Aqualloy 17 vs 22

[Marshall Mahoney]

Sorry -- the price difference begs the question... I've called 4 machine shops in the New Orleans area (including Bayou Machine -- thanks Danny) and they all stock Aqualloy 17 and make a lot of shafts for the commercial shrimping and oil industry. They get very few requests for 22 and when they do, the cost is literally twice as much (shipping is a bid factor). I fish in salt water but dock in Venice -- fresh water. The boat sits idle for extended periods of time so there is the possibility for crevice corrosion -- but less since the boat docks in fresh water. I get very few if any barnacles on the shaft but lots of algae and some kind of calcium deposits which may become corrosion sites as well. Cheapest place I found for 22 is Deep Blue Yacht Supply on line at approx. $1000 per shaft...

Have to say I'm leaning toward 17. Somebody talk me out of it!.

A total shaft length question- I measure 78 inches from the coupling to the back of the strut. Plus the standard taper and thread length. How much should I add to ensure I get .8 x the shaft diameter between the strut and the prop? What's throwing me is the prop does not seat at the start of the taper (which I thought was odd since seating further down the taper would not take advantage of the full shaft thickness -- and may have prevented failure in the first place).

[micky]

Check with General Propeller in Fl. It was the cheapest of all including Deep Blue Yacht. I was between Aquamet 19 and 22 and the difference was only $200.

[Tony Meola]

Marshall in 2008 when I was repowering the 22 was going for $1200 a shaft. So the pricing you received is competative.

[Carl]

17 is the strongest and least corrosion resistant...great for commercial boats alway on the run.
Extra strength sometimes allowed for going a shaft size down for added savings, doesn't help if your already setup for a size.

19 has more corrosion resistance, almost as strong.

22 has the most corrosion resistance.



Problem is the shaft pits when sitting idle in the cutless where you cannot see.
The pits eat up the bearing, if and when it gets bad enough and of course the pits reduce strength.


Its a boat, its a trade off.
Around here corrosion and idle boats are the problem, mostly its the idle boats and dock electric issues...for that reason 22 is all we ever sold, unless otherwise requested.


If it were me, I'd ask guys around you what they are using...see what shaft life is like.
Fresh water is an unknown factor to me so can't answer.

17 up here is a 5 year shaft more or less depending...not much of a savings if having to replace.
But on a boat running 7 days a week when they expect a shaft to go every few years...22 does not pay.

I'd get you a number, but shipping tosss it al out...1k is close.


Small end of prop should overhang shaft by 1/16-1/8" or so when locked up. Both the small end of taper on shaft and prop are what get measured for exact size.
The length of prop hub dictates where the back end of hub stops along the taper.
Longer hub goes back further, you size length from start of taper, not back of wheel.

Take a look at link below to check me...

If you have:

1-3/8" shaft, the length from start of taper to the end of shaft is 6-1/8"

1-1/2" shaft, the length from start of taper to the end of shaft is 6-11/16"


http://www.pacificmarine.net/engineerin ... -shaft.htm

[Marshall Mahoney]

Thanks , as usual for the feedback. Looks like the price of fishing just went up...

[Carl]

The only thing that goes down in price is something I want to sell.