Post Service X-Star Questions

[badinlake]

2019 X-Star just got back from new Mastercraft dealer for service. I can tell they are bending over backwards to give gold level service. But....

Part of the service they did involved the replacing the strut that holds the shaft and the shaft.

I was a little puzzled when they called about my Acme prop and how it didn't fit correctly on the shaft. I sent them a photo of my original prop. They loaded a prop from a new x-star and i brought my to swap.

2 things - first, i noticed a considerable shudder upon acceleration that persists at plane/speed.

Second, i noticed the prop they put on was a 18x16 846 4/21, and my original prop was an 18x16 846 4/19.

Did the shafts change and maybe they didn't know it (change in part from Mastercraft)? Would that cause my shudder?

I've got a couple weeks before I am really needing to hit the water and I'm trying to help this new Mastercraft service person along in diagnosing.

[badinlake]

If it helps, it looks like the new shaft is:

MC-205345A SHAFT-52.5"x1 1/8"x5" LSA ENGINE '11-'12 / 7.4 '12-'14 AQUAMET 22 W/LRG NUT

MC-200195 STRUT-XSTAR '18

[gwozhog]

Sounds like your prop is slightly bent. It does not take much to get that subtle vibration. Here is an easy test you can do to check an acme prop. https://www.youtube.com/watch?v=_uVXh9sJt4w

[badinlake]

Bent prop may be the case, but supposedly they pulled it off a new boat. I am curious about the change in size too. I will post an update when resolved - and hopefully it was just a bad prop.

[Tsumi]

The 4/19 and 4/21 are most likely date codes. 18x16 is the size, and 846 is the model number. All OJ 846 props should be identical.

[FourFourty]

The 4/19 and 4/21 are most likely date codes. 18x16 is the size, and 846 is the model number. All OJ 846 props should be identical.

This is correct. Those are just date codes. One prop was made in april 2019, and the other in april 2021. The props (18x16 846) are both the same.

[badinlake]

OK - so more information...

I got back out to the lake and yes, it looks like the prop they supposedly put on from a new Xstar has dings in it - so that's most likely where my vibrations are coming from. But - I found out more...

So, I still was confused that the dealer said my OJ prop "didn't fit" on the shaft. Turns out my after market ACME prop is 18x17.5, 1 1/8", 3289. The prop they put on is OJ 18x16 MF WP 846.

I tried to put the ACME prop back on, and the dealer is correct - it does not fit correctly. I sides much further up the shaft, exposing the splines at the front of the prop - which means the prop cannot be secure on the shaft.

I need to get my original prop from the dealer, but I am assuming they may have put on the wrong shaft - is that possible?

[jpwhit]

Are you sure you have the prop numbers correct? The 3289 is a left hand rotation prop and the 846 is a right hand rotation prop? Why was the shaft replaced? Was the transmission changed as well?

[badinlake]

Wow - even more information! the shaft strut had some funny wear on it, so dealer replaced under warranty. I'm assuming he did the shaft as part of that warranty work too... I will keep you posted. Here is a photo of the funny wear.

[edwin]

That funny wear sure looks like the prop moving up the shaft and making contact with the strut...probably a direct result of the ACME not fitting.

[jpwhit]

Or the splines on the original shaft were not machined correctly, they wallowed out the splines in the prop and then it moved forward and damaged the strut. If that's the case, then the damaged prop also wouldn't work on the newly replaced shaft.

But none of that explains the left vs right prop rotation.

[FourFourty]

Or the splines on the original shaft were not machined correctly, they wallowed out the splines in the prop and then it moved forward and damaged the strut. If that's the case, then the damaged prop also wouldn't work on the newly replaced shaft.

But none of that explains the left vs right prop rotation.

Or.......... Someone installed the prop nut (when they installed the ACME prop) with an impact gun, and torqued it to 30-40 ugga-duggas............. and forced the prop too far up the shaft. Seen that before. Id be curious what the back of the hub looks like on the ACME 3289. I have run the 3289 on three XStars now (2018, 2020, and 2022), and it fit perfect.

[badinlake]

Here's the summary - and thanks to the forum for helping me through...

Yes, the rear end of the splines on the ACME prop are gone. Not sure how this happened, but I do know before I sent my boat in for service the prop was snug - now it goes about 1/4" past the shaft threads, so it won't fit. Anyone have any suggestions for reworking the ACME prop or is it just dead?

The issue w/ the ACME prop muddied the water in my head - good advice from people here, separate out the problems and look for the simple.

The prop the dealer put on was dinged - after putting on a brand new prop, all runs great.

[jpwhit]

Anyone have any suggestions for reworking the ACME prop or is it just dead?

I doubt it's possible to repair the splines, but call ACME and ask.

[FourFourty]

I doubt it's possible to repair the splines, but call ACME and ask.

You would think it would be all done, but I have seen them fix some crazy bad things on props. They might be able to fill with new material and broach new splines in it again. You might be right, and it may be junk. But it wouldnt surprise me if they could fix it.