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Prop shaft play

Tracygold said:
I removed the prop on my alphaone drive
Notice in and out play on the shaft. How much is too much.
Click to expand...

The Alpha 1 prop shaft floats, so to speak.
When in FWD gear, the Dog Clutch sliding sleeve couples the shaft to the FWD driven gear.
The prop shaft's forward thrust is then stopped by it's contact with the forward gear.
The FWD gear's bearing takes the thrust load.

Apparently Merc suggests that between .040" and .060" in/out play is acceptable.

Merc A drive prop shaft in out play.jpg



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Again, If no issues prior to removing prop no issue to be worried about.

He is not reporting a problem.

If you throw out a specification, what possibly could he do to adjust?

PKR I believe you are incorrect again due to your lack of Mercrusier experience.................



That would require a complete tear down of the lower gear case and the Thrust washer between reverse gear and the clutch dog would need review/replacement[FONT=Verdana,Arial,Helvetica,sans-serif]. [/FONT][FONT=Verdana,Arial,Helvetica,sans-serif]Thrust spacer / 23-824108

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Jack, relax and enjoy the forum.
Don't be threatened by high post counts.... they mean nothing other than one's contributions to the forum.

If you disagree with a member, politely post why you disagree.
Explain your position and as to why you disagree, and do so in an adult like and polite manner.

kghost said:
Again, If no issues prior to removing prop no issue to be worried about.

He is not reporting a problem.
True! The OP is asking if there is a problem!

If you throw out a specification, what possibly could he do to adjust?
Haven't you attempted to explain that below *** ?


PKR I believe you are incorrect again due to your lack of Mercrusier experience.................
Take a closer look at the direction and path of the propeller thrust that is being transferred forward to the gear case!

Propeller provides forward thrust against the propeller shaft.
Propeller shaft transfers thrust forward.
The shoulders on shaft and FWD gear transfer the thrust to the FWD gear bearing arrangement.
FWD gear bearing arrangement transfers thrust to the gear case.
It's that simple!

Merc A drive prop shaft thrust path.jpg

***That would require a complete tear down of the lower gear case and the Thrust washer between reverse gear and the clutch dog would need review/replacement.
Thrust spacer / 23-824108

Click to expand...


 

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from merc manual 6
click to enlarge


Screenshot-2020-12-09-06-Drives-R-A1-83-90-pdf-2.png


 
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I've never seen a publish spec for prop shaft axial end play...as long as the gear backlash settings are in spec, the axial play shouldn't matter...
 
Reasonable understanding might prompt a boat owner to suspect a looming failure at a certain point here. That's all the OP is asking. If end play is approaching 1/10th of an inch, then something is wearing out. This design doesn't have an indestructable thrust bearing. Excessive end play cannot be ignored, gentlemen.
Yes....agreed ......number of posts is important but not always an accurate measurement of the experience, knowledge, and intelligence.
 
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.............
timguy said:
..............................
Yes....agreed ......number of posts is important
Although I can partially agree with that, I'd rather see good content than post counts.

but not always an accurate measurement of the experience, knowledge, and intelligence.
I believe that we can measure a person's experience by how well and thoroughly they write out their explanation.

When we use the correct terminology, sentence structure, spelling and grammar, and use good illustrations, we are able to convey our thoughts more effectively.
Click to expand...
 
""Jack, relax and enjoy the forum.
Don't be threatened by high post counts.... they mean nothing other than one's contributions to the forum.

If you disagree with a member, politely post why you disagree.
Explain your position and as to why you disagree, and do so in an adult like and polite manner.""


I did explain my position!
 
Back to the OP, every well working, Alpha gen one or two I’ve had had at least 1/8” in and out play in prop shaft. Years back I asked my mechanic too as it doesn’t seem right. Zero side play on the shaft . If you keep lube it in and change it annually will last a long time
 
Okay just found this......direct quite from Mercruiser shop manual.
 

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Honestly....my manual doesn't give prop shaft end play.....so not sure what manual this is referencing. If prop shaft shows .007 or more at end of splines while rotating against your dial indicator, then it is bent beyond acceptable limit.
 
timguy said:
Honestly....my manual doesn't give prop shaft end play.....so not sure what manual this is referencing. If prop shaft shows .007 or more at end of splines while rotating against your dial indicator, then it is bent beyond acceptable limit.
Click to expand...

Tim, Tracygold (the OP here) suggests that he sensed FWD/AFT or In/Out play......... not Run-Out!
Those are two entirely different forms of either "within" or "out of" specs!

Tracygold as per post #1 said:
I removed the prop on my alpha one drive
Notice in and out play on the shaft. How much is too much?
Click to expand...
 
Right, I understand that, just wanted to throw that out there as it showed up in the specs. Normally if the shaft is bent, other problems may show up, but end play as you mentioned, is not a huge consideration. As also mentioned, more commonly, when end play becomes excessive, it might show up in another speck like backlash forward gear/to pinion first. If motor is often run in reverse, then the forces of course, involve another bearing. If both wear enough, excessive pinion to gears clearance may translate to considerable end play as the "transmission" is wearing out. It's much more likely, however, that gears will fail before end play is even considered. We can notice the shaft end play might also become excessive if the shoulder that carries thrust to the bearing should gauld and fail. This would result in very few wear particles in the gear oil.....unlike bearing or gear failure.
 
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Now.... therefore to quote Jack in post #2.....fairly "historical" post here : "Too much would cause failure"! Very true.......But I might add this: " Failure would cause too much"!
 
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