obviously I am not very far along the learning curve here. Might have to just pay a mechanic to do this. That said, once I "see" something done, I am good at replicating!

That said, I do plan on watching the mechanic service my engines in the hope that I can save some labor next time around.
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Old 06-28-2017, 07:24 PM   #22
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Sounds simple enough although I don't know what the "dial indicator" looks like, or where to purchase one. And when you say roll it by hand, am I rolling the dial, or the shaft? Obviously I am not very far along the learning curve here. Might have to just pay a mechanic to do this. That said, once I "see" something done, I am good at replicating!

That said, I do plan on watching the mechanic service my engines in the hope that I can save some labor next time around.


Many many years ago when I was "on the tools" Id treble my hourly rate when I had a audience and go twice as slow .It made up for next time
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Old 06-28-2017, 07:36 PM   #23
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Many many years ago when I was "on the tools" Id treble my hourly rate when I had a audience and go twice as slow .It made up for next time


Glad I am paying a flat rate then!
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Old 06-28-2017, 08:00 PM   #24
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Originally Posted by Ski in NC View Post
There is runout visible. Put dial indicator on shaft about a foot aft of coupling and roll it by hand. If zero or close, then likely prop. If significant, like over 0.020", then loosen coupling bolts one turn each and repeat. If runout decreases significantly, there is runout in either shaft coupling flange or tranny flange. If runout still there, shaft likely bent.

Above is an easy check that will narrow the list of possibilities. Can be done in under an hour.
Sounds like a good plan to limit possibilities that may be cause of this situation.

Damn... boats and all their possibilities! Gott luv em; cause if we didn't we'd dump em. These gals we call "boat" really do have a magical attraction/draw on our inner selves.
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Old 06-28-2017, 10:52 PM   #25
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Quote:
Originally Posted by Ski in NC View Post
There is runout visible. Put dial indicator on shaft about a foot aft of coupling and roll it by hand. If zero or close, then likely prop. If significant, like over 0.020", then loosen coupling bolts one turn each and repeat. If runout decreases significantly, there is runout in either shaft coupling flange or tranny flange. If runout still there, shaft likely bent.

Above is an easy check that will narrow the list of possibilities. Can be done in under an hour.
Boy!!! it sure is nice to have Ski in NC on this forum
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Old 06-28-2017, 11:16 PM   #26
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Originally Posted by Ski in NC View Post
There is runout visible. Put dial indicator on shaft about a foot aft of coupling and roll it by hand. If zero or close, then likely prop. If significant, like over 0.020", then loosen coupling bolts one turn each and repeat. If runout decreases significantly, there is runout in either shaft coupling flange or tranny flange. If runout still there, shaft likely bent.

Above is an easy check that will narrow the list of possibilities. Can be done in under an hour.
I think I get it. Dial gauge like this:

So I need to make sure the gauge somehow stays exactly in place as I turn the shaft to check the runout. If no runout the assumption is everything is straight so likely the prop. If it is significant, I loosen the bolts that couple the transmission to the shaft to allow any tension being placed on the shaft to be released. Then test the shaft again and if it is the same runout, the assumption is that it isn't an alignment issue and is therefore a bent shaft.

Makes total sense! Thanks!
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Old 06-29-2017, 12:04 AM   #27
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Interesting article on engine/shaft/strut alignment.

Marine Engines : Drive System Alignment by David Pascoe, Marine Surveyor
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Old 06-29-2017, 12:54 AM   #28
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Interesting article on engine/shaft/strut alignment.

Marine Engines : Drive System Alignment by David Pascoe, Marine Surveyor
Pascoe does have some good articles. Hadn't read this one for quite a while. Much of what he says here is spot on. Makes me quite pleased that our shafts are 1.25" dia.
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Old 06-29-2017, 12:56 AM   #29
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Makes me quite pleased that our shafts are 1.25" dia.

Makes me think my boat is going to sink!
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Old 06-29-2017, 01:26 AM   #30
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Makes me think my boat is going to sink!
There are two types of concrete slabs on the ground - Thems that's cracked and thems that's gonna crack.

There are two types of boat's constantly kept in water - Thems that's sunk and thems that's gonna sink.

Moral of the story - Occasionally haul our boats and make sure they will stay afloat!

Happy "Boat-Float" Daze! - Art
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Old 06-29-2017, 01:31 AM   #31
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Good luck MB1969. I had a bent shaft(on the boat),replacing it cost. Let`s hope its something more easily fixed. Nice clean bilge you`ve got there.
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Old 06-30-2017, 01:03 AM   #32
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Slow motion video of my engine and shaft vibration

Quote:
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Good luck MB1969. I had a bent shaft(on the boat),replacing it cost. Let`s hope its something more easily fixed. Nice clean bilge you`ve got there.


