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Aquamatic Propellers - Fitting a Long Hub Propeller to A Short Hub Shaft

Jeff, all due respect to you here. I just want to add a bit of clarity to this.

Aquamatic Propellers - Fitting a Long Hub Propeller to A Short Hub Shaft


I can tell you for certain (technically speaking and with 24+ years experience), that unless you are comparing them side/by/side prior to being installed in the lower unit gear case, this Long/Short prop shaft business is a misnomer.
With the correct and necessary spacer/line cutter installed, there is no such thing as a short or long AQ series s/p drive propeller shaft,
I say this because we cannot install either length propeller hub without the correct spacer/line cutter for the prop shaft.
Once the correct spacer/line cutter has been installed, the net amount of exposed propeller shaft and splines is equal between the different drive models.
Now and ONLY now can we install the propeller and spinner.

( 250, 270, 275 = the short spacer/line cutter.... whereas the 280, 285 290 = the long spacer/line cutter..... and with no exceptions. )


I go through Aquamatic props regularly. We like to explore remote areas that are often quite shallow. My 250 outdrive takes the short hub propeller – the one where the bendy tab locks the cone.

Yes, all 250 lower units must use the short hub propeller.
Or..... in order to use a long hub propeller, you could install a 275 lower unit, and you will have the internal threads necessary for the spinner and center keeper bolt.


The place that I’d been getting the short hub props no longer handles them. I bought a long hub prop – the one that uses a bolt into the end of the cone to lock it, just to see if I could make it work. I couldn’t come up with a solution. That long hub propeller needs a threaded shaft and mine isn’t threaded.

I believe that you meant to say "Internally" threaded shaft for the center keeper bolt!
In my image below, I show an X dimension.
When the correct spacer/line cutter is installed (as it must be), this X dimension is the same between the 250/270/275 and the 280/285/290 propeller shafts.
 

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  • Prop shaft lengths explained.jpg
    Prop shaft lengths explained.jpg
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Jeff, the factory internal threads are finished/plated. If you attempt to drill and thread your 250 propeller shaft for internal threads, you will be cutting into carbon steel. Bare carbon steel threads are going to rust/corrode. This will make removing the center locking bolt difficult, if not impossible.

It would be cost effective to pick up a newer lower unit of the correct ratio...... 275, 280 or a 290 s/p drive lower unit.
The 280 or 290 style trim fin/torque tab is must more effective over that of the trim fin/torque tab of the 250/270/275.

The 2.15:1 (4 cylinder) and the 1.89:1 (in-line 6 cylinder) ratios are a dime/dozen.
The 1.61:1 (V-8 ratio) will cost you more.

The shimming procedure is very straight forward.



And BTW, regarding the AQ series drives, most all of the threads that you'll have to deal with are US NC threads........ Not Metric!



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I was so confused about all that rhetoric that I was afraid to drill my non-threaded short hub shaft, but once I did I am one happy camper. PM me if you'd like me to send you my drilling mandrel so you can do your own.
 
Jeff, I am glad that you are happy with the results.
I am also curious as to whether or not you will have any trouble with the "now exposed" carbon steel threads regarding rust!


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RicardoMarine said:
Jeff, I am glad that you are happy with the results.
I am also curious as to whether or not you will have any trouble with the "now exposed" carbon steel threads regarding rust!


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Click to expand...

So far no trouble with the new threads. I don't even have a bolt in the cone now because I'm using a short hub prop with bendy tabs. The boat is kept on a trailer and sees mostly freshwater use but has spent a week in saltwater.
 
Hi i have a 280 lover unit @ the moment I have a 15*21 prop and need to go a little smaller to gain arround 500rpm on engine, now at my garage I have a 14*19 but it is a short shaft type, is there a way to fit it at least for testing? I was thinking of machining an Aluminium spaces to a correct size and then place it behind the conic nut in front. Have anyone done this before?
 
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