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Old 08-12-2014, 07:00   #31
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Re: Fitting a Prop

Always coat your prop, that's one the the best ways to keep them alive for much longer time.
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Old 08-12-2014, 07:03   #32
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Re: Fitting a Prop

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Originally Posted by Exile View Post
Recently I had an experienced diver remove my prop for re-pitching. After reading this thread, I think I'm finally understanding why he declined to reinstall the prop with the boat in the water. Although I had this done once, it doesn't sound like the greatest idea. Maybe fastbttms or another one of the pros can comment.
I have been installing Max Props underwater for years. It has never been a problem for me. I have a 100% success rate and have never lost a part primarily because I come to the job prepared with the right tools and I know what I am doing. The only reason to avoid doing this would be because your diver isn't prepared or doesn't know what he his doing.

The bottom line is that there is almost no reason to ever haul a boat to remove or install any prop, be it fixed, folding or feathering.
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Old 08-12-2014, 10:35   #33
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Re: Fitting a Prop

I've always use a sparse amount of lube on the taper and key. By that I mean apply it and wipe it off.... just leaving the surface a little oily.
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Old 08-12-2014, 10:47   #34
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Re: Fitting a Prop

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I'm not arguing, but if there is no need, why is it there? I've seen keys that were a little too tall and or not seated properly cause problems as the prevent the bore from properly seating on the taper, so it would seem that if it's not needed, the proper thing would be to not install it.
I believe you are supposed to install the prop without the key, mark the shaft, remove the prop, install it again with the key in place and make sure it goes on as far as the mark. This means the key is where it is supposed to be and not keeping the prop from fitting properly on the shaft.
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Old 08-12-2014, 10:56   #35
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Re: Fitting a Prop

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Originally Posted by fstbttms View Post
I have been installing Max Props underwater for years. It has never been a problem for me. I have a 100% success rate and have never lost a part primarily because I come to the job prepared with the right tools and I know what I am doing. The only reason to avoid doing this would be because your diver isn't prepared or doesn't know what he his doing.

The bottom line is that there is almost no reason to ever haul a boat to remove or install any prop, be it fixed, folding or feathering.
Interesting! I wasn't expecting that answer after my diver recently declined to reinstall my prop. He cited "liability" reasons, but he's also not a full-time pro. I think it's a sideline for him and it could be that most of his work is cleaning bottoms vs. dealing with props. Anyway, thanks for responding.

Your own experience also confirms that grease, oil, lapping compound, or any other sort of prep is unnecessary. I assume it's hard to apply any of that underwater!
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Old 08-12-2014, 11:31   #36
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Re: Fitting a Prop

And just to put the cat amongst the seagulls, the thin nut goes on first, then the full nut up against it.
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Old 08-12-2014, 11:40   #37
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Re: Fitting a Prop

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And just to put the cat amongst the seagulls, the thin nut goes on first, then the full nut up against it.

Jam nut & king nut
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Old 08-12-2014, 11:48   #38
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Re: Fitting a Prop

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Jam nut & king nut
You put the transmission in gear before torquing the nuts so the shaft won't spin? Do the torque values essentially come down to as tight as you can get both nuts? I assume you want a second wrench to hold the jam nut before putting the hurt on the king nut?

I've never said "first time for everything" as much as I have since owning a boat.
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Old 08-12-2014, 11:48   #39
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Re: Fitting a Prop

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Jam nut & king nut
Yep !!--was trying to not complicate things
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Old 08-12-2014, 11:54   #40
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Re: Fitting a Prop

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You put the transmission in gear before torquing the nuts so the shaft won't spin?
No. I immobilze the prop by blocking it with a piece of lumber between the strut and rudder.

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Do the torque values essentially come down to as tight as you can get both nuts?
Yes

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I assume you want a second wrench to hold the jam nut before putting the hurt on the king nut?
No. The jam nut is tightened, then left alone as the king nut is tightened down on top of it, deforming the jam nut very slightly (if my understanding of the mechanics involved is correct.).
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Old 08-12-2014, 13:23   #41
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Re: Fitting a Prop

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No. I immobilze the prop by blocking it with a piece of lumber between the strut and rudder.



Yes



No. The jam nut is tightened, then left alone as the king nut is tightened down on top of it, deforming the jam nut very slightly (if my understanding of the mechanics involved is correct.).
I wonder if it may be prudent to replace both nuts each time?
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Old 08-12-2014, 13:36   #42
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Re: Fitting a Prop

In the meantime lets shake hands and agree to differ.
If the prop is hard to get off, use two hammers simultaneously gently tapping each side of the boss, turn a half turn, repeat and hey presto the prop will pop off.
Now let's go get another beer and crack a few jokes !
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Old 08-12-2014, 13:47   #43
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Re: Fitting a Prop

Yes correct, two wrenches not needed. The way I see it is the king nut takes the load off the jam nuts' fewer threads. So the jam nut....."jams" the larger king nut. And the king nuts' longer threads carry the load.

May be taking my prop shaft out soon, so a topic of concern recently for me. Since it's only been 4 years of boat work so far there is always something new to learn. Interesting how there is always eight ways to do anything. And people have been doing it all those ways "forty years". :-)
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Old 08-12-2014, 13:49   #44
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Re: Fitting a Prop

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I wonder if it may be prudent to replace both nuts each time?
Unnecessary, IMHO. Prop nuts do not fail except from corrosion.

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If the prop is hard to get off, use two hammers simultaneously gently tapping each side of the boss, turn a half turn, repeat and hey presto the prop will pop off.
Beating on the prop itself is going to certainly damage it. The proper (and only) tool that should be applied to a prop to remove it is a prop puller.
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Old 08-12-2014, 14:06   #45
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Re: Fitting a Prop

On the lapping process..... machining a taper can be a bit tricky. When mating a prop and shaft that haven't seen each other before it could be prudent to lap them.

It serves to verify a proper fit and refine the mating surfaces, increasing the contact surface area. Not so necessary for a R and R of an existing setup.

Granted my past experience is hand fitting roller crank bearings and valves in antique engines. Not props.
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