Trying to identify lower unit and correct HUB

Allmand

Petty Officer 2nd Class
Joined
Aug 23, 2010
Messages
124
Hello,
I have a 1968 pre-alpha drive. I know the upper is pre-alpha and the lower WAS pre-alpha before I had it rebuilt. But the mechanic put on a different rebuilt lower because he said mine wasnt worth fixing. So now not sure about the lower. It has been freshly painted so I cannot see any numbers on it. Where are the number located on the lower? The outdrive has been great and has made a big improvement in the performance of the boat as long as the prop stays on.

I looked inside and he replaced just about everything. But it came back with a different type of prop shaft. It has the larger lock nut threads rather than the smaller threads that evey flo-torq hub I have purchased has. I had to go to home depot to get a bolt with the correct threads. Anyway, I bought a new prop (Mercury 78116A45 15 pitch). The original props that I had all had the pressed hubs. With this new prop shaft and prop I cannot find a hub kit to work correctly. I bought the standard flo torq II kit for mercruiser stern drives alpha/alpha 1 less than 400HP, but the hub never works correctly. The prop goes too far down into the bell of the housing and rubs real bad. And when I tighten the prop bolt the prop gets harder to turn, more resistance with each turn of the wrench. Strange. So I put two thrust washers behind it and the prop is now at the right depth, but I still have the problem of not being able to tighten the prop bolt all the way, because if I do the pront wont spin. So I have a loose lock nut that is only being held in place by the tab washer. I know that cant be right.

I looked up the prop online that I ordered and have ordered the exact hub kit that mercury makes for that prop (835257k-1) but it "looks" the same as all the others that I have bought. Could this be a new lower unit or a newer or different style prop shaft that requires a different hub kit? I have looked at many outdrives and the prop shaft threads have always been the same size. this is the first time I have seen these large/wider threads.

Any help is appreciated.
 

ziggy

Admiral
Joined
Jun 30, 2004
Messages
7,473
Re: Trying to identify lower unit and correct HUB

Where are the number located on the lower?
i'm not aware of anywhere the s/n is stamped on a lower. on the upper, yes, but not the lower.


is the thread of the prop nut 3/4-16? that would be the norm. in s/m #1 i see no other option even.

So I put two thrust washers behind it and the prop
there are two different thickness thrust washers. my '72 165 w/ a fan blade type prop, not flotoruqII, required the thick thrust washer. when i switched to a flo torqueII prop, i had to use the thinner thrust washer. maybe go to your merc. dealer and get the thick thrust washer? or here.

maybe ya need to id your lower. http://www.mercstuff.com/drive_id.htm that might help, might not.
best i can do for ya.. got pics?
 

Allmand

Petty Officer 2nd Class
Joined
Aug 23, 2010
Messages
124
Re: Trying to identify lower unit and correct HUB

i'm not aware of anywhere the s/n is stamped on a lower. on the upper, yes, but not the lower.


is the thread of the prop nut 3/4-16? that would be the norm. in s/m #1 i see no other option even.

there are two different thickness thrust washers. my '72 165 w/ a fan blade type prop, not flotoruqII, required the thick thrust washer. when i switched to a flo torqueII prop, i had to use the thinner thrust washer. maybe go to your merc. dealer and get the thick thrust washer? or here.

maybe ya need to id your lower. http://www.mercstuff.com/drive_id.htm that might help, might not.
best i can do for ya.. got pics?

Thanks for the reply....I am not to savy on the exact measurments of threads. I will post some pics tonight of the lower and the threads. Thanks for the link, I will check it out.
 

Allmand

Petty Officer 2nd Class
Joined
Aug 23, 2010
Messages
124
Re: Trying to identify lower unit and correct HUB

And yes, it could be that I am using the wrong thrust washer, would these also cause the shaft to tighten up as I tighten the lock nut down? Just two or three turns and the prop nor the shaft will move withouth putting some muscle into it.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,095
Re: Trying to identify lower unit and correct HUB

Ayuh,.... Donno what yer doin' wrong, But,...
Merc propshafts are all the Same, from the MC-1, through the Alpha, Gen.II...
 

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: Trying to identify lower unit and correct HUB

And yes, it could be that I am using the wrong thrust washer, would these also cause the shaft to tighten up as I tighten the lock nut down? Just two or three turns and the prop nor the shaft will move withouth putting some muscle into it.

If the thrust washer diameter/taper for the prop shaft is too large, as you are tightening it can be pushing against the housing.

Time to talk to your mechanic and find out what he did to your drive.
 

Allmand

Petty Officer 2nd Class
Joined
Aug 23, 2010
Messages
124
Re: Trying to identify lower unit and correct HUB

If the thrust washer diameter/taper for the prop shaft is too large, as you are tightening it can be pushing against the housing.

Time to talk to your mechanic and find out what he did to your drive.

I checked and its for sure and Mercury pre-alpha 'R' drive but this prop shaft has bigger threads than usual. I am not sure why. I was not able to take pics last night, but for sure will tonight and post. Please check back when you can to see what you think.

thanks again
 

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: Trying to identify lower unit and correct HUB

I checked and its for sure and Mercury pre-alpha 'R' drive but this prop shaft has bigger threads than usual. I am not sure why. I was not able to take pics last night, but for sure will tonight and post. Please check back when you can to see what you think.

thanks again

Per Bondo's response, I have no idea why you have different threads. Your mechanic should.

Different threads by themselves shouldn't cause the binding you are describing. The prop should be tight on the shaft, and it and thrust washer should not be touching the housing.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,095
Re: Trying to identify lower unit and correct HUB

I checked and its for sure and Mercury pre-alpha 'R' drive but this prop shaft has bigger threads than usual. I am not sure why. I was not able to take pics last night, but for sure will tonight and post. Please check back when you can to see what you think.

thanks again

Ayuh,.... Something is Very Wrong....
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,931
Re: Trying to identify lower unit and correct HUB

Sorry but that prop wont work with your unit ,you must use the pressed in hub style. The older Mercruisers had a "coarse" thread prop nut, a straight prop shaft so a tapered thust washer has no place to set and different drive shaft(spline count). You must use your original washer that set against square shoulder on bottom of propshaft.

B2.jpg
 
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