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Old 19-12-2007, 13:21   #1
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Shaft Seal - This Could Get Ugly...

OK, so it's about time to tackle the newest problem that's come up. Looking for some tips from y'all before I dive in....

Clue #1: Previous owner had told me a story about how his bellows-type shaft seal started leaking while underway - and he couldn't get it to stop. So he had it replaced with a new type Lasdrop carbon seal unit. Purchase survey said the running gear was fine (don't they all say that?)

Clue #2: PO says the guy came down and installed the new seal while they were still waterborne. Hmmm.... the Lasdrop instructions say that's a no-no...

Clue #3: When the shaft is turning I can visibly see runout at low RPM. Seems to settle out at higher RPMs but is still there. I wonder if that's more than just normal thrust torque I'm seeing... Does not seem to be more or less than the way it was when we bought the boat.

So fast forward about 100 hrs of motoring later. I take the boat to haul out, get her a haircut and then splash again. Quick 1-day round trip.

Clue #4: While she's hanging in the slings, I turn the prop by hand and feel a resistance through one portion of the circle - seems to be about 30 degrees of rotation where things bind up a bit. Doesn't seem real bad but enough for me to notice.

So, splash back in and boy she moves faster through the water now with the clean hull! But yikes, the shaft seal leaks.

Clue #5: Seal leaks LOTS when under load. Bilge pump keeps up just fine but I really don't like water coming into the people tank like that. While at low / no RPM all is dry (thankfully).

Clue #6: No abnormal vibration heard / felt after the haul-out. All seems the same except for the leaking shaft seal.

Clue #7: Come to think of it, the engine used to spin happily up to 3200 RPM under load. Now I get black smoke and increasing temp around 2200 RPM. She will not go past 2300.... this can't be good. However, prior to the haul-out this was also true.

So now it's time to repaint the bottom and address the seal issue. As I've thought about it, the scenarios could be (from least to most severe):

a) Since the new seal was installed while waterborne, I just need to readjust it properly while out of the water this time.

b) I need to re-align the shaft and then readjust the seal. If the resistance is gone when I turn the prop after that, then all is fine.

c) The new seal is toast and will have to be replaced. Nothing else really wrong. Will have to break the coupling to replace the seal, then realign the shaft.

d) The motor mounts are sagging and will have to be replaced if I'm ever going to get the shaft run-out down to spec. (By the way - how much run-out is acceptable?)

e) The cutless bearing is shot and is the cause of misalignment / seal leakage.

f) The shaft is bent / warped and it trashed the cutless bearing so bring a big check book....

Being the newbie that I am, I've never done an alignment before and don't have the gages or mounts I'd need. Will probably hire that done but wouldn't mind doing it myself.

Any thoughts / tips / probable causes you folks can share? As always, many thanks in advance for your replies!

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Old 19-12-2007, 13:47   #2
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Aloha Mark,

Let's just hope it is engine/shaft alignment.

"Being the newbie that I am, I've never done an alignment before and don't have the gages or mounts I'd need. Will probably hire that done but wouldn't mind doing it myself."

It isn't rocket science and all you need are the necessary wrenches and a feeler gauge. It takes time to realign a shaft properly but a novice can do it just fine. Each engine mount/shaft coupling/shaft log combination has a difference tolerance recommendation. Get it as absolutely perfect as possible.

Did you notice play in the prop shaft when you grabbed the prop and worked it in it's circle? Take the prop and wiggle it back and forth up and down, side to side. There shouldn't be any noticeable play and especially no clunk sound which ever way you shake it. You might not need a new cutlass bearing but it is good to check each time you haul out.

Good luck.

