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Old 18-02-2018, 11:51   #16
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

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Originally Posted by Mirror16 View Post
I have a new prop shaft and couplings on my Bristol 45.5 and it's visibly misaligned with the engine/gearbox. The boat is currently out of water, sitting on its keel, propped up in the usual manner. I am being advised that this realignment should be done after the boat has been back in the water for a few days, but for schedule reasons I would much prefer it's done now. I cannot imagine that engine to prop shaft alignment would change very much on a solid lump of a boat like this between it being on the hard and in the water. Comments?


No it doesn't move much. But when alignment is measured in thous it moves a lot.
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Old 18-02-2018, 11:56   #17
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

Ideally, in the water. However, if that isn't feasible, do the best you can and then observe it when you first run it. Regardless, it'd be prudent to inspect it regularly.
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Old 18-02-2018, 12:08   #18
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

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Originally Posted by CarlF View Post
I would align now. Your boat has a short shaft and no strut - not much to worry about. And it's worrisome that the new shaft is visibly out of alignment. Something may need to be fixed after they try to align and fail.

But when a shaft is changed, it's no uncommon to have to do an alignment more than once to get it right. You can run fine on a less than perfect alignment until it's convenient to tweak it.

More important, find a really good guy to do the alignment. This is as much art as science. It wouldn't hurt to do a rough alignment, then run the engine in gear on the hard for a few minutes to settle things in, then finish the alignment. They can just run a hose into the strainer with the lid off for cooling water. Did you replace the cutlass bearing too?
Align within .003 now on the hard. Recheck after launch, max .003 within 50 hrs of run time.
It will change a bit, rechecks should be done periodically.
If you can turn the shaft with 1 hand, easily it's very close.
Cheers,
SV Cloud Duster
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Old 18-02-2018, 12:45   #19
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

Here’s an easy way to check your alignment. Download a protractor app on your cell phone. Use it to compare your mounting angle on the shaft with some parrellel surface on your motor or riser. When they are within 1/2 degree in the vertical plane, you will be very close.

Doesn’t necessary work at the 3 and 9 o’clock positions, but it saves a lot of head banging otherwise.

Btw, all boats develop twist in the hull when laid up on the hard. For example, even cast iron metal lathe beds twist measurably over time when set up on an uneven surface. So it would be a good idea to check your alignment a week or so after relaunching, after your hull has “relaxed” into its natural shape.

The main risk being out of alignment, according to the marine transmission rebuilder I talked to, is the bearings and seals in the reverse gear will go bad, in very short order- often less than 100 hours - if the shaft and/ or flange is misaligned with the tranny.

So definitely spend some time to learn how to adjust your engine mounts.

Btw, with visible misalignment, the solution is to move the engine on the bed. Not mess around trying to re bed the cutlass bearing. I ended up making new engine mounts one time, to accommodate a new cutlass bearing. But it had to be done as the old mount was never done correctly during an engine replacement. the reverse gear eventually failed. Necessitating replacing everything, and rebuilding the transmission.

As I think about now, I’ll bet the hull was twisted so badly when the motor and new engine mounts were installed on the hard, that it could never be properly aligned after sitting in the water.
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Old 18-02-2018, 13:00   #20
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

i guess I've heard everything? An app. replacing a dial indicator and feeler gauges. Sorry! I couldn't help it.
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Old 18-02-2018, 13:47   #21
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

Quote:
Originally Posted by Glenn.Brooks View Post
Here’s an easy way to check your alignment. Download a protractor app on your cell phone. Use it to compare your mounting angle on the shaft with some parrellel surface on your motor or riser. When they are within 1/2 degree in the vertical plane, you will be very close.

Doesn’t necessary work at the 3 and 9 o’clock positions, but it saves a lot of head banging otherwise.

Btw, all boats develop twist in the hull when laid up on the hard. For example, even cast iron metal lathe beds twist measurably over time when set up on an uneven surface. So it would be a good idea to check your alignment a week or so after relaunching, after your hull has “relaxed” into its natural shape.

The main risk being out of alignment, according to the marine transmission rebuilder I talked to, is the bearings and seals in the reverse gear will go bad, in very short order- often less than 100 hours - if the shaft and/ or flange is misaligned with the tranny.

So definitely spend some time to learn how to adjust your engine mounts.

Btw, with visible misalignment, the solution is to move the engine on the bed. Not mess around trying to re bed the cutlass bearing. I ended up making new engine mounts one time, to accommodate a new cutlass bearing. But it had to be done as the old mount was never done correctly during an engine replacement. the reverse gear eventually failed. Necessitating replacing everything, and rebuilding the transmission.

