How much should a drive shaft move, forward/back?

[Fire3456]

I have a 2001 sportster LE w/single 951.

My Questions:

How much "forward/backward" movement should there be in a drive shaft?
How can I get the engine to the correct depth?
I know there is an alignment tool that I've read about. I'm looking to order that, but that seems to measure the correct angle (which I DO want to also do).

My Details:

I bought this boat (nightmare) used. The previous owner said the motor had been rebuilt. It did start right up and ran smoothly late winter when I looked at it (out of water). It seemed to run fine, last summer, for a month. Then the Drive Shaft splines stripped on the PTO side. (in the middle of the Mississippi)

After checking out everything from the engine back, I found that the drive shaft had no bumper on the PTO end. I'm hoping that was the problem (along with total neglect from the previous owner). When I took everything apart, the prop shaft and bearings had been rusted and pitted terribly. I took the complete pump housing to a dealer because it had been so rusted I couldn't start to replace all that) So I replaced EVERTHING (but the housings).

I had everything together. While pushing back the new support ring and new carbon seal, to insert the "C" clip, the drive shaft moved backwards, maybe 1/2 inch, more or less. I was able to put the "C" clip on just fine. It just seemed like it was a lot of movement, because what had originally been the problem was the stripped splines on the PTO end of the drive shaft. (I replaced the drive shaft w/bumpers, and PTO). I had everything replaced in the pump housing (shaft, bearings, etc).

So everything from the engine back, is new except the housing. I don't want the splines to strip again. Then I remember the guy who sold it to me said the engine was rebuilt. (It was NOT rebuilt, and if so, it was installed rather 1/2 assed and a cylinder had rather low compression but within tolerance).
I've read quite a few posts, talking about Engine alignment and depth. Now I'm thinking that my Engine Depth may be off.

See Questions at the Top!



Thanks for any advice or help!!!

 

[POPPS]

Those rubber dampers get squished all the time,,,their presence or non-presence has nothing to do with splines,,,that usually occurs from engine misalignment…or a blocked pump and powering the motor through the blockage

 

[wernerml]

My drive shaft only moves back and forth less than 1/4". When I pumped a little grease in the PTO it "inflated" the rubber boot and pushed the shaft toward the stern. When I replaced the bumpers they were pretty deformed/compressed.

I am the second owner of this boat, the first owner was a work mate and we are both engineers at an automotive supplier. Really not much room around the screws for the engine to be installed more than ~1/8" off front to back, unless they removed the engine mounts from the hull.

Mine has a couple of shims between the engine mounts and the engine on both sides. I have always been very careful to put the shims back where they came from.

 

[Fire3456]

Thanks for all the input!! I know, for next time, (hopefully there won't be one?) to check the alignment before I install the driveshaft. Because I have completely finished assembly of the project, I decided to "hope" the engine wasn't removed and just run the boat 'as is'.
I've had the boat out several times, for hours at a time. So far, so good. No vibrations. No obvious signs of misalignment. I've learned a lot thanks to all the input.
THANK-YOU!