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barefoot
04-25-2009, 10:33 PM
These are directions to properly mate your new prop to the shaft taper. The prop is held on by the taper so it is essential that there is a proper fit to eliminate vibration and transmit power effectively without putting undue stress on the shaft. It is said that 70% of the torque is transmitted though the fit on the shaft and the rest through the key/keyway. I, for one, believe that it is actually higher. The proper fit on the shaft means that there will be no slop between the taper and the key.

Here’s what you’ll need:

-Prussian Blue to find high spots on shaft (available at Napa Auto Stores)
-Valve grinding compound (also available at Napa)
-Prop puller
-Wrench
-Key/Keyway
-Cotter pin
-Acetone or some type of cleaning solution

barefoot
04-25-2009, 10:35 PM
Start by removing the cotter pin. Loosen the Nylock nut or castle nut until there is roughly ˝ space between the prop and the nut. Use the prop puller and give the tightening bolt on the prop puller a few direct hits to loosen the prop from the shaft. If it doesn’t loosen, you may have to tighten and hit again. Once the prop is freed, remove the nut and the prop from the shaft.

Now that the prop is removed, clean the shaft with a scotch brite pad.

barefoot
04-25-2009, 10:36 PM
Put a light coat of the Prussian blue on the shaft to detect the high spots.

barefoot
04-25-2009, 10:38 PM
Slide the new prop on the shaft and rotate back and forth in an arch pattern. Where the blue wears away will indicate your high points. This is where you will work the grinding compound to get a proper lapped fit.

barefoot
04-25-2009, 10:39 PM
Next, clean the shaft of the Prussian blue and apply some grinding compound to the shaft. Slide the new prop on the shaft and work the prop in a back and forth in half motion turns. The grit will begin to smooth out during the lapping. When this happens, slide the prop off and redistribute the grit. Do this several times until it becomes smooth. Put another light coat of Prussian blue on the shaft to see if the high points have been removed. Add more grinding compound and continue lapping until the high points are removed. After you are finished, slide the prop off and the shaft will have a nice smooth mate finish. Clean the shaft with Acetone.

barefoot
04-25-2009, 10:41 PM
There should be a definite “line” where you lapped your prop to the shaft on the forward edge. Slide the prop back on and check this line. This is an indication of how far forward the prop should sit on the tapered shaft. Now remove the prop and insert the key in the prop shaft. The trick here is to fit the prop on the taper and not the key. If the prop is not on the forward lapped edge, it’s most likely bottoming out on the key. Remove the prop and slide the key down the shaft and try again. If the key overlaps the prop on the aft edge, the key must be moved forward up the shaft in order to allow room to tighten the nut.

If you are using a new key, it may require you to file one side of the key to fit snuggly in the prop shaft. (Note: the key should fit snuggly in the prop shaft. It should not fall out and conversely, it shouldn’t have to hammer in the shaft either.)

Now that the prop and key are in the correct position, tighten the nut snugly against the prop using 30 ft/lbs of torque. Install the cotter pin and bend the legs over the nut.

That’s it. You’ve now properly mated your prop to your shaft.

CantRepeat
04-25-2009, 10:57 PM
Great post, I had no idea there was so much involved in putting the prop on, correctly.

barefoot
04-25-2009, 11:08 PM
There was another site (that shall remain nameless while on an MC site :o) that had a post on the subject. We didn't have one here so I thought it would be helpful to write it as an FAQ.

Pretty straight forward to do...took me about two beers to complete :rolleyes:

thatsmrmastercraft
04-25-2009, 11:24 PM
Thanks for the efforts barefoot. This really shows the difference between doing a job and doing it right.

russlars
04-26-2009, 01:45 AM
There should be a definite “line” where you lapped your prop to the shaft on the forward edge. Slide the prop back on and check this line. This is an indication of how far forward the prop should sit on the tapered shaft. Now remove the prop and insert the key in the prop shaft. The trick here is to fit the prop on the taper and not the key. If the prop is not on the forward lapped edge, it’s most likely bottoming out on the key. Remove the prop and slide the key down the shaft and try again. If the key overlaps the prop on the aft edge, the key must be moved forward up the shaft in order to allow room to tighten the nut.

If you are using a new key, it may require you to file one side of the key to fit snuggly in the prop shaft. (Note: the key should fit snuggly in the prop shaft. It should not fall out and conversely, it shouldn’t have to hammer in the shaft either.)

Now that the prop and key are in the correct position, tighten the nut snugly against the prop using 30 ft/lbs of torque. Install the cotter pin and bend the legs over the nut.

That’s it. You’ve now properly mated your prop to your shaft.
That's a nice looking prop barefoot. Is that an ACME or an OJ? Thanks for the tutorial.:)

CantRepeat
04-26-2009, 06:39 AM
BTW: If you go into NAPA and ask for -Prussian Blue to find high spots on shaft (available at Napa Auto Stores) and the young lady doesn't know what it is, it might help to tell her it's gear marking compound.

barefoot
04-26-2009, 10:07 AM
That's a nice looking prop barefoot. Is that an ACME or an OJ? Thanks for the tutorial.:)



ACME 515...13 x 12. I have a 1:1 trans and a 1 1/8 bored shaft. I went from what I believe to be the stock OJ 3 blade 13 x 13. From what I've been reading, a CNC'd prop is a must. Should get more hole shot, top end, and also an improved wake. That's what I'm hoping it will do the most...I have a bump from the prop wash at 15 off that bothers me.