As I think about now, I’ll bet the hull was twisted so badly when the motor and new engine mounts were installed on the hard, that it could never be properly aligned after sitting in the water.
Always align the engine to the shaft, never pressure the shaft to fit the engine coupling.
After running in gear for alwhile, in the water, check the packing gland temp. With an infrared thermometer, or even by hand it shouldn't be warm to the touch.
Glands and even the gland to shaft log hose could be pressuring the shaft one way or another giving false measurments to the coupling faces, even dirt, or a burr on the face.
Check it and do it correctly, you'll save a lot of headaches and downtime.
Cheers,
SV Cloud Duster
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Old 18-02-2018, 13:49   #22
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

It should be floating with the rigging all tuned. These factors do affect alignment.
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Old 18-02-2018, 13:53   #23
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

Cadence,

Haha. I couldn’t believe it myself when I tried it. But, my mechanics - yes plural, (the shop sent two guys over several days, to no avail) and I, tried everything to get the alignment right. Don’t know why it wouldn’t work.

Anyway the app was surprisingly accurate. I set the angle and the flange just slipped into place. A “two finger” slip fit. Down around a thou in clearance.

Btw, I like your DTI approach. I do this all the time with four jaw chucks in my machine shop. Although, Lot better mounting surfaces on my lathes! Plus, usually not standing on my head to read the dial.
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Old 18-02-2018, 14:33   #24
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

Yes Dials are the go.

It's 2 actually, each attached to one shaft reading on the other shaft.

Yes standing on head to read them is all part of our boating fun, eh.

Apps, try this one - https://shaftalignment.net/apps/ But it is only a calculator still need Dials to get the measurements. It is great and will give you exact adjustment measurements. However as apposed to industrial motors that are typically shimmed, with boat motors we dont need to know what measurement to move our mount nuts. We just move them till the Dials read 0.

PS Not that I have any interest in these guys but their Shaft alignment vids are great if you want to learn about shaft alignment.



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Old 18-02-2018, 15:15   #25
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

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Originally Posted by Glenn.Brooks View Post
Cadence,

Haha. I couldn’t believe it myself when I tried it. But, my mechanics - yes plural, (the shop sent two guys over several days, to no avail) and I, tried everything to get the alignment right. Don’t know why it wouldn’t work.

Anyway the app was surprisingly accurate. I set the angle and the flange just slipped into place. A “two finger” slip fit. Down around a thou in clearance.

Btw, I like your DTI approach. I do this all the time with four jaw chucks in my machine shop. Although, Lot better mounting surfaces on my lathes! Plus, usually not standing on my head to read the dial.
I'm glad it worked. I'm old and stupid and just can't envision it.
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Old 18-02-2018, 18:21   #26
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

All above comments are very good... however, I just installed a new engine in a boat and I new alignment would have to be done. While the engine was out I did a test on bed mounts to find out that one engine mount block was sitting on a rotten member of the fiberglass. We had to cut out the rot and laminate a new frame and glassed a new framing. We the did the final installation and aligned it on the hard. We did recheck floating and all was good. Last year I did an alignment on a steel boat. There was very loud noise and vibration. The motors were twin Isuzu 370 hp motors. We shimmed the motor mounts and realigned the coupling using only feeler gauges and steel shims and the results were very good. We recently did both prop shafts on this boat and rechecked the alignment on the final installation and all was good... no need to re-align. My two cents worth... Roger.
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Old 18-02-2018, 23:50   #27
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

I can only tell you our experience - we lost a dripless shaft bearing in Colombia. We hauled painted and had a mechanic come and replace it. He insisted that we do not even start the engine once it was in the water until he did a final adjustment and check -
We only do the final adjust in the water but that is just us - others many do other things but that is our opinion for what it is worth
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Old 19-02-2018, 04:41   #28
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

I used to align large lasers and it's much the same with engines and prop shafts. The supports for the engine are inboard of the shaft coupling. When you make an adjustment to the shaft end in one direction, keep going an extra half distance in that same direction. But bring the opposite engine end into proper square and alignment. Then back for shaft end distance and one half, opposite end just right.

You'll get there twice as fast.
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Old 19-02-2018, 05:25   #29
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

I would recheck after the boat is in the water
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Old 19-02-2018, 12:26   #30
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Re: Engine to Prop Shaft Alignment with boat out of water vs floating?

All boats flex - just some more than others. Ideally the weight should not be all on the keel. It should be evenly distributed to all supports and the keel for best results on land. but judging that is hard to do - but not just balanced on keel with lateral supports. Then align it on land and check it once in the water.
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