shaft alignment - SailNet Community
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post #1 of 7 Old 02-18-2014 Thread Starter
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shaft alignment

My H-34 has shaft vibrations. I'm installing a new prop and checking for shaft bend. The strut is bent. When I free up the strut, how do I know when I've got it realigned right? Any help would be appreciated.
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post #2 of 7 Old 02-18-2014
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Re: shaft alignment

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Originally Posted by jfitzgerald View Post
My H-34 has shaft vibrations. I'm installing a new prop and checking for shaft bend. The strut is bent. When I free up the strut, how do I know when I've got it realigned right? Any help would be appreciated.
Jim F
You cannot align it when it is bent. You can try to have it straightened, otherwise replaced.
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post #3 of 7 Old 02-18-2014
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Re: shaft alignment

After correcting the strut you will have to realign the shaft at the transmission coupling. This involves separating it slightly and rotating it while checking the gap with a feeler gauge. The gap has to be very precise - less than 0.007" runout through a full rotation - your specific engine & trans combo will have a spec for this.

With any luck the runout will be vertical and can be adjusted with the nuts on your engine mounts. If it is horizontal you have to loosen the mounts and pry the engine sideways - this can take many tries as pry-bars are not nearly as "fine" an adjustment as the threads on the mount studs.

The fact that your strut is bent means a fairly high likelihood that you will need some horizontal adjustment.

Do it initially before launch in case something nasty pops up but you will have to do the final realign in the water because the boat will flex somewhat after launch.
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post #4 of 7 Old 02-18-2014
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Re: shaft alignment

GREETINGS EARTHLINGS Try to get hold of a dail indicator this will help to find the stressed area and bends on the shaft and feeler gauges help when lining up the engine HOPE THIS HELPS AS ALWAYS GO SAVE
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post #5 of 7 Old 02-18-2014
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Re: shaft alignment

As mentioned above you cannot do anything until you deal with the bent strut.
However, installing the strut correctly is not something you should attempt yourself. It isn't just a case of rebolting it in place. It must be perfectly placed (shimmed or holes redrilled if necessary) or you will never be able to align the shaft properly. I highly recommend you have a yard professional do that job.
The alignment itself is not difficult as long as the engine mount bolts are free and easily turned. I can't remember the exact number of deviation from perfect that is acceptable, but it is in the thousandths, so be prepared for some very tedious work with a feeler gauge.

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post #6 of 7 Old 02-19-2014
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Re: shaft alignment

I took a heavy piece of steel, set in the hull, and mounted a magnetic base dial indicator to it. I found that the ears on the transmission did not have a true for & aft run out. I had to build spacers to compensate for that. I don't remember but I think the variance between ears was about .007. Everything is nice and smooth now.
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post #7 of 7 Old 03-04-2014
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Re: shaft alignment

Adjusting a heavier engine side ways can be easier if you weld up a movable C clamp from short bits of angle iron that hangs onto the engine bed and straddles the mount. Half inch nuts welded to the top face take the bolts that will push the base (one at a time) into position .It may take a keen eye on the strut cutlass before starting moving the engine around
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