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How critical is shaft to engine alignment?

Farlander

Member II
Hi All,

I have a 1970 35-2 with an Albin A2 diesel. The trans has a flange on the output shaft which mates with the prop shaft coupler. There's only about 3" of visible shaft before the shaft enters the stuffing box.

I recently had the boat out of the water and replaced the cutlass bearing. With bearing removed, the prop shaft was up and to port in the strut.

After reassembly, I loosened the coupler and checked the alignment. I verified the coupler angle (vertical tilt) was slightly off - about 1/64" gap between the top halves of the coupler. with the bottom faces touching.

When trying to adjust the engine mounts, the studs spun inside the rubber, thus nullifying the possibility of any adjustment.

Question: How serious of a condition is this? The engine doesn't vibrate too much (it's the same whether in neutral or in drive) and the prop shaft flange spun true when checked independent of the trans.

Has anyone experienced a prop shaft or coupler failure? There was moderate corrosion on the shaft coupler. I'm wondering how concerned I need to be and whether to invest in the engine mounts or wait for the next haul out to address. I've motored twice (about 1 hr) including high revs and have had no problems.

Thanks!
 
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Leslie Newman

Guest
I am very particular about the mechanical stuff. Aligning the shaft is usually done with a feeler gauge, so if you can see visibly 1/64", to me that seems like a lot.

When you say the engine mount studs spun in the rubber, can you clamp vise grips on the rod to hold it as you move the nuts. The alignment is moving two nuts (top and bottom nut), so you just need to stop the stud from moving so you can adjust the nuts, correct? I would do what it takes to make sure the alignment is correct as you can get it. Or, lock two nuts together at the top of the stud (if there is room) and then use that with a wrench to hold the stud.
 
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Frank Langer

1984 Ericson 30+, Nanaimo, BC
Hi,
I agree with Leslie that this merits a bit more attention. The Ericson manuals indicate quite strongly that alignment should be within .002 of an inch (that's thousands), about the thickness of one sheet of paper. Other sites are a bit more flexible, but the rule of thumb seems to be one thousands of an inch for every inch diameter of the shaft coupling. That is not easy to achieve, and having done it several times, it can take a while and be frustrating. But one time I thought mine was close enough, even though the shaft was a bit stiffer and harder to turn than it usually is, so I ignored it. Not long after, the transmission started to slip for no apparent reason. The transmission is not very old and I had changed fluid not that long ago, so it should be fine. After some head scratching, I decided to check the engine alignment with the gauges--it was quite a bit out. I redid the alignment and got it to .002 after several hours of hard work. After that, the shaft turned freely, no more transmission slipping, so I learned my lesson. Just my experience....
Frank
 
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Parrothead

Member III
To duplicate the alignment of the factory installation the shaft must be centered in both the strut and shaft log which are in fixed positions, then the adjustment can be performed accurately. This eliminates shaft position influence by the stuffing box and deflection from shaft weight.
 
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Farlander

Member II
Here is a picture of the mount and the shaft coupler. I understand the concept of having the shaft and the engine aligned with in .002", but I'm pretty sure my engine vibrates at least 1/4" from side to side just from idling, just saying.

Has anyone ever had a shaft bend or break?

Has anyone replaced this type of stud-in-rubber engine mounts with the engine in the boat?

Thanks,

20181230_174936.jpg
20190216_113542.jpg
 

Afrakes

Sustaining Member
Mounts

It's probably well past the time to replace all of the mounts. Believe me, you will have problems getting the old mounts off the brackets. Very little room to get a clear swing on a wrench and usually something is in the way that prevents you from using a breaker bar and socket. Cutting them off remains the only option. The easier way to do that is to take the weight off of the mounts and un-bolt the brackets from the engine and remove the entire assembly. Those bolts are going to come out much easier than the mounts themselves. With the assembly out you can cut off the old mounts and install the new ones. That way you can do one at a time and not have to hoist the engine too much. Everything depends on how much working room you have around the engine. If any of the brackets are part of the engine or transmission casting then raising the engine is the way you will have to go.
 
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tenders

Innocent Bystander
I haven’t done this myself yet but I’ve been told that a good way of getting upward pressure on the engine to loosen the mounts is to stuff an uninflated basketball under the engine...and then inflate it.
 