Now, I'd like to get it on the water if this rain stops!

TMCNo1
04-26-2009, 02:26 PM
BTW: If you go into NAPA and ask for -Prussian Blue to find high spots on shaft (available at Napa Auto Stores) and the young lady doesn't know what it is, it might help to tell her it's gear marking compound.

Or valve grinding compound.

Chicago190
04-26-2009, 02:53 PM
Thanks for the helpful post. Here is my new CNC OJ XMP 13.7x17.5 4-blade to replace my original 14x18. I am ready for it to be summer already.

russlars
04-26-2009, 03:02 PM
ACME 515...13 x 12. I have a 1:1 trans and a 1 1/8 bored shaft. I went from what I believe to be the stock OJ 3 blade 13 x 13. From what I've been reading, a CNC'd prop is a must. Should get more hole shot, top end, and also an improved wake. That's what I'm hoping it will do the most...I have a bump from the prop wash at 15 off that bothers me.

Now, I'd like to get it on the water if this rain stops!
Let us know how it works out for you.

CantRepeat
04-26-2009, 03:16 PM
Or valve grinding compound.

-Prussian Blue is not valve grinding compound. It's gear marking compound used to set up gears in axles or in this case find high spots on your prop shaft. The attached photo is the yellow gear marking compound. Some people prefer the blue.

barefoot
04-26-2009, 03:23 PM
Duh...I feel like a dumb a$$

Good news is that it's official comfirmed that I have a 1.52:1 tranny...

...bad news is...prop's the wrong size...

You might be asking (much like I am) why I didn't know that. Beleive me...I'm beating myself up for it too. I would have bet my boat it was a 1:1.

TMCNo1
04-26-2009, 03:49 PM
-Prussian Blue is not valve grinding compound. It's gear marking compound used to set up gears in axles or in this case find high spots on your prop shaft. The attached photo is the yellow gear marking compound. Some people prefer the blue.
Sorry, I just missed the valve grinding compound mentioned in post #1.

JohnnyB
04-26-2009, 03:51 PM
OK, I'm a dumb@$$, why is using this process before mounting your prop important???

Chicago190
04-26-2009, 04:17 PM
Duh...I feel like a dumb a$$

Good news is that it's official comfirmed that I have a 1.52:1 tranny...

...bad news is...prop's the wrong size...

You might be asking (much like I am) why I didn't know that. Beleive me...I'm beating myself up for it too. I would have bet my boat it was a 1:1.

I think you'll want to go with a 4-blade prop for a Powerslot trans.

barefoot
04-26-2009, 04:53 PM
OK, I'm a dumb@$$, why is using this process before mounting your prop important???



Check the first post, but this process insures that your new prop will fit on your shaft perfectly. Essentially, it's overkill. We love our boats and we'll take the extra time to do it right.

barefoot
04-26-2009, 04:55 PM
I think you'll want to go with a 4-blade prop for a Powerslot trans.



I've heard varying thoughts on this. I'll talk to the boys at ACME and see what they say...

JohnnyB
04-26-2009, 09:18 PM
Check the first post, but this process insures that your new prop will fit on your shaft perfectly. Essentially, it's overkill. We love our boats and we'll take the extra time to do it right.

I remember this from the manual in my '92 ProStar but no mention is made in my 2004 manual....

Chicago190
04-27-2009, 10:20 AM
I remember this from the manual in my '92 ProStar but no mention is made in my 2004 manual....

Had Mastercraft switched to splined shafts by 2004?

TMCNo1
04-27-2009, 10:55 AM
why is using this process before mounting your prop important???
As it was explained to me, mating the two surfaces, the shaft and the inside of the hub, the pressure and the forces of the prop on the shaft pushing forward, spreads the load over the entire surface of both the shaft surface and the inside hub surface and not just at the various high spots on both surfaces. I have found that it also makes removing the prop at a later date much easier, rather than the high spots on each surface anchoring only parts of both surfaces and putting them in a bind. I also helps to apply a very light film of marine anti corrosion grease to both surfaces prior to installing the prop so it will come off at a later date much easier.

JohnnyB
04-27-2009, 07:41 PM
Had Mastercraft switched to splined shafts by 2004?

Ummm....good point! No wonder I don't remember doing this on my 2004 :confused:

EJ OJPROP
04-29-2009, 10:29 AM
I've heard varying thoughts on this. I'll talk to the boys at ACME and see what they say...

We at OJ have some thoughts on the issue as well. Be happy to discuss it with you and let you try a prop or two.

Eric @ OJ PROPS
800-359-9730

Chicago190
05-15-2009, 09:50 PM
I installed my prop per the directions above and had no problems. I'll follow up tomorrow or Sunday once I've had a chance to get on the lake.