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Old 19-12-2007, 13:52   #3
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i put lasdrop sys. in our boat 2 yrs ago. had to do cutlass bearing, straighten out strut (bent in previous haulout p/o) then new coulping and shaft and stuffing box(shaft and stuffing box ruined because strut was bent). anyway had to realign after in water i think it was +- 2 thousands of and inch. no probs now not that i had any before other than slop in the cutlass bearing, and i could not stop old stuffing box from leaking even after new packing material. the one thing i did read about the dripless sys. is you have to pull the bellows back and let water get on the seal surface if boat hasn't been used for a while (over two or three weeks i think) because the seal area dries out and then you overheat the mating surfaces causing the (i think it's grafite)ring to disintergrate.
wasn't a major job just tedious and didn't have much room to work in GulfStar 37 enter shaft area thru cockpit lockers. can you say contortion artist

good luck
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Old 19-12-2007, 14:00   #4
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If you can't get to WOT something is bound up somewhere. Your are going to have to go through the drivetrain to find and fix the problem. Not much of a Christmas present but you're are going to have to call the mechanic.
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Old 19-12-2007, 14:07   #5
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This sounds like a good time to replace that cutlass bearing anyway. It sounds like that may be the sourse of resistance in your engine. I hope that the bearing isn't so far gone that it has damaged the shaft.

Some cutlass bearings are made of rubber composites. The composite can come apart and you won't feel any lateral movement in the shaft but it may be hard to turn, once it gets warm (from friction). Those are very difficult to diagnose but are very obvious once you get it out.

I'd replace the bearing and unbolt the prop-coupling from the gear box (which you will have to do anyway). Check the shaft run-out with a dial-indicator several places along the shaft, with the new bearing in. :
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Before bolting up the coupling, check the flange, all the way around with a feeler gauge. You should have no more than .004" diference from one sde to the other.

To make adjustments, you can loosen the engine mounts and move it side to side. If it needs to be raised in the front or rear, you can use shims. I wouldn't replace the mounts unless they are broken.

Torque the mounts down after achieving the correct tolerence, then check it again before final bolting of the flange.

BTW....don't forget to make sure that the flange is running true (dial-indicator) before starting any adjustments.
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Old 19-12-2007, 14:11   #6
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Something is definitely wrong here. The loss of RPM and black smoke is telling - something is seriously loading the engine now that wasn't when you were getting 3200 RPM.

I would check the engine mounts and alignment first. The specs I have seen for runout are .002-.008". I would not think you would be able to observe that much runout visually. If the alignment is way out (and has been getting progressively worse due to a bad/loose mount) then this could be the cause of the binding and black smoke. It also could be that the shaft is rubbing on the shaft log causing that binding you observed. So make sure that the shaft is centered in the log during the alignment process.

The shaft seal performance seems consistent with poor alignment. At rest, the seal can adjust to the shaft position and seal or seat. At high RPM, it cannot track or "keep up" with the dancing shaft and the water comes in.

Check that cutlass bearing too. With the boat hauled, you should feel very little/no side play in the bearing. I don't know how to detect a bent shaft short of mounting a dial caliper along its length and checking.

There are others on this board that probably know more than I. Maybe they have some thoughts too.

Dave
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Old 19-12-2007, 14:21   #7
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The first thing you should do is get those motor mounts replaced/stabilized. Until you get those mounts fixed the shaft will never stay aligned.
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Old 19-12-2007, 20:33   #8
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Friction creates heat. Go motor around for a while under load and then shut down ond go feel the stuff you can reach. I'm surprised something dragging that much horsepower isn't creating smoke.

As far as the fix - I am a systems guy. Start at the engine mounts and work it all systematically all the way to the prop. Then you'll sleep well at night.
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Old 20-12-2007, 21:06   #9
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I don't quite follow what you mean about sagging motor mounts.

Do you have a fixed or adjustable pitch prop?

Engine?

Keep us posted...we'll help you out.
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Old 21-12-2007, 06:55   #10
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Quote:
Originally Posted by Chief Engineer View Post
I don't quite follow what you mean about sagging motor mounts.
As they age I understand that the rubber starts to distort / sag / compress and that affects alignment.

Quote:
Originally Posted by Chief Engineer View Post
Do you have a fixed or adjustable pitch prop?
Fixed 3-blade prop.

Quote:
Originally Posted by Chief Engineer View Post
Engine?
Yanmar 4JH2-DTE.

