C-27 prop shaft

[deisher6]

Are  there any thoughts on engine shaft alignment and / or the following problem? 

How do you go about aligning the engine to the shaft?

I know that I have blogged on this topic before:  When I discovered that the shaft had backed out of the collar connecting it to the transmission after just having tied up at home dock.

When I last had the boat hauled I replaced the cutlass bearing, stuffing box packing, and had a new keyway milled into the bronze shaft, 180° out from the old keyway.  The existing keyway, that fits into the collar that is in turn bolted to the transmission, was badly distorted and chewed up.  When I reassembled the drive train I drilled dimples in the prop shaft for the set screws on the collar, and safety wired the set screws.

After some use the shaft blacked out of the collar.  This time I reassembled the shaft and collar and retightened the set screws using loctite.

Doing a pre cast off check of the stuffing box this week I saw the end of the keyway sticking out from the collar.  Again the shaft was loose and starting to back out of the collar.

I tightened everything up and went sailing. (The set screws were tight and had to be loosened to get the shaft back up in the collar.)

I am thinking that the problem is engine shaft alignment.  The vibration is causing the steel key to chew up the bronze shaft and keyway and eventually spitting it back out of the collar.  The shaft does not fit tightly in the collar, it easily slides into it.  On the other hand it does not appear to me to be overly loose.

I would appreciate any thoughts.

regards charlie

[Allure2sail]

Hi Charlie:
When you had the keyway recut was there did you notice if there was a drill point indent where the set screw had been? I'm assuming that the setscrew is kind of pointed at the end. I do believe there is another problem going on though. First thing I would do like you said check alignment. I'm sure somewhere on the internet there is a utube video or some instructions on how to do the alignment. About to put my new bigger racor water separator today and end my fuel problems. I hope.
Bruce

[deisher6]

Hey Bruce;
Hope the upgrade on your fuel system solves the problem.

When I  originally reinstalled the shaft, I used a drill to dimple the shaft where the set screws meet the shaft.  Those dimples were not in the vicinity of the old keyway. You can see tracks on the shaft left by the set screws where the shaft slid out of the collar.  It also looks as if the new keyway getting chewed up.

There was a thread on a C-27 that up engined.  I was hoping on a response explaining how the new engine was aligned.

I was wondering if I should replace the mounts at the same time, if I realign.  Am considering hiring out the job.

regards charlie

[Allure2sail]

Hi Charlie:
Not much I know about engine alignment but I think you unbolt the flange from the back of the transmition and measure the gap at the 0 degrees, 90 degrees, 180 degrees, and 270 degrees. Using a feeler gage to measure the gap at the four quadrants when they are all the same or at least within a thousand or two your home. What I wonder about is the engine is supported at four points. the front mounts would take care of the measurements at 0 degrees and 180 degrees by raising or lowering the engine on its mounts. I have to assume the rear mounts would give the lateral adjustment for making 90 degrees and 270 degrees and equal gap. One question I have on the process is what supports the flange once you unbolt it from the back of the trans. I have to assume that the weight of it would make it drop a little bit. Even with new packing in the stuffing box and a new cutlass bearing just the weight of it would make it drop. Perhaps you don't take the bolts out but just back them off a few turns to achieve a gap to measure with the feeler gage at the four points. There must be some clearance in the bolt hole for the bolt diameter that goes through it, so I question that process. Someone out there must know the procedure...best of luck.
Bruce
S/V Allure
P.S. Even with the new racor my problem continues.

[BobK]

Charlie,

As Bruce said you measure the distance between the two couple'rs with feeler gauges at the four quadrants.  however you only loosen the bolts - don't remove them.  The procedure is you loosen the bolts only enough to slip a feeler gauge between the plates.  At this point you move the engine via the motor mounts to match it to the prop shaft.  (this is assuming the shaft is not bent.) 

There should be some good youtube videos showing how to do this.  The tough part is thinking through which motor mounts to adjust.  Look at your motor mounts and make sure the rubber part has not started to disintegrate if so it will need to be replaced.

BobK

[Allure2sail]

BobK:
That all sound s familiar but I'm curious, there has to be a small amount of clearance for the four bolts. When you loosen up the four bolts to get a feeler gage in and measure at the four quadrants what do you do about the vertical sagging of the shaft and flange due to the bolt clearance. Is it so small it doesn't affect the measurements? Just thinking out load, 3 and 9 o'clock must be fine and give you a good side to side alignment. In retrospect it is a boat and not a space launch !!
Bruce

[Allure2sail]

Hi Charlie:
I was given a book on diesels by someone at my marina. It is by Nathan Caldwell and has a section on alignment, your pretty much on track.
Good luck with it...
Bruce