Thanks Bruce!
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Old 06-30-2017, 08:52 AM   #33
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I had a mystery vibration on my boat a couple years back. After trying several fixes, the boatyard owner proclaimed it was a bent shaft and that if he was wrong, he'd pay for it himself. His theory proved false and I got a new shaft. I took the boat back without a fix, put on the correct prop zinc and solved the problem. Don't overlook the simple solution.
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Old 07-14-2017, 01:45 AM   #34
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Slow motion video of my engine and shaft vibration

Had my Volvos serviced a few days ago and he checked the alignment at the engine/shaft coupling and determined that I most likely have a bent shaft. Shaft was pulled at the yard yesterday and is at a prop and shaft shop. Estimate to straighten it was $770. For what it's worth, shaft is 50mm (2"). We'll see what they say. Didn't hear anything today but first step is that they put it on rollers and determine if it's bent or not, and if so, whether or not they can straighten it.
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Old 07-14-2017, 07:20 AM   #35
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Make sure that when on rollers, the coupling is fitted to the shaft and they indicate the face of the coupling too. A few thou out on the coupling face is magnified down the shaft line. Should be 0.000" TIR on face. (total indicated runout, meaning dial needle does not move. Really coupling face should be tested with shaft in a lathe as on rollers axial position is not fixed. But machine shop guys know this stuff.

Standard practice when doing shaft work is after shaft is straightened, shaft is put in a lathe, coupling fitted, and a skim cut made on the coupling face to make it absolutely true. If this is not done, you are getting a partial job. For $770, you don't want partial.
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Old 07-14-2017, 07:48 AM   #36
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What do you or anyone else feel bent the shaft... if it turns out to be bent? How's the prop and cutlass bearing?
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Old 07-14-2017, 07:55 AM   #37
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To Ski's point, you really need to go though testing the components before making a prognoses.

Many things can cause a vibration (as stated in other posts), best to find it before going the replacement route.
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Old 07-14-2017, 10:28 AM   #38
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What do you or anyone else feel bent the shaft... if it turns out to be bent? How's the prop and cutlass bearing?
Prior owner had a minor grounding incident that bent the props. The props were fixed at Osborne Propellers, a reputable shop up in Vancouver.

I guess they missed the fact that the shaft was impacted.

The shaft is currently at bayshipandyacht here in the Bay Area. They've been in business for 40 years and all the local yards use them for prop/shaft straightening. So I assume they know what they are doing. But I will definitely ask the questions you posed Ski in NC! Thanks!

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Old 07-14-2017, 10:31 AM   #39
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Originally Posted by Ski in NC View Post
Make sure that when on rollers, the coupling is fitted to the shaft and they indicate the face of the coupling too. A few thou out on the coupling face is magnified down the shaft line. Should be 0.000" TIR on face. (total indicated runout, meaning dial needle does not move. Really coupling face should be tested with shaft in a lathe as on rollers axial position is not fixed. But machine shop guys know this stuff.

Standard practice when doing shaft work is after shaft is straightened, shaft is put in a lathe, coupling fitted, and a skim cut made on the coupling face to make it absolutely true. If this is not done, you are getting a partial job. For $770, you don't want partial.
BTW, just looked at the quote. The line item says:
2" Propeller Shaft Straighten as needed fit & face coupling
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Old 07-14-2017, 02:32 PM   #40
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At first it looked like a bent shaft to me but looking more at the vid it looks like the whole engine, shaft and all is moving right and left .. sideways. But from the position of the camera vertical movement would be harder to detect.

Could be the wrong hardness of rubber in the mounts. Softer mounts at the wrong end. I put my aft mounts on the trans instead of the bellhousing to limit pitching and tail wagging. A bit like a car w longer wheelbase.

Some mounts aren't differential as they allow movement in all directions. Not ideal as engines move mostly from a power pluse happening or a power stroke happening. This accellerates the crankshaft and a compression stroke decelerates the shaft and flywheel. These radial forces causes the engine to rotate this way and then back. Heaving (straight up and down) movement (of the whole engine) is minimal as is pitching and yawing. Radial motion is the problem.

But the radial motion causes up and down heaving alternately from side to side. Right side going up as left side goes (moves) down. All of this boils down to the fact that mounts that move most easily up and down are great and most desirable. The almost exception to this is the mounts being required to deal w all of the thrust of the propeller in both directions.

Perhaps there is some not ideal element of engine installation applied here that needs to be changed. Understanding is the key to trouble shooting.

OP do you know of another boat w the same installation?
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