This may be a stupid question... but if I have to pull the shaft, in order to clear the rudder will I need to first pull the cutless bearing so that I can angle the shaft past the rudder?

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Old 21-12-2007, 09:41   #11
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Quote:
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As they age I understand that the rubber starts to distort / sag / compress and that affects alignment.



Fixed 3-blade prop.



Yanmar 4JH2-DTE.

This may be a stupid question... but if I have to pull the shaft, in order to clear the rudder will I need to first pull the cutless bearing so that I can angle the shaft past the rudder?

I'm not real familiar with the Endeavour 52. I am assuming that she is either a full or modified full keel. Usually, the rudder has a "C" shaped cut-away in the rudder for prop clearance.

If you remove the prop, you should be able to pull the shaft all the way out to replace the bearing by turning the rudder hard to one side. This is a good time to inspect and clean the shaft up real good.

As far as the mounts go, new mounts may have a small amount of "Settleing" after she is new which may require some re-alignment. However, it is rare that the mounts need to be replaced unless they have been oil soaked or broken.

EDIT:

I just found this pic....All bets are off. I'm not familiar with removing the shaft on this set-up. I'm sure that someone else is. Quite frankly, I'm a little shocked at the diameter of that prop shaft. It looks awfully small in this picture (which could be deceiving).

Have you ever gotten a line wrapped around the prop? That strut looks very vulnerable.

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Old 21-12-2007, 12:17   #12
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There are some variations in the shafting arrangement apparently. Here's mine when first hauled last year - before clean-up (yuck!) I have a single strut supporting the 1.5" shaft. Heavy steel backing plate supports it under the aft berth.

No I've never wrapped a line on the prop - knock on wood...

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Old 21-12-2007, 12:32   #13
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Mark, is this Lastdrop system a graphite ring rotating against a steel ring, or something similar? I know, technically they are the cat's meow, but I've seen them fail repeatedly in car airconditioning compressors, and more recently in a dishwasher motor shaft seal, $350 repair thanks to what can only be an assembly problem, the faces of the graphite and steel all look "perfect" every time, they just fail.

So I just don't trust them. When they're big installations backed up with engineers and maintenance programs and positive pressure alarms, yeah, great. I just don't trust the little ones at all.

Personally, I'd pull it and put in a conventional shaft seal with a GoreTex or teflon-based "permanent" packing. When those "fail", they just need a little tightening.

Engine mounts, like all rubber parts, degrade as they age. SOme amkers use urethanes or other more expensive compounds that are supposed to perform (and age) better, needless to say they cost more. After 5-10 years under the best of conditions, rubber will harden up and transmit more vibration to the hull. Might or might not change the alignment--but after five years it would be time to check that anyway! Moving parts do, after all, sometimes move.[g]

As long as you've got this mystery list, and you're going to be hauling anyway, I'd do two things: Call the maker, ask them if that installation, or bad alignment, could ruin the seal surfaces. I suspect so. And then while you are hauled, either check everything out yourself, or have someone competent (hahaha, just try to find one) do all that for you, so all the bases are covered rather than having to finger-point and say "Yeah, well, it was this other thing you didn't do...." afterwards.

And my apologies to your wallet, for making such a suggestion, but sometimes...it just pays to bite the bullet, and make sure the whole thing is 100% all the way. Then you can just go sailing, while trying to figure out how to pay back the bank.[g]
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Old 21-12-2007, 13:33   #14
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Pulling the shaft is a problem on my boat as well. It's easier for me to drop the rudder than remove the strut. I've set up a block system on the backstay in which I can lower and raise the rudder.

As for the cutlass bearing, I've made a special tool for extracting it with the shaft in place, when due.
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Old 21-12-2007, 14:24   #15
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Well... this is not giving me that warm fuzzy feeling...

I sure hope I have enough clearance so that I don't have to drop the rudder... no seepage at all from the rudder stock, turns easily, etc. I'd like to leave well enough alone for a change...

Can't wait to get started on this one...

OK all together now, "I LIKE boats... I really really LIKE boats..."

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