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Leslie Newman

Guest
Appears you probably can't fit a drip-less stuffing box due to space. They really help to keep things clean back there, no water flinging around if you don't have the packing adjusted correct. Mine has the PYI PSS seal and it does the job. This season, few weeks ago, I replaced the bellow per their recommendation of every six years. Other than that I don't have to do anything to it except keep a check on things.

Replacing the bellow (installing maintenance kit from PYI)
20190118_094831.jpg

New bellow, O rings and clamps in place.
20190118_111738.jpg
 

Kevin A Wright

Member III
If the studs are turning in the rubber, it's time to replace the engine mounts. And if you are doing that replace all of them. You might find after you do that that your engine vibration is reduced significantly. And a lot cheaper than new transmissions or worse. Other tip is when you go to align the shaft and engine, you should be in the water, not on the hard. Get it close while on the hard is OK, but do a final adjustment after she's been in the water a while. Even our great TAG ladies have a certain amount of flex in the hull and it doesn't take much to throw off an alignment.

Kevin Wright
E35 Hydro Therapy
 

ChrisS

Member III
Just replaced my mounts last summer

I broke a mount on the way back from Santa Cruz last summer. Replaced all four mounts under my A4. To get access to the port side of the engine, I cut an access hatch via the quarter berth. It’s a two person job.
 

JPS27

Member III
inflating basketball was the way to go for me

Somewhere on this site I posted about my challenges with alignment and mounts last year. One of the bright spots was trying the b-ball routine., I deflated a regulation (and good quality leather) basketball and it would magically lift the engine so I could fiddle with shimming and alignment etc. I was very careful for fear of failure. I worked with another buddy and we also placed blocks of wood to "catch" the engine in case anything slipped. Never had a problem. Shove the deflated ball under the engine with the valve pointing toward you (might as well shove it under while it's attached to the needle). Then start pumping. Doesn't take much air really.
 

Farlander

Member II
I have the Albin A2 diesel which is mounted aft of the companionway, access isn't great but there are 4 mounts and they are all visible. After reading the article I'm inclined to leave it alone since I'm kind of burned out on boat projects (spent every free hour for a month just on the sliding hatch) BUT ending up on the rocks, wall, or pier due to prop shaft failure at the wrong time would be disheartening...
 

Farlander

Member II
Mount Replacement Decision Made

A friend and I ran the engine at the dock in forward, reverse, throttled up, throttled down, idled in neutral, and observed the engine movements. First it was noticed that at idle in neutral, the engine vibrates on its own side to side about 1/4 of an inch at the top of the engine. I didn't have a dial indicator to confirm the exact amount of movement but I'll try and link to a video below. The second thing we noticed was the engine vibration did not change at all with forward or reverse engaged, giving me comfort that any lateral torque that may be exerted on the shaft is not enough to cause a noticeable vibration above what the engine generates on it's own.

My friend's boat, a Colombia 36, has a Yanmar diesel with brand new engine mounts of the same type and size. His engine also vibrated approximately the same as mine with much older mounts.

Conclusion, .004" of alignment is not going to happen on this boat with these engine mounts, and I'm ok with it.
'
 
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Leslie Newman

Guest
Conclusion, .004" of alignment is not going to happen on this boat with these engine mounts, and I'm ok with it.
'

You're probably correct. I have always been very anal regarding that alignment, but just recently I found this article - https://www.yachtsurvey.com/Alignment2.htm
I do like reading this surveyor's articles. He lays it out there. I still do try to obtain as good a coupling alignment as I can get, but I also do inspect how the shaft and cutlass are doing.
I figure you get everything as close as you can get it and that is all you can do. If whatever boat you own is poorly designed then you have factors out of your control. I'm on my fifth boat (if you count large sailboats) and I seem to always learn stuff that will be factored in on the next boat purchase. I'm all about the systems and construction, the hull design, is she sea kindly. A fellow at the boat yard the other day said that my boat was just plain sexy. He was admiring the hull shape, as I often do.
 

Parrothead

Member III
Working with a good friend on his E26-2 with a Yanmar 1GM, we made our best effort aligning the engine. One resultant effect was stuffing box adjustment. Before alignment it could not be adjusted to meet the goals of zero drips at rest and a proper drip ratio under way. Following careful alignment the goal was easily achieved. It may seem like a little thing but the difference was noticeable.

Consider that there is no downside to careful alignment.
 
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